CN100371298C - Grain oriented ceramics and production method thereof - Google Patents
Grain oriented ceramics and production method thereof Download PDFInfo
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- CN100371298C CN100371298C CNB2005100980547A CN200510098054A CN100371298C CN 100371298 C CN100371298 C CN 100371298C CN B2005100980547 A CNB2005100980547 A CN B2005100980547A CN 200510098054 A CN200510098054 A CN 200510098054A CN 100371298 C CN100371298 C CN 100371298C
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Abstract
To provide a grain oriented ceramic capable of exerting excellent piezoelectric properties, a production method thereof, and a piezoelectric material, a dielectric material, a thermoelectric conversion element and an ion conducting element each using the grain oriented ceramic, there is provided a grain oriented ceramic comprising, as the main phase, an isotropic perovskite-type compound which is represented by formula (1): {Li<SUB>x</SUB>(K<SUB>1-y</SUB>Na<SUB>y</SUB>)<SUB>1-x</SUB>}(Nb<SUB>1-z-w</SUB>Ta<SUB>z</SUB>Sb<SUB>w</SUB>)O<SUB>3 </SUB>in which x, y, z and w are in respective composition ranges of 0<=x<=0.2, 0<=y<=1, 0<=z<=0.4, 0<=w<=0.2 and x+z+w>0. The main phase comprises a polycrystalline body containing from 0.0001 to 0.15 mol of any one or more additional element selected from metal elements, semimetal elements, transition metal elements, noble metal elements and alkaline earth metal elements belonging to Groups 2 to 15 of the Periodic Table, per mol of the compound represented by formula (1). A specific crystal plane of each crystal grain constituting said polycrystalline body is oriented.
Description
[ technical field ]
The present invention relates to a grain-oriented ceramic containing no lead in chemical components and a method for producing the same, and also relates to a piezoelectric element, a dielectric element, a thermoelectric conversion element, and an ion-conducting element.
[ background Art ]
Piezoelectric materials having a piezoelectric effect are classified into single crystals, ceramics, thin films, polymers, and composite materials (composite materials). Among these piezoelectric materials, piezoelectric ceramics have been widely used in the fields of electronics or mechatronics, such as various sensors, energy conversion elements, capacitors, and the like, because ceramics have high performance, a large degree of freedom in shape, and material design is relatively easy.
The piezoelectric ceramic is obtained by subjecting a ferroelectric ceramic to so-called polarization treatment with an electric field applied thereto so as to align the polarization direction of the ferroelectric material in a fixed direction. In the piezoelectric ceramic, in order to align all spontaneous polarizations in a fixed direction by polarization treatment, an isotropic perovskite-type crystal structure having a directional orientation capability capable of spontaneous polarization in a three-dimensional space is advantageous. Therefore, most of piezoelectric ceramics that have been put into practical use are isotropic perovskite-type ferroelectric ceramics.
As the isotropic perovskite type ferroelectric ceramic, for example, lead-containing PZT (PbTiO) 3 -PbZrO 3 ) Ceramics as a basic component have been used. Piezoelectric ceramics composed of PZT have good piezoelectric properties compared with other piezoelectric ceramics. However, piezoelectric ceramics and the like composed of PZT contain lead in their constituent elements, and have a risk of precipitating toxic lead from industrial waste and the like, resulting in environmental pollution. Meanwhile, due to recent growing awareness of environmental problems, there is a tendency to avoid production of products such as PZT, which causes environmental pollution. Therefore, a piezoelectric ceramic containing no lead in chemical composition and having piezoelectric characteristics equivalent to those of PZT is required.
As for lead-free piezoelectric ceramics containing no lead, for example, baTiO 3 Are known. Containing BaTiO 3 The piezoelectric ceramic of (a) has a piezoelectric property showing a high level and is being used for sonar or the like, however, its piezoelectric property is very low as compared with PZT and its low performance is not satisfactory.
In order to improve the piezoelectric characteristics of lead-free piezoelectric ceramics, various techniques have been developed so far.
For example, japanese unexamined patent publication No. 11-180769 discloses a composition having (1-x) BNT-BaTiO 3 (wherein x = 0.06-0.12) and contains 0.5-1.5 wt% of an oxide of a rare earth element.
Japanese unexamined patent publication No. 2000-272962 discloses a compound represented by the general formula: { Bi 0.5 (Na 1-x K x ) 0.5 }TiO 3 (wherein 0.2 < x.ltoreq.0.3), and adding an additive (e.g., fe) containing 2% by weight or less of 2 O 3 、Cr 2 O 3 、MnO 2 、NiO、Nb 2 O 3 ) The obtained piezoelectric ceramic composition.
Japanese unexamined patent publication No. 2000-281443 discloses a compound represented by the general formula: xNaNbO 3 -yBaNb 2 O 6 - zBiNb 3 O 9 (wherein x + y + z =1, (x, y, z) is within a predetermined range on the three-component diagram) as a main component, and Bi is contained in a proportion of 3 to 6 wt% in terms of metal in the entire weight.
Japanese unexamined patent publication No. 2000-313664 discloses a compound represented by the general formula: k is 1-x Na x NbO 3 (wherein x =0 to 0.8) in a solid solution, and an alkali metal-containing niobium oxide-based piezoelectric ceramic composition obtained by adding 1 or more compounds selected from Cu, li and Ta.
Japanese unexamined patent publication No. 2002-137966 discloses that NaNbO has a composition formula of (1-x) 3 +xMnTiO 3 (wherein 0.014. Ltoreq. X. Ltoreq.0.08) and 0.5 to 10 mol% of KNbO based on the compound represented by the above composition formula 3 Or NaNbO 3 Piezoelectric ceramics as a subcomponent.
Japanese unexamined patent publication No. 2001-240471 discloses that Na is contained x NbO 3 (0.95. Ltoreq. X. Ltoreq.1) and a constituent represented by the formula A y BO f (A is at least 1 of K, na and Li and Bi, B is at least 1 of Li, ti, nb, ta and Sb, 0.2. Ltoreq. Y. Ltoreq.1.5, f is arbitrary), and 0.01 to 3% by weight in terms of oxide of at least 1 of a first transition metal element selected from Sc of atomic number 21 to Zn of atomic number 30, wherein the content of the subcomponent is 8 mol% or less.
Japanese unexamined patent publication No. 2003-300776 discloses a method for producing a piezoelectric ceramic composed of a perovskite-type oxide containing Nb and Ta and a tungsten bronze-type oxide containing Na, K and Li as first elements and a second element.
Japanese unexamined patent publication No. 2003-306379 discloses a perovskite-type oxide (Na) containing 1-x-y K x Li y )(Nb 1-Z Ta z )O 3 And a pyrochlore oxide M 2 (Nb 1-w Ta w ) 2 O 7 (wherein M is an element belonging to group 2 in the longitudinal direction of the periodic table).
Japanese unexamined patent publication No. 2003-327472 discloses a perovskite-type oxide (Na) -containing oxide 1-x-y K x Li y )(Nb 1-z Ta z )O 3 (wherein x is 0.1-0.9 and y is 0-0.2) and a tungsten bronze type oxide M (Nb 1-v Ta v ) 2 O 6 (wherein M is an element belonging to group 2 in the longitudinal direction of the periodic Table of the elements).
Japanese unexamined patent publication No. 2003-342069 discloses a compound represented by the formula: { Li x (K 1-y Na y ) 1-x }(Nb 1-zSb z )O 3 Wherein x, y and z are 0. Ltoreq. X.ltoreq.0.2, 0. Ltoreq. Y.ltoreq.1.0 and 0. Ltoreq. Z.ltoreq.0.2 (provided that x = z = 0) are used.
Japanese unexamined patent publication No. 2003-342071 discloses a compound represented by the formula: { Li x (K 1-y Na y ) 1-x }(Nb 1-z-n Ta z (Mn 0.5 W 0.5 ) n )O 3 Wherein x, y, z and n are 0. Ltoreq. X.ltoreq.0.2, 0. Ltoreq. Y.ltoreq.1.0, 0. Ltoreq. Z.ltoreq.0.4, and 0. Ltoreq. N.ltoreq.0.1.
Further, japanese unexamined patent publication 2004-7406 discloses a piezoelectric element comprising a piezoelectric ceramic containing ceramic crystal grains having anisotropy and spontaneous polarization, which are preferentially oriented to one plane.
As described in 11 patent documents, it is known that sinterability and piezoelectric characteristics are enhanced when various additives are added to a lead-free ferroelectric matrix. However, it is not satisfactory to improve the piezoelectric characteristics only by adding additives, for the reasons described below. That is, when an isotropic perovskite-type compound is produced according to a conventional ceramic production method, that is, when a simple compound containing each component is used as a starting material and firing, molding and calcining are performed, the orientation of each crystal grain in the resulting sintered body is random. Therefore, even in the case where the composition itself has high piezoelectric characteristics or the like, the sintered body obtained in practice may be unsatisfactory in low voltage characteristics or the like.
Generally, it is known that the piezoelectric properties and the like of isotropic perovskite compounds differ depending on the direction of the crystal axis. Therefore, when the crystal axis for obtaining high piezoelectric characteristics or the like can be oriented in a single fixed direction, anisotropy of piezoelectric characteristics or the like can be utilized to the maximum extent, which can be expected to improve the characteristics of piezoelectric ceramics. In fact, some of the known single crystals including a lead-free ferroelectric material exhibit excellent piezoelectric characteristics and the like.
However, the single crystal has a problem of high manufacturing cost. Further, in the case where a single crystal of a solid solution contains a complex component, the component is liable to be deviated in the production of the single crystal, and the produced single crystal is not suitable for use as a practical product. Furthermore, single crystals lack fracture toughness and cannot be used under high stress conditions, and thus the range of use thereof is limited.
On the other hand, according to the method of orienting a particular crystal plane using a plate-like powder having a predetermined composition as a reactive template, as disclosed in japanese unexamined patent publication No. 2004-7406, a grain-oriented ceramic in which a specific crystal plane is oriented at a high degree of orientation can be easily and inexpensively produced.
However, if Ba is used 6 Ti 17 O 40 、Bi 4 Ti 4 O 12 The plate-like powder having such a constitution is used as a reactive template, and the crystal grain-oriented ceramic obtained is one in which the a-site element (Ba or Bi) and the B-site element (Ti) contained in the plate-like powder are surely left. Therefore, when the method is applied to a goethite-type potassium sodium niobate or a solid solution thereof which exhibits isotropy of relatively high piezoelectric characteristics even in a non-lead system, it may not be possible to achieve the method in some casesIn the most preferable composition, the piezoelectric characteristics may be impaired because the a-site element and/or the B-site element are inevitably contained.
Therefore, the conventional piezoelectric material still has unsatisfactory low-voltage characteristics as compared with a piezoelectric material containing lead such as PZT, and more improvement is required.
[ summary of the invention ]
The present invention has been made in view of these problems, and an object of the present invention is to provide a grain-oriented ceramic capable of providing excellent piezoelectric characteristics, and a method for producing the same. And to provide a piezoelectric material, a dielectric material, a thermoelectric conversion element and an ion-conducting element for use in the grain-oriented ceramics.
[ means for solving problems ]
The first invention is a grain-oriented ceramic comprising, as a main phase, a metal oxide represented by formula (1): { Li x (K 1-y Na y ) 1-x }(Nb 1-a-w Ta z Sb w )O 3 Wherein x, y, z and w are isotropic perovskite compounds represented by 0. Ltoreq. X.ltoreq.0.2, 0. Ltoreq. Y.ltoreq.1, 0. Ltoreq. Z.ltoreq.0.4, 0. Ltoreq. W.ltoreq.0.2 and x + z + w > 0,
wherein
The main phase includes a polycrystal containing 0.0001 to 0.15 mol of any one or more elements selected from the group consisting of metal elements belonging to groups 2 to 15 of the periodic table, semimetal elements, transition metal elements, noble metal elements and alkaline earth metal elements per 1 mol of the compound represented by formula (1), and the specific crystal planes of the respective crystal grains constituting the polycrystal are oriented (claim 1).
In the grain-oriented ceramic of the present invention, the following formula (1): { Li x (K 1-y Na y ) 1-x }(Nb 1-z-w Ta z Sb w )O 3 The isotropic perovskite compound represented serves as a main phase. The compound represented by formula (1) corresponds to the formula ABO 3 A compound represented by the formula, wherein the element at the A-position is K, na and/or Li and the element at the B-position is Nb, sb and/or Ta. In other words, the compound represented by formula (1) is isotropic perovskite potassium sodium niobate (KNaNbO) 3 ) Here, a certain number of a-position elements are replaced by a predetermined number of Li and a certain number of B-position elements are replaced by a predetermined number of Ta and/or Sb. Therefore, the piezoelectric ceramic component of the present invention can exhibit excellent piezoelectric characteristics as compared with piezoelectric ceramics containing no Li, ta, sb, or the like in those components.
The main phase includes a polycrystalline sintered body containing 0.0001 to 0.15 mole of any one or more elements selected from the group consisting of metal elements belonging to groups 2 to 15 of the periodic table, semimetal elements, transition metal elements, noble metal elements, and alkaline earth metal elements per 1 mole of the compound represented by formula (1).
Therefore, the grain-oriented ceramic has more excellent piezoelectric characteristics, such as piezoelectric d, than a piezoelectric ceramic having the same composition but containing no additional element as described above 31 Constant, electromechanical coupling coefficient Kp and piezoelectricityg 31 A constant.
In the above grain-oriented ceramic, the additional element may be added to the compound represented by formula (1) by substitution, or may be added from the outside and be present in the crystal grains and/or at the crystal grain interfaces of the compound represented by formula (1). Furthermore, the additional element may comprise an additional simple element or may be, for example, an oxide or a compound containing an additional element.
In the above-mentioned grain-oriented ceramics, specific crystal planes constituting respective crystal grains of the polycrystal are oriented. Therefore, the grain-oriented ceramics have more excellent piezoelectric characteristics, such as piezoelectric d, than piezoelectric ceramics having the same composition but without orientation 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 A constant.
Thus, the grain-oriented ceramic of the first invention is environmentally safe because it does not contain lead, and at the same time, can be used as a high-performance piezoelectric element because of its excellent piezoelectric characteristics.
Further, the above grain-oriented ceramics are excellent in dielectric properties such as relative dielectric constant and dielectric loss in addition to piezoelectric characteristics, and therefore, the grain-oriented ceramics can also be used as a high-performance dielectric member.
The second invention is a piezoelectric element comprising a piezoelectric material containing the grain-oriented ceramic of the first invention. Due to the high performance, the grain-oriented ceramics of the first and second invention can also be used for coating films without a sintering process (claim 12).
The piezoelectric element of the second invention comprises a piezoelectric material containing the grain-oriented ceramic of the first invention. Therefore, the piezoelectric element can use the above-mentioned characteristics of the grain-oriented ceramics having excellent piezoelectric characteristics, and therefore, can be used in a wide range such as, for example, sensors such as acceleration sensors, pyroelectric sensors, ultrasonic sensors, electric field sensors, temperature sensors and gas sensitive elements: energy conversion elements such as thermoelectric converters and piezoelectric transducers; low loss actuators and low loss resonators such as piezoelectric actuators, ultrasonic motors and resonators: capacitance: and as functional ceramic materials in ion conductors.
A third invention is a dielectric element comprising a dielectric material containing the grain-oriented ceramic of the first invention (claim 13).
The dielectric element of the third invention comprises a dielectric material comprising the grain-oriented ceramic of the first invention. Therefore, the dielectric element can utilize the above-described grain-oriented ceramic characteristics having excellent relative permittivity and dielectric loss, and thus can be used as, for example, a capacitor having a large electrostatic capacity.
A fourth invention is a thermoelectric conversion element comprising a thermoelectric conversion material containing the grain-oriented ceramic of the first invention (claim 14).
A fifth invention is an ion-conducting element comprising an ion-conducting material comprising the grain-oriented ceramic of the first invention (claim 15).
The thermoelectric conversion element of the fourth invention and the ion-conducting element of the fifth invention comprise a thermoelectric conversion material containing the grain-oriented ceramic of the first invention. Therefore, the thermoelectric conversion element and the ion-conducting element can utilize the excellent piezoelectric characteristics of the above grain-oriented ceramics, and therefore, high performance and micro-loss can be achieved.
The sixth invention is a method for producing a grain-oriented ceramic, comprising:
a mixing step of mixing (i) a first anisotropically shaped powder comprising oriented fine particles having an orientation plane in which a particular crystal plane is oriented, (ii) producing formula (1) by chemical reaction with the first anisotropically shaped powder: { Li x (K 1-y Na y ) 1-x }(Nb 1-z-w Ta z Sb w )O 3 (wherein 0. Ltoreq. X.ltoreq.0.2, 0. Ltoreq. Y.ltoreq.1, 0. Ltoreq. Z.ltoreq.0.4, 0. Ltoreq. W.ltoreq.0.2 and x + z + w > 0), and (iii) any one or more additional elements selected from the group consisting of metal elements belonging to groups 2 to 15 of the periodic Table of the elements, semimetal elements, transition metal elements, noble metal elements and alkaline earth metal elements, thereby producing a raw material mixture,
a molding step of molding the raw material mixture so that the orientation planes of the first anisotropically shaped powder are oriented in almost the same direction in a molded body, and
a heat treatment step of heating the molded body to react the first anisotropically shaped powder with the first reaction raw material, thereby producing a polycrystalline body which contains an isotropic perovskite-type compound represented by formula (1) and whose crystal grains are oriented and exhibit a texture structure,
wherein
In the mixing step, the additional element is added in an amount of 0.0001 to 0.15 mol per mol of the compound represented by formula (1), and
the oriented planes of the oriented fine particles have a lattice matching a particular plane among the crystal grains constituting the polycrystalline body obtained in the heat treatment step (claim 16).
The method for producing a grain-oriented ceramic of the present invention comprises the above-described mixing step, molding step and heat treatment step.
In the mixing step, the first anisotropic morphological powder, the first reaction raw material, and the additional element are mixed to produce a raw material mixture.
In the molding step, the raw material mixture obtained above is molded, and thus the particular crystal plane of the morphological powder of the first anisotropy is oriented in a specific direction in the molded body.
In the heat treatment step, the first anisotropic morphology powder and the first reaction raw material are heated and reacted to obtain the above molded body.
The oriented fine particles constituting the first anisotropic morphology powder have one orientation plane formed by orienting a specific crystal plane, and the raw material mixture is formed such that the orientation planes of the oriented fine particles are oriented in almost the same direction in the molded body. More specifically, in the molding step, the molding raw material mixed powder, for example, by allowing a force to act on the first anisotropic morphology powder from one direction, with the result that the first anisotropic morphology powder can be oriented in the molded body by the action of shear stress acting on the first anisotropic morphology powder. When the molded body is heated in the heat treatment step, the first anisotropic morphology powder and the first reaction raw material react, whereby anisotropic morphology crystals containing an isotropic perovskite-type compound aligned in the direction of orientation of the first anisotropic morphology powder can be produced, and in turn the compound represented by formula (1) can be produced on the particular crystal plane that has been oriented.
In the production method of the present invention, there is lattice matching between the orientation plane of the first anisotropic morphology powder and the particular crystal plane of the compound represented by formula (1). Therefore, the first anisotropic morphology powder functions as a template or a reaction template, and the orientation plane of the first anisotropic morphology powder coincides with the particular crystal plane of the compound represented by formula (1). Therefore, the compound represented by formula (1) can be produced as described above, with the particular crystal plane oriented in one direction.
In the heat treatment step, the compound represented by formula (1) is produced and simultaneously calcined, whereby a polycrystalline sintered body can be preferably produced. The grain-oriented ceramic can be obtained in this way.
In the mixing step, the above-mentioned additional element is added in the above-mentioned specific amount together with the planar powder and the perovskite manufacturing raw material. An additional element substituted by any one or more of Li, K, na, nb, ta and Sb is added to the isotropic perovskite-type compound represented by formula (1), or is added on the surface of the compound represented by formula (1), which is present at the grain boundary of the compound represented by formula (1).
In the thus obtained grain-oriented ceramic, the main phase is represented by formula (1): { Li x (K 1-y Na y ) 1-x }(Nb 1-z-w Ta z Sb w )O 3 (wherein x is 0. Ltoreq. X.ltoreq.0.2, y is 0. Ltoreq. Y.ltoreq.1, z is 0. Ltoreq. Z.ltoreq.0.4, w is 0. Ltoreq. W.ltoreq.0.2, and x + z + w > 0). Meanwhile, the main phase comprises a compound containing 0.0001 to 0.15 mole of any one or more of the compounds represented by the formula (1) per 1 mole of the compoundA plurality of polycrystals selected from the group consisting of metal elements belonging to groups 2 to 15 of the periodic table, semimetal elements, transition metal elements, noble metal elements and alkaline earth metal elements, and particular crystal planes of respective crystal grains constituting the polycrystals are oriented. That is, according to the sixth invention, the grain-oriented ceramic of the first invention can be obtained.
The grain-oriented ceramic obtained in the present invention contains Li, ta, and Sb each in a specific amount, and further contains the above-described additional elements. Therefore, the grain-oriented ceramics have piezoelectric characteristics (for example, piezoelectric d) in comparison with an element containing an isotropic perovskite-type compound instead of these 31 Constant, electromechanicalCoupling coefficient Kp and piezoelectric g 31 Constant) and excellent in dielectric properties. Moreover, in the grain-oriented ceramics, specific crystal planes are highly oriented. Therefore, the grain-oriented ceramic is excellent in piezoelectric characteristics and dielectric properties as compared with an isotropic piezoelectric ceramic having the same composition.
[ brief description of the drawings ]
Fig. 1 is a graph showing the X-ray diffraction results of sample E1 obtained according to the test example.
Fig. 2 is a graph showing the X-ray diffraction results of sample E2 obtained according to the test example.
Fig. 3 is a graph showing the X-ray diffraction results of sample E3 obtained according to the test example.
Fig. 4 is a graph showing the X-ray diffraction results of sample E4 obtained according to the test example.
Fig. 5 is a graph showing the X-ray diffraction results of sample E5 obtained according to the test example.
Fig. 6 is a graph showing the X-ray diffraction results of sample E6 obtained according to the test example.
Fig. 7 is a graph showing the X-ray diffraction results of sample E7 obtained according to the test example.
Fig. 8 is a graph showing the X-ray diffraction results of sample E8 obtained according to the test example.
Fig. 9 is a graph showing the X-ray diffraction results of sample E9 obtained according to the test example.
Fig. 10 is a graph showing the X-ray diffraction results of sample E10 obtained according to the test example.
Fig. 11 is a graph showing the X-ray diffraction results of sample C2 obtained according to the test example.
Fig. 12 is a graph showing the relationship between the dielectric loss tan δ and the temperature of the samples E11 and C13 according to the test example.
[ best mode for carrying out the invention ]
Embodiments of the present invention are described below.
The grain-oriented ceramic comprises a ceramic having the formula (1): { Li x (k 1-y Na y ) 1-x }(Na 1-z-w Ta z Sb w )O 3 Wherein x, y, z and w are 0-0.2, 0-1, 0-0.4, 0-0.2 and x + z + w 0.
The grain-oriented ceramic has a grain-oriented structure comprising potassium sodium niobate (K) 1-y Na y )NbO 3 Is one of isotropic perovskite compounds, where a part of the a-site elements (K and Na) is replaced by a predetermined amount of Li and/or a part of the B-site elements (Nb) is replaced by a predetermined amount of Ta and/or Sb.
In formula (1): { Li x (K 1-y Na y ) 1-x }(Nb 1-z-w Ta z Sb w )O 3 Piezoelectric properties (e.g. piezoelectric d) if x > 0.2, z > 0.4, w > 0.2, or for x + z + w =0 31 Constant) and dielectric characteristics are lowered, and grain-oriented ceramics having satisfactory characteristics cannot be obtained.
In the formula (1), x + z + w > 0 means that it is sufficient if at least one element of Li, ta and Sb is contained in the substitution element.
As described above, the grain-oriented ceramic has a structure comprising perovskite (ABO) 3 ) The main phase of the compound. In the present invention, in the perovskite structure (ABO) 3 ) The A-site elements of (A) are K, na and Li, and the B-site elements are Nb, ta and Sb, respectively. In the compositional formula of the perovskite structure, when the stoichiometric ratio of atoms constituting the elements at the A site to atoms constituting the B site is 1: 1, the complete perovskite structure is formed. However, in the above grain-oriented ceramics, in particular, K, na, li and Sb may volatilize by several percent, specifically, by about 3% due to heating or the like during the production, or all the constituent elements may change by several percent, specifically, by about 3% due to mixing/grinding, granulation or the like during the production. That is, deviations in the stoichiometry of the chemical components may occur due to fluctuations in the production process.
In order to cope with the fluctuation of the composition during the production, the mixing of the components may be intentionally changed so that the composition ratio of the grain-oriented ceramics after the heat treatment (firing) may be changed within plus or minus a few percent, specifically, at a level of + -3-5%. The same applies to the case of conventional ceramics, such as zirconium titanate (PZT), the mixing ratio of which can be modified by taking into account the volatilization of lead during firing or during mixing of zirconia in the grinding media zirconia beads.
In the above grain-oriented ceramics, even if the mixed component ratio is intentionally changed to the above value, the electrical characteristics such as piezoelectric characteristics are not greatly changed.
Thus, in the present invention, formula (1): { Li x (K 1-y Na y ) 1-x }(Nb 1-z-w Ta z Sb w )O 3 The compound may have a compositional ratio such that when the compound is used in the perovskite structure component formula ABO 3 The deviation of the A site element and the B site element from the composition ratio of 1: 1 was about. + -. 5 mol%. Sometimes, in order to reduce lattice defects in the crystal structure and obtain high electrical characteristics, it is preferable that the composition is deviated at mostAbout. + -. 3%.
That is, the compound represented by the formula (1) includes [ Li ] as a main phase of the grain-oriented ceramic x (K 1-y Na y ) 1-x ] a {(Nb 1-z-w Ta z Sb w )} b O 3 (wherein x is more than or equal to 0 and less than or equal to 0.2, y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 0.4, w is more than or equal to 0 and less than or equal to 0.2, x + z + w is more than or equal to 0, a is more than or equal to 0.95 and less than or equal to 1.05, and b is more than or equal to 0.95 and less than or equal to 1.05). Also, as described above, a and b are preferably 0.97. Ltoreq. A.ltoreq.1.03 and 0.97. Ltoreq. B.ltoreq.1.03.
In formula (1), x is preferably 0 < x.ltoreq.0.2.
In this case, the compound represented by formula (1) contains Li as an essential component, and therefore, the grain-oriented ceramic can be fired more easily during the manufacturing process, and can have more enhanced piezoelectric characteristics and a higher curie temperature (Tc). This is that in the above-mentioned range of x, when Li is contained as an essential component, the firing temperature is lowered and at the same time, li can contribute to firing, with the result that firing is completed with less fine pores.
Meanwhile, in formula (1), x may be x =0.
In this case, formula (1) consists of (K) 1-y Na y )(Nb 1-z-w Ta z Sb w )O 3 Represented by the fact that it contains the lightest molecular weight of Li such as LiCO 3 The compound (2) is not contained in the raw materials for producing the grain-oriented ceramics, and when the grain-oriented ceramics are produced by mixing the raw materials, fluctuation in characteristics due to segregation of the raw material powders can be reduced.
In formula (1), y is preferably 0 < y.ltoreq.1.
In this case, the compound represented by formula (1) contains Na as an essential component, and therefore, the piezoelectric g of the grain-oriented ceramic can be further improved 31 And (4) constant.
Meanwhile, in the formula (1), y may be 0. Ltoreq. Y < 1.
In this case, the compound represented by the formula (1) contains K as an essential component, and therefore, mayTo further improve the piezoelectric d of the grain-oriented ceramics 31 And (4) constant. Further, in this case, increasing the amount of K added allows the calcination to be carried out at a lower temperature, which makes it possible to produce grain-oriented ceramics in an energy-saving manner and inexpensively.
In formula (1), y may be y =0.
In this case, formula (1) consists of (Li) x Na 1-x )(Nb 1-z-w Ta z Sb w )O 3 As represented, since the compound represented by formula (1) does not contain Na, the grain-oriented ceramic can be improved in view of dielectric loss.
Meanwhile, in formula (1), y may be y =1.
In this case, formula (1) consists of (Li) x k 1-x )(Nb 1-z-w Ta z Sb w )O 3 Because the compound represented by the formula (1) does not contain K, K 2 CO 3 And the like are not necessary as raw materials for producing the compound due to solubility. Further, since the K component is easily sublimated and lost without being contained during the heat treatment, it is possible to facilitate the treatment for the synthesis of the raw material and the adjustment of the compound component.
In formula (1): { Li x (K 1-y Na y ) 1-x )(Nb 1-z-w Ta z Sb w )O 3 Y is more preferably 0.05. Ltoreq. Y.ltoreq.0.75, and still more preferably 0.20. Ltoreq. Y.ltoreq.0.70. In this case, the piezoelectric d can be further increased 31 A constant and an electromechanical coupling coefficient Kp. Further, it is preferably 0.20. Ltoreq. Y < 0.70, more preferably 0.35. Ltoreq. Y < 0.65, still more preferably 0.35. Ltoreq. Y < 0.65, most preferably 0.42. Ltoreq. Y < 0.60.
In formula (1), z is preferably 0 < z.ltoreq.0.4.
In this case, the compound represented by formula (1) contains Ta as an essential component, and therefore, the temperature of firing is lowered while Ta acts as a firing aid, with the result that pores in the grain-oriented ceramic are reduced.
In formula (1), z may be z =0.
In this case, formula (1) is represented by { Li x (K 1-y Na y ) 1-x )(Nb 1-w Sb w )O 3 Is represented by the formula (1)The compound represented by formula (1) does not contain Ta, and an excellent piezoelectric constant can be obtained without using expensive Ta.
Meanwhile, in the formula (1), w is preferably 0 < w.ltoreq.0.2.
In this case, the compound represented by formula (1) contains Sb as an essential component, and therefore, the sintering temperature is lowered, with the result that sinterability and stability of dielectric loss tan δ can be improved.
In formula (1), w may be w =0.
In this case, formula (1) is represented by { Li [ ] x (K 1-y Na y ) 1-x )(Nb 1-z Ta z )O 3 The compound represented by formula (1) may exhibit a relatively high curie temperature because the compound does not contain Sb.
In the above grain-oriented ceramic, the main phase is an isotropic perovskite-type compound represented by formula (1). The term "main phase" as used herein refers to a compound represented by formula (1) occupying a ratio of 90% by volume or more in the entire grain-oriented ceramic. As for the remaining less than 10 vol% of the component, other phases may be contained as long as the isotropic perovskite-type crystal structure can be maintained and individual characteristics such as sintering characteristics and piezoelectric characteristics are not adversely affected. Examples of "other phases" include additives, calcination aids, by-products and impurities (e.g., bi) 2 O 3 、CuO、MnO 2 NiO) produced from the production method described below or the raw materials used.
The main phase includes a polycrystal containing 0.0001 to 0.15 mol of any one or more elements selected from the group consisting of metal elements belonging to groups 2 to 15 of the periodic table, semimetal elements, transition metal elements, noble metal elements and alkaline earth metal elements per mol of the compound represented by formula (1).
If the content of the additional element is less than 0.0001 mol or exceeds 0.15 mol, the piezoelectric characteristics or dielectric characteristics of the grain-oriented ceramic may be degraded.
The content of the additional element is preferably 0.0001 to 0.05 mol, more preferably 0.0001 to 0.02 mol, and further preferably 0.0005 to 0.02 mol per mol of the compound represented by the formula (1).
The additional element may take the form of, by substituting equation (1): { Li x (K 1-y Na y ) 1-x }(Nb 1-z-w Ta z Sb w )O 3 At least a part of Li, K, na, nb, ta and Sb in the represented compound align the additional elements. For example, elements capable of becoming +2 valent such as Mg, ca, sr and Ba may be arranged to replace at least a part of Li, K and Na of the compound represented by formula (1). Elements capable of becoming +1 or +2 valent, such as Cu, ni, fe and Zn, may also be arranged to replace at least a part of Li, K and Na of the compound represented by formula (1). On the other hand, elements capable of becoming +3 to +6 valent, such as Fe and Mn, tend to be arranged to replace at least a part of Na, ta and Sb in the compound represented by the above formula. In this way, the additional elements take the form of substitutional solid solutions in the grain-oriented ceramic, which can be increased even moreCharacteristics such as piezo-electric d 31 And (4) constant.
The additional element may also take the form of a single element or an oxide or compound (e.g., perovskite-type compound) containing additional elements present at the grains or grain boundaries of the grain-oriented ceramic.
The additional element is preferably contained in the crystal grains constituting the polycrystalline body and/or in the grain boundaries (claim 2). That is, the additional element is preferably externally added to the compound represented by formula (1).
In this case, the additional element can be easily and simply added to the compound represented by formula (1). Further, by precipitating another single element or compound containing an additional element in the crystal grains or on the crystal grain boundary, a dispersion strengthening effect is exerted and the strength or toughness of the ceramic can be improved.
The addition ratio of the additional element is preferably 0.01 to 15 atomic% (atm%) by replacing any one or more selected from Li, K, na, nb, ta, and Sb in the isotropic perovskite-type compound represented by formula (1) (claim 3).
In this case, the piezoelectric characteristics (e.g., piezoelectric d) of the grain-oriented ceramic can be more improved 31 Constant, electromechanical coupling coefficient Kp) and dielectric characteristics (e.g., relative dielectric constant ε) 33T /ε 0 )。
If the content of the additional element is less than 0.01 atomic% or exceeds 15 atomic%, the piezoelectric characteristics or dielectric properties of the grain-oriented ceramics can be lowered.
The content of the additional element is preferably 0.01 to 5 atom%, more preferably 0.01 to 2 atom%, further preferably 0.05 to 2 atom%, based on any one or more selected from Li, K, na, nb, ta and Sb in the isotropic perovskite-type compound represented by formula (1).
As used herein, "atomic%" means the percentage ratio of the number of replacing atoms to the total number of atoms of Li, K, na, nb, ta and Sb in the compound represented by formula (1).
The additional element is preferably any one or more elements selected from the group consisting of Mg, ca, sr and Ba (claim 4).
In this case, the additional member may easily replace at least a part of K and/or Na in the compound represented by formula (1), and thus, the compound represented by formula (1) may be a compound represented by formula (3): { Li x (K 1-y Na y ) 1-x-2u Ma u }(Nb 1-z-w Ta z Sb w )O 3 (wherein Ma is at least one or more metal elements selected from the group consisting of Mg, ca, sr and Ba, and x, y, z, w and u are 0. Ltoreq. X.ltoreq.0.2, 0. Ltoreq. Y.ltoreq.1, 0. Ltoreq. Z.ltoreq.0.4, 0. Ltoreq. W.ltoreq.0.2, x + z + w > 0, and 0.0001. Ltoreq. U.ltoreq.0.15), as a result of which the piezoelectric characteristics of the grain-oriented ceramic (for example, piezoelectric d) can be more improved 31 Constant, electromechanical coupling coefficient Kp) and dielectric properties: (E.g. relative dielectric constant ε 33T /ε 0 )。
Meanwhile, the additional element is preferably any one or more elements selected from Sc, ti, V, cr, mn, fe, co, ni, cu, zn, Y, zr, mo, hf, W and Re (claim 5).
In this case, the piezoelectric characteristics such as mechanical quality factor Qm, piezoelectric d of the grain-oriented ceramic can be more improved 31 Constant and dielectric loss tan δ.
The additional element is preferably any one or more elements selected from the group consisting of Pd, ag, ru, rh, pt, au, ir and Os (claim 6).
In this case, the piezoelectric characteristics (e.g., piezoelectric d) of the grain-oriented ceramics can be more improved 31 Constant, e.g. piezoelectric g 31 Constant, electromechanical coupling constant Kp) and dielectric properties (e.g. relative dielectric constant ε) 33T /ε 0 Dielectric loss tan δ).
Meanwhile, the additional element is preferably any one or more elements selected from the group consisting of B, al, ga, in, si, ge, sn and Bi (claim 7).
In this case, the additional element acts as a calcination aid and promotes densification of the grain-oriented ceramic, and therefore, the grain-oriented ceramic can be easily calcined. As a result, the grain-oriented ceramics have good qualities such as high apparent density and less fine pores and in turn ensure excellent mechanical strength.
In the grain-oriented ceramic, a specific crystal plane of each crystal grain constituting the above polycrystal is oriented.
The term "the specific crystal planes are oriented" means that the respective crystal grains are arranged so that the specific crystal planes of the compound represented by the formula (1) are parallel to each other (hereinafter, this state is referred to as "plane orientation") or the respective crystal grains are oriented so that the specific crystal planes are parallel to one axis running through the molded body (hereinafter, this state is referred to as "axis orientation").
The kind of oriented crystal plane is not particularly limited, and is selected according to the direction in which the compound represented by formula (1) spontaneously polarizes, the use of the grain-oriented ceramic, the required characteristics, and the like. That is, the oriented crystal plane is selected from pseudo-cubic {100} plane, pseudo-cubic {110} plane, pseudo-cubic {111} plane, and the like, according to the purpose.
"pseudo-cubic { HKL }" refers to a structure that is regarded as cubic and represented by miller indices because deformation thereof is small although an isotropic perovskite-type compound generally has a structure in which cubic crystals such as tetragonal crystals, orthorhombic crystals, or trigonal crystals are slightly deformed.
In the case where the specific crystal plane is in a plane orientation, the degree of plane orientation, which is an average degree of orientation F (HKL) measured according to the Lotgering method, can be represented by the following mathematical formula 1:
(mathematical formula 1)
In the mathematical formula 1, Σ I (hkl) is the sum of the X-ray diffraction intensities of all crystal planes (hkl) measured for grain-oriented ceramics, Σ I 0 (hkl) is the sum of the X-ray diffraction intensities of all crystal planes (hkl) measured for a non-oriented ceramic having the same composition as the grain-oriented ceramic. Moreover, Σ 'I (HKL) is the sum of the X-ray diffraction intensities of the crystallographically equivalent specific crystal planes (HKL) measured for grain-oriented ceramics, Σ' I o (HKL) is the sum of the X-ray diffraction intensities of the crystallographically equivalent specific crystal planes (HKL) measured for a non-oriented ceramic having the same composition as the grain-oriented ceramic.
Therefore, when each crystal grain constituting the polycrystalline body is non-oriented, the average degree of orientation F (HKL) is 0%. Further, when the (HKL) planes of all the crystal grains constituting the polycrystalline body were oriented parallel to the measurement plane, the average degree of orientation F (HKL) was 100%.
In the grain-oriented ceramics, high characteristics are obtained as the proportion of oriented crystal grains increases. For example, when a particular crystal plane is oriented, in order to obtain high piezoelectric characteristics or the like, it is preferable that the average degree of orientation F (HKL) measured by the Lotgering method represented by the following mathematical formula 1 is 30% or more (claim 8). The average degree of orientation is more preferably 50% or more. The specific crystal plane to be oriented is preferably a plane perpendicular to the polarization axis. When the crystal system of the perovskite compound is tetragonal, the specific crystal plane to be oriented is preferably a {100} plane.
When a specific crystal plane is axially oriented, the degree of orientation cannot be defined by the same degree of orientation (formula 1) as the plane orientation, but when X-ray diffraction is performed on a plane perpendicular to the orientation axis, the degree of axial orientation represented by the average degree of orientation (hereinafter referred to as "degree of axial orientation") can be measured by the Lotgering method associated with (HKL) diffraction. The degree of axial orientation of the molded article in which the specific crystal plane is substantially completely axially oriented is substantially the same as the degree of axial orientation measured for the molded article in which the specific crystal plane is substantially completely plane oriented.
Grain-oriented ceramic piezoelectric d 31 The constant is preferably 1.1 times or more as large as that of a non-oriented ceramic having a polycrystalline body of the same composition as that of a grain-oriented ceramic, and in which crystal planes constituting the grains of the polycrystalline body are not oriented or are not oriented in such a manner that the grains exhibit a textured structure (claim 9).
The grain-oriented ceramic has an organic electric coupling coefficient Kp preferably 1.1 times or more that of a non-oriented ceramic having the same composition as that of a grain-oriented ceramic, and in which crystal planes constituting crystal grains of a polycrystalline body are not oriented or crystal grains show an orientation of a textured structure (claim 10).
Grain oriented ceramic piezoelectric g 31 The constant is preferably 1.1 times or more as large as that of a non-oriented ceramic having the same composition polycrystal as the grain-oriented ceramic, and in which the crystal planes constituting the crystal grains of the polycrystal have no orientation or no orientation in which the crystal grains exhibit a textured structure (claim 11).
Piezoelectric g of grain-oriented ceramics 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 Each constant is1.1 times or more the non-oriented ceramic, it is possibleThe effect obtained by the particular crystal plane orientation is fully exerted. Therefore, in this case, it is convenient to use piezoelectric elements such as a piezoelectric actuator, a piezoelectric filter, a piezoelectric oscillator, a piezoelectric sensor, a piezoelectric ultrasonic motor, a piezoelectric gyro sensor, a knock sensor (knock sensor), a yaw rate sensor, an air bag sensor, a back sonar, a corner sonar, a piezoelectric buzzer, a piezoelectric speaker, and a piezoelectric combustion device.
In the grain-oriented ceramic of the present invention, the piezoelectric d is obtained by optimizing the chemical composition, the degree of orientation, the production conditions, and the like of the compound represented by formula (1) 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 The constants are each 1.1 times or more that of the non-oriented ceramic. By carrying out further optimization, the piezoelectric d can be made 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 The constants are each 1.2 times or more, or 1.3 times or more.
The driver material utilizes displacement generated in a direction parallel to the direction of applied voltage under a large electric field having an electric field strength of 100V/mm or more. In using the above grain-oriented ceramic as a material for actuators, by optimizing the composition, degree of orientation, production conditions, and the like of the compound represented by formula (1) constituting the main phase thereof, the grain-oriented ceramic is obtained which produces a displacement of 1.1 times or more as large as that of a non-oriented sintered body having the same composition under a large electric field under the same temperature and the same electric field strength condition. By optimizing these conditions, the grain-oriented ceramics produced have a displacement of 1.2 times or more that of the non-oriented sintered body having the same composition, and if these conditions are still further optimized, the displacement may be 1.3 times or more.
Meanwhile, the material for the driver is required to have small temperature dependence of displacement that needs to be generated under a large electric field. The non-oriented ceramic has a large temperature dependence on displacement, and is not suitable for actuator applications. On the other hand, in the grain-oriented ceramic of the present invention, by optimizing the composition, the degree of orientation, the production conditions, and the like of the compound represented by the above formula constituting the main phase thereof, the obtained grain-oriented ceramic has excellent temperature characteristics in which the maximum value and the minimum value of the displacement generated under a large electric field are within at least ± 20% of the entire temperature range of 100 ℃ or more arbitrarily. Further, these conditions are optimized, and the maximum displacement and the minimum displacement of the obtained grain-oriented ceramic in any temperature range of 100 ℃ or more are within at least 10% of the average value, and if further optimized, within 7%, and if further optimized, within 5%. In some cases, in order to increase the displacement amount, the electric field intensity during driving is preferably 500V/mm or more, more preferably 1000V/mm or more.
The methods of controlling the displacement generated under a large electric field may be classified into (a) a voltage control method of controlling the displacement using a voltage as a parameter, (b) an energy control method of controlling the displacement using an injection energy as a parameter, and (c) a charge control method of controlling the displacement using an injected charge as a parameter.
In the case of the voltage control method (a), the temperature dependence of displacement generated at a constant voltage is preferably small.
In the case of the energy control method (b), the temperature dependence of displacement generated at a constant implantation energy is preferably small.
In the case of the charge control method (c), the temperature dependence of displacement occurring with a constant injected charge is preferably small.
In the case of energy control and charge control, the terminal voltage applied to the driver and the drive circuit fluctuates due to the temperature dependence of the capacitance in a large electric field, and therefore the circuit must be designed with an upper limit of the fluctuation range of the terminal voltage. Since a high withstand voltage and a high-priced circuit element are sometimes required due to the temperature dependence of the capacitance, the temperature characteristic of the capacitance is preferably small. The above can be easily understood from the following formulae A3 and A4.
W＝1/2×C×V 2 A3
Q＝C×V A4
Here, W: energy (J), C: capacitance (F), V: applied voltage (V) and Q: a charge (C).
In addition, since the displacement of the actuator (electric field induced displacement amount: Δ L) is in a proportional relationship with the applied voltage, the displacement in constant electric field drive (EF: constant) and D are 331arge In proportion, as can be understood from the following formula A5,
ΔL＝D 331arge ×EF max ×L A5
here, D 331arge : dynamic deformation (m/V), EF max : maximum electric field strength (V/m) and L: the original length (m) before voltage application. D 331arge When the device is driven by applying a high voltage having an electric field intensity of 0 to 2,000V/mm at a constant amplitude, the displacement generated in the direction parallel to the applied voltage, which is determined from the formula A6, is defined as the dynamic deformation:
D 331arge ＝S max /EF max ＝(ΔL/L)/(V/L) A6
the displacement (. DELTA.L) in low energy driving (W: constant) is represented by the following formulae A7 and A8
Is represented by, and D 331arge /(E 331arge ) 1/2 In proportion:
ΔL＝D 331arge ×(2×W/C) 1/2 A7
C＝E 331arge ×ε 0 ×A/L A8
here, Δ L: electric field induced displacement (m), E 331arge : dynamic dielectric constant, a: electrode area (m) 2 ) And epsilon 0 : dielectric constant (F/m) in vacuum.
E 331arge And (4) measuring. Is carried out at a high voltage with a constant-amplitude applied electric field intensity of 0-2000V/mmIn the case of driving, the amount of polarization obtained from the polarization amount-hysteresis loop is measured according to formula A9, and based on this, the amount of injected charge driven under a high electric field is calculated as a relative permittivity (dynamic permittivity).
E 331arge ＝P max /(EF max ×ε 0 )＝(Q max /A)/((V/L×ε 0 ) A9
Here, P max : maximum charge density (C/m) 2 ) And Q max : maximum charge (C).
In addition, the displacement (electric field induced displacement amount: Δ L) in the constant charge driving (Q: constant)
As represented by the formulae A10 and A8, with D 331arge /E 331arge In proportion:
ΔL＝D 331arge ×Q/C A10
for the non-oriented sintered body, due to D 331arge And E 331arge Has a large temperature dependence of D 331arge /(E 331arge ) 1/2 And D 331arge /E 331arge Is also highly temperature dependent, and is therefore unsuitable for use as a driver.
On the other hand, in the grain-oriented ceramic of the present invention, by optimizing the composition, degree of orientation, production conditions and the like of the compound represented by formula (1) constituting the main phase thereof, the obtained grain-oriented ceramic has excellent temperature characteristics, and D generated under a large electric field is generated 33arge /(E 331arge ) 1/2 、D 331arge /E 331arge And E 331arge Is within at least + -20% of the range of variation of the maximum value and the minimum value of (a) with respect to the average value over any temperature range of 100 ℃ or more.
If these conditions are further optimized, the maximum displacement and the minimum displacement of the obtained grain-oriented ceramic are within. + -. 15% from the average value in an arbitrary temperature range of 100 ℃ or more. If further optimized, within + -10%, if further optimized, within 8%, if further optimized, within 5%.
Ceramics of the compound represented by formula (1) have a complicated chemical composition, and are generally produced by the following method: the simple compounds containing the component elements are mixed to achieve a stoichiometric ratio, the resulting mixture is shaped, calcined, ground, then shaped, and sintered. However, it is extremely difficult to obtain an oriented ceramic in which a specific crystal plane of each crystal grain is oriented in a specific direction by this method.
As described above, in the sixth invention, the specific condition which the first anisotropically shaped powder satisfies is that the compound represented by the formula (1) is synthesized and sintered in the molded body using the first anisotropically shaped powder as a template or a reactive template so that the particular crystal planes of the respective crystal grains constituting the polycrystal are oriented in one direction (claim 16).
The first anisotropically shaped powder is described below.
The first anisotropically shaped powder includes oriented particles (aligned particles) having an oriented plane, where a specific crystal plane is oriented (or an oriented plane (aligned plane) formed by a specific crystal plane).
The oriented fine particles (aligned fine particles) preferably have a shape that promotes orientation in a certain direction in a molding step described later. For this reason, the oriented fine particles (aligned fine particles) preferably have an average aspect ratio (aspect ratio) of 3 or more. If the average aspect ratio is less than 3, it is difficult to orient the first anisotropically shaped powder in one direction in the shaping step described later. In order to obtain a grain-oriented ceramic having a high degree of orientation, the average aspect ratio of the first anisotropically shaped powder is preferably 5 or more. The average aspect ratio is the average of the largest dimension and the smallest dimension of the oriented particles.
The oriented particles are more easily oriented in the molding step described later when the average aspect ratio of the oriented particles is larger. However, if the average aspect ratio is too large, the oriented fine particles may be broken in a mixing step described later, and a molded body in which the oriented fine particles are oriented may not be obtained in a molding step. Therefore, the average aspect ratio of the oriented fine particles is preferably 100 or less.
The average particle diameter (average value of the longitudinal dimension) of the oriented fine particles is preferably 0.05 μm or more. If the average particle diameter of the oriented fine particles is less than 0.05. Mu.m, it becomes difficult to orient the first anisotropically shaped powder in a certain direction by, for example, shear stress acting at the time of molding. In addition, epitaxial growth to the template particles is less likely to occur when used as a reactive template in the production of grain-oriented ceramics due to the reduced benefit of interfacial energy.
The average particle diameter of the oriented fine particles is preferably 20 μm or less. If the average particle diameter of the oriented fine particles exceeds 20 μm, the sinterability is lowered, and a grain-oriented ceramic having a sintered body density cannot be obtained.
The average particle diameter of the oriented fine particles is more preferably 0.1 μm to 10 μm.
The oriented planes of the oriented fine particles have a lattice matching with a certain oriented plane oriented in the crystal grains constituting the polycrystal obtained in the heat treatment step.
The oriented grains cannot act as a reaction template for making grain oriented ceramics if the oriented planes do not have a lattice matching the lattice of one of the oriented planes oriented in the grains.
In the alignment particles, the alignment planes preferably occupy the largest area among the alignment particles.
In this case, the oriented fine particles can serve as an excellent reaction template for producing grain-oriented ceramics.
Whether the lattice matching is good or not can be represented by a value obtained by dividing the lattice size of the orientation plane of the oriented fine particles by the absolute value of the difference between the lattice size of the orientation plane of the oriented fine particles and the lattice size of the specific crystal plane of the compound represented by formula (1) (hereinafter, this value is referred to as "lattice matching ratio"), and this lattice matching ratio may be slightly different depending on the orientation of the crystal lattice to be taken. Generally, the smaller the average lattice matching ratio (average of lattice matching ratios calculated for each direction), the more the oriented fine particles can function as a good template. In order to obtain a grain-oriented ceramic having a high degree of orientation, the average lattice matching ratio of the oriented fine particles is preferably 20% or less, more preferably 10% or less.
The oriented fine particles are not necessarily the same composition as the compound represented by formula (1), and may be a substance that reacts with a first reaction raw material described later to produce a compound represented by formula (1) having a desired composition. Thus, the oriented fine particles may be selected from compounds or solid solutions containing any one or more of the cationic elements contained in the compound represented by formula (1) to be produced.
As used herein, "anisotropic forming" means that the dimension in the longitudinal direction is larger than the dimension in the width direction or the thickness direction. Examples of particularly preferable shapes include plate-like, columnar, scaly, and needle-like shapes. The type of crystal plane constituting the orientation plane is not particularly limited, and may be selected from various crystal planes according to the purpose.
If the above conditions are satisfied in the first anisotropic shaped powder comprising oriented fine particles, for example, those comprising a compound represented by the formula (2) are a perovskite-type compound such as NaNbO 3 (hereinafter, this will be referred to as "NN") and KNbO 3 (hereinafter, this is referred to as "KN"), or K 1-y Na y NbO 3 (0 < y < 1), or a compound obtained by substituting and dissolving Li, ta and/or Sb in these compounds in a predetermined amount which may be used.
{Li x (K 1-y Na y ) 1-x }(Nb 1-z-w Ta z Sb w )O 3 (2)
(wherein x, y, z and w are 0. Ltoreq. X.ltoreq.1, 0. Ltoreq. Y.ltoreq.1, 0. Ltoreq. Z.ltoreq.1 and 0. Ltoreq. W.ltoreq.1).
The compound represented by the formula (2) has, of course, good lattice matching with the compound represented by the formula (1). Therefore, oriented fine particles (hereinafter, referred to as "anisotropically shaped powder a" in particular) composed of the compound represented by formula (2) and having a specific crystal plane as an orientation plane can function as a reactive template for producing grain-oriented ceramics. In addition, since the anisotropically shaped powder a is substantially composed of the cationic element contained in the compound represented by formula (1), it is possible to produce a grain-oriented ceramic containing very little impurity element. Among these particles, oriented fine particles composed of a compound represented by formula (2) having a pseudo-cubic {100} plane as an orientation plane are preferable, and NN or KN plate-like powder having a pseudo-cubic {100} plane as an orientation plane is particularly preferable.
The first anisotropically molded powder is preferably an anisotropically molded powder which is composed of a layered perovskite compound and has a crystal plane with a small surface energy lattice-matched to a specific crystal plane of the compound represented by the formula (1). Since the crystal lattice of the layered perovskite compound has a large anisotropy, it is possible to relatively easily synthesize an anisotropically molded powder having a crystal plane with a small surface energy as an orientation plane (hereinafter, this is referred to as "2 nd anisotropically molded powder").
A first example of the layered perovskite compound suitable as a material of the 2 nd anisotropically shaped powder includes a bismuth layered perovskite compound represented by formula (4).
(Bi 2 O 2 ) 2+ (Bi 0.5 AM m-1.5 Nb m O 3m+1 ) 2- (4)
Wherein m is an integer of 2 or more, and AM is at least one alkali metal element selected from Li, K and Na.
Since the surface energy of the {001} plane of the compound represented by the formula (4) is smaller than that of the other crystal planes, the 2 nd anisotropically molded powder having the {001} plane as an orientation plane can be easily synthesized by using the compound represented by the formula (4). The "{001} plane" used herein means a plane which is in contact with a bismuth-layered perovskite compound (Bi) 2 O 2 ) 2+ The parallel faces of the layers. Also, the {001} plane of the compound represented by formula (4) and the pseudo-cubic {100} plane of the compound represented by formula (1) have excellent lattice matching.
Therefore, the 2 nd anisotropically shaped powder composed of the compound represented by the formula (4) and having the {001} plane as an orientation plane is suitable as a reactive template for producing a grain-oriented ceramic having the {100} plane as an orientation plane. Further, by optimizing the composition of the first reaction raw material described later, if the compound represented by formula (4) is used, it is possible to produce a grain-oriented ceramic having the compound represented by formula (4) as a main phase, which does not substantially contain Bi as an a-site element.
Example 2 of a layered perovskite compound suitable as a material for the 2 nd anisotropically shaped powder is Sr 2 Nb 2 O 7 。Sr 2 Nb 2 O 7 The {010} plane of (2) has a smaller surface energy than other crystal planes, and has an excellent lattice matching with the pseudo-cubic {110} plane of the compound represented by formula (1). Thus, is composed of Sr 2 Nb 2 O 7 An anisotropically shaped powder having {010} plane as an orientation plane is suitable as a reactive template for producing a grain-oriented ceramic having {110} plane as an orientation plane.
The 3 rd embodiment of a layered perovskite compound suitable as the material of the 2 nd anisotropically shaped powder comprises Na 1.5 Bi 2.5 Nb 3 O 12 、Na 2.5 Bi 2.5 Nb 4 O 15 、Bi 3 TiNbO 9 、Bi 3 TiTaO 9 、 K 0.5 Bi 2.5 Nb 2 O 9 、CaBi 2 Nb 2 O 9 、SrBi 2 Nb 2 O 9 、BaBi 2 Nb 2 O 9 、BaBi 3 Ti 2 NbO 12 、 CaBi 2 Ta 2 O 9 、SrBi 2 Ta 2 O 9 、BaBi 2 Ta 2 O 9 、Na 0.5 Bi 2.5 Ta 2 O 9 、Bi 7 Ti 4 NbO 21 And Bi 5 Nb 3 O 15 And the like. Since the {001} plane of these compounds has a good lattice matching property with the pseudo-cubic {100} plane of the compound represented by the formula (1), the compound is composed of these compounds and has a {001} planeAnisotropically shaped powder as an orientation plane is suitable as a reactive template for producing grain-oriented ceramics having {100} plane as an orientation plane.
Example 4 of a layered perovskite-type compound suitable as the 2 nd anisotropically shaped powder includes Ca 2 Nb 2 O 7 And Sr 2 Ta 2 O 7 And the like. The {010} plane of these compounds has a good lattice matching with the pseudo-cubic {110} plane of the compound represented by formula (1). Therefore, anisotropically shaped powders comprising these compounds and having {010} plane as an orientation plane are suitable for the production of a powder having {110} plane as an orientation planeIs used as a reactive template for the grain-oriented ceramic of (1).
The method for producing the first anisotropically shaped powder is described below. The first anisotropically shaped powder, which contains a layered perovskite type compound having a predetermined composition, average particle diameter and/or aspect ratio (i.e., the 2 nd anisotropically shaped powder), can be easily produced by using a raw material containing component elements such as an oxide, carbonate, nitrate (hereinafter, referred to as "anisotropically shaped powder producing raw material"), and by heating together with a liquid or a substance which becomes a liquid by heating.
When the anisotropically shaped powder forming raw material is heated in a liquid phase in which atomic diffusion is easy, the 2 nd anisotropically shaped powder in which a plane having a small surface energy (for example, {1001} plane in the case of a substance represented by formula (4)) advances first can be easily synthesized. In this case, the average aspect ratio and the average particle diameter of the 2 nd anisotropically shaped powder can be controlled by appropriately selecting the synthesis conditions.
As the method for producing the anisotropically shaped powder of the 2 nd example, a suitable method comprises adding an appropriate flux such as NaCl, KCl, a mixture of NaCl and KCl, baCl to the anisotropically shaped powder-forming raw material 2 Or KF) and heating at a predetermined temperature (flux method), andthe process of producing the 2 nd anisotropically shaped powder which has an amorphous powder of the same composition and an aqueous alkali solution together in an autoclave (hydrothermal synthesis process).
On the other hand, since the anisotropy of the crystal lattice of the compound represented by formula (2) is extremely small, it is difficult to directly synthesize the first anisotropically molded powder (i.e., anisotropically molded powder a) which is composed of the compound represented by formula (2) and has a specific crystal plane as an orientation plane. However, the anisotropically shaped powder a may be produced by heating the 2 nd anisotropically shaped powder using it as a reactive template with a 2 nd reaction raw material satisfying predetermined conditions in a flux.
In the case of synthesizing the anisotropically shaped powder a using the 2 nd anisotropically shaped powder as a reactive template, when the reaction conditions were optimized, only the change in the crystal structure was caused, and the change in the shape of the powder hardly occurred. In addition, the average particle diameter and/or aspect ratio of the 2 nd anisotropically shaped powder is usually maintained constant before and after the reaction, but if the reaction conditions are optimized, the average particle diameter and/or aspect ratio of the anisotropically shaped powder a produced may be increased or decreased.
However, in order to easily synthesize the anisotropically shaped powder a which is easily oriented in one direction during molding, it is preferable that the 2 nd anisotropically shaped powder used for the synthesis also has a shape which is easily oriented in one direction during molding.
That is, when the anisotropically shaped powder a is synthesized using the 2 nd anisotropically shaped powder as a reactive template, the 2 nd anisotropically shaped powder also preferably has an average aspect ratio of at least 3 or more, more preferably 5 or more, and still more preferably 10 or more. On the other hand, in order to prevent pulverization in the subsequent step, the average aspect ratio is preferably 100 or less. Further, the average particle diameter of the 2 nd anisotropically shaped powder is preferably 0.05 μm to 20 μm, more preferably 0.1 μm to 10 μm.
The "2 nd reaction raw material" refers to a material which reacts with the 2 nd anisotropically shaped powder to produce an anisotropically shaped powder A comprising at least a compound represented by the formula (2). In this case, the 2 nd reaction raw material may be reacted with the 2 nd anisotropically shaped powder to produce only the compound represented by the formula (2), or may be reacted with the second anisotropically shaped powder to produce both the compound represented by the formula (2) and the remaining components. As used herein, "remaining components" refer to substances other than the compound represented by formula (2) to be targeted. When the 2 nd anisotropically shaped powder and the 2 nd reactive raw material form a residual component, the residual component is preferably made of a ceramic material which is easily removed by heat or chemical means.
As the form of the raw material for the 2 nd reaction, for example, oxide powder, composite oxide powder, salts such as carbonate, nitrate and oxalate, alkoxides and the like can be used. Further, the composition of the 2 nd reaction raw material is determined by the composition of the compound represented by the formula (2) to be produced and the composition of the 2 nd anisotropically shaped powder.
For example, 1 Bi of the bismuth layer-structured perovskite compound represented by the formula (4) is used 2.5 Na 0.5 Nb 2 O 9 (hereinafter, this is referred to as "BINN 2") and when the anisotropically shaped powder a of NN structure, which is one of the compounds represented by the formula (2), is synthesized, a compound containing Na (oxide, hydroxide, carbonate, nitrate) can be used as the 2 nd reaction raw material. In this case, a Na-containing compound corresponding to 1.5 moles of Na atoms may be added as the 2 nd reaction raw material with respect to 1 mole of BINN 2.
When an appropriate flux (for example, naCl, KCl, a mixture of NaCl and KCl, baCl) is added in an amount of 1 to 500 wt% based on the 2 nd anisotropically shaped powder and the 2 nd reaction raw material having such a composition 2 Or KF), heating to the eutectic point/melting point to form NN and Bi 2 O 3 Is the remaining component of the main component. Since Bi 2 O 3 Low melting point and acid resistance, and therefore, after removing the flux from the obtained reaction product by washing with water or the like,this was heated at a high temperature or acid-washed to obtain an anisotropically shaped powder A comprising NN having {100} planes as orientation planes.
Further, for example, K, which is one of the compounds represented by formula (2), is synthesized using 2 nd anisotropically shaped powder composed of BINN2 0.5 Na 0.5 NbO 3 (hereinafter, this is referred to as "KNN") can be used as the 2 nd reaction raw material in the case of the anisotropically shaped powder A comprising Na-containing compounds (e.g., oxides, hydroxides, carbonates, nitrates) and K-containing compounds (e.g., oxides, hydroxides, nitrates)Compound, carbonate, nitrate), or a compound containing both Na and K. In this case, a Na-containing compound corresponding to 0.5 mol of Na atoms and a K-containing compound corresponding to 1 mol of K atoms may be added as the 2 nd reaction raw materials with respect to 1 mol of BINN 2.
When an appropriate flux is added in an amount of 1 to 500 wt% to the 2 nd anisotropically shaped powder and the 2 nd reaction raw material having such a composition, KNN and Bi are generated by heating to a eutectic point-melting point 2 O 3 The remaining component of the main component, thus removing the flux and Bi from the resultant reaction mixture 2 O 3 This gives an anisotropically shaped powder A comprising KNN with the {100} plane as the orientation plane.
As in the case where only the compound represented by formula (2) is produced by reacting the 2 nd anisotropically shaped powder with the 2 nd reactive raw material, the 2 nd anisotropically shaped powder having a predetermined composition and the 2 nd reactive raw material having a predetermined composition may be heated in an appropriate co-solvent. In this way, the compound represented by the formula (2) having the desired composition is produced in the flux. Further, when the flux is removed from the obtained reaction product, an anisotropically shaped powder A composed of the compound represented by the formula (2) and having a specific crystal plane as an orientation plane is obtained.
Since the anisotropy of the crystal lattice of the compound represented by formula (2) is small, it is difficult to directly synthesize anisotropically shaped powder a, and it is also difficult to directly synthesize anisotropically shaped powder a having an arbitrary crystal plane as an orientation plane.
On the other hand, since the crystal lattice of the layered perovskite compound has large anisotropy, it is possible to easily synthesize an anisotropically shaped powder directly. Similarly, in many cases, the orientation plane of the anisotropically shaped powder composed of a layered perovskite compound often has lattice matching with the specific crystal plane of the compound represented by formula (2). Further, the compound represented by formula (2) is thermodynamically more stable than the layered perovskite compound.
Therefore, when the 2 nd anisotropically shaped powder composed of a layered perovskite type compound and having an orientation plane lattice-matched to the specific crystal plane of the compound represented by formula (2) and the 2 nd reaction raw material are reacted in an appropriate flux, the 2 nd anisotropically shaped powder can be easily synthesized to function as a reactive template, and anisotropically shaped powder a composed of the compound represented by formula (2) which inherits the orientation direction of the 2 nd anisotropically shaped powder can be synthesized.
Further, if the compositions of the 2 nd anisotropically shaped powder and the 2 nd reaction raw material are optimized, the a-site elements contained in the 2 nd anisotropically shaped powder (hereinafter, referred to as "remaining a-site elements") are discharged simultaneously as remaining components, and anisotropically shaped powder a composed of a compound represented by formula (2) containing no remaining a-site elements is produced.
Particularly when the 2 nd anisotropically shaped powder is composed of a bismuth layer-structured perovskite compound represented by the formula (4), bi is discharged as the remaining A site element to produce Bi 2 O 3 Is the main component and the rest component. Therefore, when the remaining components are removed by a thermal or chemical method, an anisotropically shaped powder a substantially free of Bi, composed of the compound represented by formula (2), and having a specific crystal plane as an orientation plane is obtained.
The method of making the grain-oriented ceramic is described below.
In the method for producing a grain-oriented ceramic, the grain-oriented ceramic is produced by the mixing step, the molding step, and the heat treatment step described above.
A mixing step of mixing (i) a first anisotropically shaped powder containing oriented fine particles having orientation planes on specific crystal planes and (ii) producing { Li by reaction with the first anisotropically shaped powder x (K 1-y Na y ) 1-x }(Nb 1-z-w Ta z Sb w )O 3 (wherein 0. Ltoreq. X. Ltoreq.0.2, 0. Ltoreq. Y. Ltoreq.1, 0. Ltoreq. Z. Ltoreq.0.4, 0. Ltoreq. W. Ltoreq.0.2, and x + z + w > 0) and (iii) any one or more additional elements selected from the group consisting of metal elements belonging to groups 2 to 15 of the periodic Table of elements, semimetal elements, transition metal elements, noble metal elements, and alkaline earth metal elements, thereby producing a raw material mixture,
in the first anisotropically shaped powder, the oriented planes of the oriented fine particles have lattice matching with the specific crystal planes of the compound represented by formula (1). As the first anisotropically shaped powder, the anisotropically shaped powder a described above, the anisotropically shaped powder 2, and the like can be used.
The first reaction material is reacted with the first anisotropically shaped powder to produce at least a compound of the compound represented by formula (1). In this case, the first reaction raw material may produce the compound represented by formula (1) alone or produce the compound represented by formula (1) and the remaining components simultaneously due to the reaction with the first anisotropically shaped powder. In the case where the surplus component is generated from the first anisotropically shaped powder and the first reactive material, it is preferable that the surplus component be a substance that is easily removed by heating or a chemical method.
The composition of the first reaction raw material is determined by the composition of the first anisotropically shaped powder and the composition of the compound represented by formula (1) to be produced. Further, as the first reaction raw material, for example, oxide powder, composite oxide powder, hydroxide powder, salts such as carbonate, nitrate, and oxalate or alkoxide can be used.
More specifically, for example, when an anisotropically shaped powder a having a KNN composition or an NN composition is used as the first anisotropically shaped powder to produce a grain-oriented ceramic composed of a compound represented by formula (1), a mixture of compounds containing at least one element of Li, K, na, nb, ta, and Sb is used as the first reaction raw material, and the anisotropically shaped powder a and the first reaction raw material produce a compound of formula I having a target composition.
Further, for example, when a 2 nd anisotropically shaped powder having a composition represented by formula (4) is used as the first anisotropically shaped powder to produce a grain-oriented ceramic composed of a compound represented by formula (1), a mixture of compounds containing at least one element of Li, K, na, nb, ta, and Sb is used as the first reaction raw material, and these are mixed in a stoichiometric composition to produce the compound represented by formula (1) having a desired composition from the 2 nd anisotropically shaped powder and the first reaction raw material. But also can be applied to the production of grain-oriented ceramics with other compositions.
The oriented fine particles preferably have a tabular morphology (claim 17).
In this case, a molded body can be easily produced in a molding step described later, so that the orientation planes of the first anisotropic-morphology powder are oriented in almost the same direction in the molded body.
The oriented particles preferably comprise formula (2): { Li x (K 1-y Na y ) 1-x }(Nb 1-z-w Ta z Sb w )O 3 (wherein 0. Ltoreq. X.ltoreq.1, 0. Ltoreq. Y.ltoreq.1, 0. Ltoreq. Z.ltoreq.1, and 0. Ltoreq. W.ltoreq.1) (claim 18).
In this case, a grain-oriented ceramic having a high degree of orientation can be produced.
That is, as described above, the compound represented by formula (2) has good lattice matching with the compound represented by formula (1), and therefore, the anisotropic form powder containing the oriented fine particles represented by formula (2) having a specific plane can be used as a good reaction template for a ceramic reaction to produce a ceramic having excellent crystal grain orientation.
The orientation plane of the oriented particles is preferably a pseudo-cubic {100} plane (claim 19).
In this case, in the tetragonal crystal region, the orientation axis and the polarization axis are coincident, so that the temperature dependence of the displacement generated under a large electric field can be improved.
In the mixing step, any one or more elements selected from the group consisting of metal elements belonging to groups 2 to 15 of the periodic table, semimetal elements, transition metal elements, noble metal elements, and alkaline earth metal elements are added to the mixed first anisotropically shaped powder and first reaction raw materials at a predetermined ratio.
The additional element may be added in an amount of 0.0001 to 0.15 mole per mole of the compound represented by formula (1) to be produced.
If the additional element is added in an amount of less than 0.0001 mol or more than 0.15 mol, the piezoelectric characteristics or dielectric characteristics of the grain-oriented ceramics may be degraded.
The additional element may be added as an additional element, but may also be added in the form of a compound containing the additional element.
Further, an additional element may be added so as to adjust the additional element by replacing a part of Li, K, na, nb, ta and Sb in the compound represented by formula (1). In order to adjust the additional elements by substitution, for example, the raw materials may be mixed in a stoichiometric ratio to replace the added elements.
More specifically, for example, when Li of the compound represented by formula (1) is substituted with an additional element, the amount of the Li-containing compound in the first anisotropic morphology powder or the first reaction raw material is reduced, and an amount of the additional element or the compound containing the additional element for compensating for the reduction is added and mixed while obtaining the stoichiometric ratio for producing the whole of the compound represented by formula (1), whereby substitution can be achieved. Also in the case of replacing other atoms such as K, na, nb, ta and Sb in the compound represented by the formula (1), the amount of the compound containing these atoms is reduced in the first anisotropic morphology powder or the first reaction raw material, and an additional element for replacing the atoms or the compound containing the additional element is added to compensate for the reduced portion, whereby the replacement can be carried out.
Additional elements may also be added from the surface. The additional element is added from the surface to the crystal grains containing the compound represented by formula (1) or to the crystal grain boundary in the form of another single element or a compound containing the additional element.
The additional element is preferably any one or more elements selected from the group consisting of Mg, ca, sr, ba, sc, ti, V, cr, mn, fe, co, ni, cu, zn, Y, zr, mo, ru, rh, pd, ag, hf, W, re, pt, au, ir, os, B, al, ga, in, si, ge, sn and Bi.
In this case, the piezoelectric characteristics or dielectric characteristics of the obtained grain-oriented ceramic can be improved.
In the mixing step, in addition to the first anisotropically shaped powder, the first reaction raw material, and the additional element mixed at a predetermined ratio, an amorphous fine powder (hereinafter, referred to as "compound powder") having a compound constitution identical to the compound represented by formula (1) obtained by the reaction thereof and/or a sintering aid such as CuO may be added simultaneously. The addition of fine compound powder or sintering aid is advantageous because the density of the sintered body can be increased more easily.
In the case of mixing the fine compound powder, if the mixing ratio of the fine compound powder is too large, the mixing ratio of the first anisotropically shaped powder to the whole raw material is inevitably reduced, and the degree of orientation of the specific crystal plane may be lowered. Therefore, the mixing ratio of the fine compound powder is preferably selected to be optimum in accordance with the required density and orientation degree of the sintered body.
The mixing ratio of the first anisotropically shaped powder is composed of one to more component elements in the first anisotropically shaped powder, preferably ABO 3 The A site of the compound represented by the formula (1) is contained in a ratio of 0.01 to 70 at%, more preferably 0.1 to 50 at%. Further, 1 to 10 atoms are more preferableAnd (5) percent of children.
The mixing of the first anisotropically shaped powder and the first reactive material, and if necessary, the compound fine powder and the sintering aid may be dry mixing or wet mixing by adding an appropriate dispersion medium such as water or alcohol. At this time, a binder and/or a plasticizer may be added if necessary.
The molding step will be described below.
A molding step of molding the raw material mixture so that the orientation planes of the first anisotropically shaped powder are oriented in almost the same direction in a molded body.
At this time, the molding may be performed so that the first anisotropically shaped powder is oriented in plane, or the molding may be performed so that the first anisotropically shaped powder is oriented in axis.
It suffices if the shaping method is a method that is capable of orienting the first anisotropically shaped powder. Specific examples of preferable molding methods for orienting the powder surface of the first anisotropic molding include a doctor blade method, a press molding method, a rolling method, and the like. Further, as a preferable molding method for orienting the powder axis of the first anisotropic molding, specific examples include an extrusion molding method, a centrifugal molding method, and the like.
In order to increase the thickness of the powder surface-oriented molded body of the first anisotropic molding (hereinafter, referred to as "surface-oriented molded body"), for example, or to improve the degree of orientation, the surface-oriented molded body may be subjected to a treatment such as lamination, pressing, or rolling (hereinafter, referred to as "surface-oriented treatment") in one step.
In this case, any one kind of surface orientation treatment may be performed on the surface-oriented molded article, but 2 or more kinds of surface orientation treatment may be performed. Further, the surface-oriented molded article may be subjected to 1 kind of surface orientation treatment repeatedly, or may be subjected to 2 or more kinds of surface orientation treatments repeatedly.
The heat treatment step is explained below.
A heat treatment step of heating the molded body to react the first anisotropically shaped powder with the first reaction raw material, thereby producing a polycrystalline body which contains an isotropic perovskite compound represented by formula (1) and whose crystal grains are oriented and exhibit a texture structure.
In the heat treatment step, the molded body is heated to produce an isotropic perovskite-type compound represented by formula (1), and at the same time, the isotropic perovskite-type compound is sintered. At this time, an additional element may be added so as to displace a part of Li, K, na, nb, ta and Sb in the compound represented by formula (1) or to distribute them on crystal grains and/or crystal grain boundaries containing a polycrystal of the compound represented by formula (1).
In the heat treatment step, the remaining components are also simultaneously produced depending on the composition of the first anisotropically shaped powder and/or the first reaction material.
As for the heat treatment step, in order to allow the reaction and/or sintering to proceed efficiently and to produce a reactant having a desired composition, the heating temperature may be selected to be optimized, for example, according to the first anisotropically shaped powder or first reaction raw material used, the composition of the grain-oriented ceramic to be produced, and the like.
For example, in the case of producing a grain-oriented ceramic composed of the compound represented by formula (1) using anisotropically shaped powder A having a KNN composition, heating may be performed at 900 to 1300 ℃. In this temperature range, the optimum heating temperature differs depending on the composition of the compound represented by formula (1). The heating time may be selected to be optimum depending on the heating temperature in order to obtain a predetermined density of the sintered body.
Further, in the case where a surplus component is generated as a result of the reaction of the first anisotropically shaped powder and the first reaction raw material, the surplus component may be left as a secondary phase in the sintered body, or may be removed from the sintered body, and therefore examples of the method include a method of heat removal and a method of chemical removal.
The method of heat removal includes, for example, a method of heating a sintered body formed of the compound represented by formula (1) and the remaining components (hereinafter, referred to as "intermediate sintered body") to a predetermined temperature to thereby volatilize the remaining components. More specifically, a method of heating the intermediate sintered body for a long time at a temperature at which the remaining components are volatilized under reduced pressure or in oxygen is preferable.
The heating temperature at which the remaining components are removed with heat may be selected to an optimum temperature depending on the composition of the compound represented by formula (1) and/or the remaining components, so that the remaining components can be efficiently volatilized and the production of by-products can be suppressed. For example, when the remaining component is a bismuth oxide single phase, the heating temperature is preferably 800 to 1300 ℃, more preferably 1000 to 1200 ℃.
On the other hand, examples of the method of chemically removing the residual component include a method of immersing the intermediate sintered body in a treatment liquid having a property of etching only the residual component and filtering out the residual component. As for the treatment liquid used herein, an optimum treatment liquid may be selected in accordance with the composition of the compound represented by formula (1) and/or the remaining components. For example, in the case where the remaining component is a bismuth oxide single phase, an acid such as nitric acid or hydrochloric acid is preferably used as the treatment liquid. Nitric acid is particularly suitable as a treatment liquid for chemical extraction of the remaining components, which are based on bismuth oxide.
The reaction of the first anisotropically shaped powder with the first reactive material and the removal of the remaining components may be carried out in any time manner, i.e. simultaneously, successively or individually. For example, the molded body may be directly heated under reduced pressure or vacuum to a temperature at which both the reaction of the first anisotropically shaped powder with the first reaction raw material and the volatilization of the remaining components effectively proceed, and the removal of the remaining components may be carried out simultaneously with the reaction. In some cases, the compound represented by formula (1) in which the additional element is used to replace the objective composition may be positioned on the crystal grains and/or the grain boundaries at the time of the reaction of the first anisotropically shaped powder and the first reaction raw material.
For example, the remaining components may be removed by heating the molded body in the atmosphere or in oxygen at a temperature at which the reaction of the first anisotropically shaped powder and the first reaction raw material effectively proceeds to produce an intermediate sintered body, and then heating the intermediate sintered body under reduced pressure or in vacuum at a temperature at which volatilization of the remaining components effectively proceeds. Alternatively, the intermediate sintered body may be heated for a long time in the atmosphere or in oxygen immediately after the intermediate sintered body is produced at a temperature at which volatilization of the remaining components effectively proceeds, thereby removing the remaining components.
Further, for example, after the intermediate sintered body is formed and cooled to room temperature, the intermediate sintered body may be immersed in a treatment liquid to chemically remove the remaining components, or after the intermediate sintered body is formed and cooled to room temperature, the intermediate sintered body may be heated again to a predetermined temperature in a predetermined atmosphere to remove the remaining components by heat.
In the case of a molded body containing a binder, heat treatment for the main purpose of degreasing may be performed before the heat treatment step, and in this case, the temperature of degreasing may be a temperature sufficient to thermally decompose at least the binder. However, when the raw material contains a volatile substance (for example, a Na compound), the degreasing is preferably performed at 500 ℃ or less.
Further, if degreasing of the oriented molded body is performed, the degree of orientation of the first anisotropically molded powder in the oriented molded body is lowered, or volume expansion may occur in the oriented molded body. In this case, it is preferable to perform hydrostatic pressure (CIP) treatment on the oriented molded article after degreasing and before heat treatment. This treatment can prevent the decrease in the density of the sintered body due to the decrease in the degree of orientation caused by degreasing or the volume expansion of the oriented molded body.
Further, in the case where the first anisotropically shaped powder is reacted with the first reaction raw material to produce a surplus component and the surplus component is removed, the intermediate sintered body from which the surplus component is removed may be further subjected to hydrostatic pressure treatment and re-sintered. Meanwhile, in order to further increase the density and orientation degree of the sintered body, it is effective to further hot press the sintered body after the heat treatment. Further, methods such as addition of compound fine powder, CIP treatment, hot pressing, and the like may be used in combination.
In the production method of the sixth invention, it is also possible to easily synthesize 2 nd anisotropic form powder containing a layered perovskite compound by using anisotropic form powder a containing a compound represented by formula (2) as a reaction template, and then produce a crystal grain oriented ceramic by using anisotropic form powder a as a reaction template. According to this method, even in the case of having a compound represented by formula (1) having small lattice anisotropy, a grain-oriented ceramic in which an arbitrary crystal plane is oriented can be easily produced at low cost.
Further, when the 2 nd anisotropic form powder and the 2 nd reaction raw material are optimized in composition, even the anisotropic form powder a containing no remaining a-site element can be produced. Therefore, the composition control of the element at the A site is easier, and even grain-oriented ceramics having a compound represented by formula (1) having a composition that could not be obtained by the conventional method as the main phase can be produced.
Similarly, the perovskite compound including the layered 2 nd anisotropic morphology powder can be used as the first anisotropic morphology powder. In this case, the compound represented by formula (1) can be synthesized by simultaneous sintering in the heat treatment step. Further, when the first anisotropic morphology powder oriented in the molded body and the components of the first reaction raw material to be reacted therewith are optimized, not only the compound represented by formula (1) is synthesized, but also the remaining a-site elements can be discharged as a remaining component from the 2 nd anisotropic molded powder.
Further, when the 2 nd anisotropically shaped powder which produces residual components which are easily removed by heating or chemical treatment is used as the first anisotropically shaped powder, a grain-oriented ceramic which contains substantially no residual a-site element, is composed of the compound represented by formula (1), and has a particular crystal plane orientation is produced.
[ examples ]
[ example 1]
Examples of grain-oriented ceramics according to the invention are described below.
The grain-oriented ceramic of the present embodiment comprises a main phase including a polycrystal for each mole of { Li 0.03 (K 0.5 Na 0.5 ) 0.97 }(Nb 0.80 Ta 0.20 )O 3 The anisotropic perovskite-type compound represented contained 0.01 mol of Pd as an additional element. In the grain-oriented ceramic of the present invention, the specific crystal planes of the respective crystal grains constituting the polycrystalline body are oriented.
In the ceramic manufacturing method of this embodiment, the mixing step, the molding step, and the heat treatment step are performed.
In the mixing step, the first anisotropically shaped powder contains oriented fine particles having oriented planes on specific crystal planes, and the first reaction raw material reacts with the first anisotropically shaped powder to produce { Li { 0.03 (K 0.5 Na 0.5 ) 0.97 }(Nb 0.80 Ta 0.20 )O 3 And mixing a compound containing Pd as an additional element to produce a raw material mixture.
In the molding step, the raw material mixture is molded so that the oriented planes of the first anisotropic morphology powder are oriented in almost the same direction in the molded body.
In the heat treatment step, the molded body is heated to react the first anisotropic morphology powder with the first reaction raw material to produce a catalyst containing { Li [ ] 0.03 (K 0.5 Na 0.5 ) 0.97 }(Nb 0.80 Ta 0.20 )O 3 The polycrystalline sintered body of (2), wherein the crystal grain planes are oriented.
Further, in the mixing step, each mole of { Li } 0.03 (K 0.5 Na 0.5 ) 0.97 }(Nb 0.80 Ta 0.20 )O 3 0.01 mole of additional elements were added.
In the oriented fine particles, the orientation plane is an orientation plane occupying the largest area in the oriented fine particles. The oriented fine particle oriented surface has lattice matching with a certain oriented surface among crystal grains constituting the polycrystalline sintered body obtained after the heat treatment step.
The method for producing the grain-oriented ceramic of this embodiment is specifically described below.
(1) Synthesis of NN plate-like powder
In stoichiometric ratio of Bi 2.5 Na 3.5 Nb 5 O 18 (hereinafter, this is referred to as "BINN 5") and Bi each having a purity of 99.99% or more was weighed 2 O 3 Powder, na 2 CO 3 Powder and Nb 2 O 5 The powders were wet-mixed, 50 wt% NaCl as a flux (flux) was added to the raw materials, and dry-mixed for 1 hour.
The obtained mixture was put into a platinum crucible, heated at 850 ℃ for 1 hour, and after the flux was completely melted, further heated at 1100 ℃ for 2 hours to synthesize BINN5. Here, both the temperature-raising rate and the cooling rate were 200 ℃ per hour. After cooling, the fluxing agent was removed from the reaction by hot water washing to give a BINN5 powder. The BINN5 powder thus obtained was a plate-like powder having a {001} plane as an orientation plane.
Subsequently, synthetic NN (NaNbO) was added to the BINN5 plate-like powder 3 ) Required amount of Na 2 CO 3 The powders were mixed and heat-treated in a platinum crucible at 950 ℃ for 8 hours with NaCl as a flux.
In the obtained reaction product, bi is contained in addition to the NN powder 2 O 3 . Therefore, after removing the flux from the reaction mass, it was put into HNO 3 In (1N), bi produced as a residual component 2 O 3 The solution was filtered, and the NN powder was separated and washed with ion-exchanged water at 80 ℃. Obtained NN powderAnd a plate-like powder (flat NN powder) having a pseudo-cubic {100} plane as an orientation plane, a particle diameter of 10 to 20 μm, and an aspect ratio of 10 to 20 or so. Hereinafter, the flat NN powder is used as the first anisotropic morphology powder (template).
(2) Having { Li 0.03 (K 0.5 Na 0.5 ) 0.97 }(Nb 0.80 Ta 0.20 )O 3 Synthesis of compositionally grain-oriented ceramics
The flat NN powder, non-flat NN powder, KN powder, KT (KTaO) produced above were mixed 3 ) Powder and LT (LiTaO) 3 ) Powders, as first reaction powders, mixed in stoichiometric ratios to give the desired component, i.e., { Li 0.03 (K 0.5 Na 0.5 ) 0.97 }(Nb 0.80 Ta 0.20 )O 3 Then further synthesizing { Li 0.03 (K 0.5 Na 0.5 ) 0.97 }(Nb 0.80 Ta 0.20 )O 3 And Pd-containing PdO powder having a purity of 99.99% or more as a component of an additional element at a ratio of 0.01 mol per mol ratio, the powder was subjected to wet mixing for 20 hours.
To the resulting slurry and 1 mol of { Li synthesized from the starting materials 0.03 (K 0.5 Na 0.5 ) 0.97 }(Nb 0.80 Ta 0.20 )O 3 10.35g of binder (Sekisui chemical Limited)Manufactured, esec (registered trademark) BH-3), and 10.35g of a plasticizer (butyl phthalate), followed by mixing for an additional 2 hours.
Here, the NN plate-like powder (template) was mixed in such an amount that: synthesis of { Li from starting Material 0.03 (K 0.5 Na 0.5 ) 0.97 }(Nb 0.80 Ta 0.20 )O 3 5 atomic% of the a-site element of (a) is the amount of sodium supplied from the NN plate-like powder.
Further, the NN powder, KN powder, KT powder and LT powder in a non-plate form are obtained by mixing a predetermined amount of K having a purity of 99.99% or more 2 CO 3 Powder, na 2 CO 3 Powder, nb 2 O 5 Powder, ta 2 O 5 Powder and Li 2 CO 3 A mixture of powders is heated at 750 ℃ for 5 hours, and the reaction product is pulverized by a ball mill.
The slurry thus mixed was molded into a tape (tape) having a thickness of 100 μm using a blade device (tape casting method), and the tape was laminated, pressed and rolled to obtain a sheet-like molded article having a thickness of 1.5 mm. Then, the obtained plate-like molded body was heated in the air to degrease. The obtained plate-like molded body was degreased in the atmosphere under the conditions of temperature rise of 600 ℃ and heating rate of 50 ℃/hr, heating time of 2 hours at 600 ℃ and cooling rate of furnace cooling.
Further, the degreased plate-like molded body was subjected to CIP treatment under a pressure of 300MPa, and then was subjected to atmospheric pressure sintering by heating in oxygen. Raising the temperature to 1,000-1,200 deg.C under a temperature raising speed of 200 deg.C/hr, heating (baking) the formed body for 1-5 hr, and sintering under normal pressure or hot pressing at a cooling speed of 200 deg.C/hr (under an applied pressure of 35 kg/cm) 2 ). At this time, as for the burning temperature and the firing time, the density of the sintered body can be maximized by selecting the sintering conditions under which firing is performed at 1,000 to 1,200 ℃ for 1 to 5 hours, and the relative density of the sintered body produced is 95% or more.
Thus, grain-oriented ceramics are produced. The grain-oriented ceramic is referred to as sample E1.
In sample E1, the additional element Pd was added from the surface in the form of a Pd-containing compound PdO. Therefore, the additional element Pd in sample E1 exists in the presence of { Li } 0.03 (K 0.5 Na 0.5 ) 0.97 }(Nb 0.80 Ta 0.20 )O 3 On the crystal grains or the crystal grain boundaries of the polycrystalline sintered body.
(example 2)
This example was to produce a crystalline ceramic containing Ni as an additional element.
In this example, similarly to example 1, tabular NN powder, non-tabular NN powder, KN powder, KT powder and LT powder were mixed in a stoichiometric ratio to obtain the objective component, i.e., { Li } 0.03 (K 0.5 Na 0.5 ) 0.97 }(Nb 0.80 Ta 0.20 )O 3 A NiO powder having a purity of 99.99% or more, which has a Ni-containing compound as an additional element, and then further comprises { Li 0.03 (K 0.5 Na 0.5 ) 0.97 }(Nb 0.80 Ta 0.20 )O 3 And NiOThe powders were mixed at a ratio of 0.01 mol per mol, and wet-mixed for 20 hours.
Similarly to example 1, a dense grain-oriented ceramic having a relative density of 95% or more was produced by adding a binder and a plasticizer, mixing the resultant slurry, molding, degreasing, and heating (firing). This is referred to as sample E2.
That is, sample E2 was prepared in the same manner as sample E1 of example 1, except that Ni was mixed as an additional element.
In sample E2, the additional element Ni was added from the surface in the form of a Ni-containing compound NiO. Therefore, the additional element Ni in sample E2 exists in the presence of { Li [ ] 0.03 (K 0.5 Na 0.5 ) 0.97 }(Nb 0.80 Ta 0.20 )O 3 Crystal grains or grain boundaries of the polycrystalline sintered body.
(example 3)
This example was made such that the major phase was comprised of { Li 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 And a polycrystalline sintered body containing In.
In this example, similarly to example 1, a tabular NN powder, a non-tabular NN powder, a KN powder, and a KT powder were prepared. And LS (LiSbO) is to be prepared 3 ) And (3) powder. LS powder was produced similarly to NN powder, KN powder and KT powder by adding Li in a predetermined amount 2 CO 3 Powder and Sb 2 CO 5 The mixture of powders was heated at 750 ℃ for 5 hours and the reaction product was obtained by a solid phase method in which the reaction product was pulverized by a ball mill.
These tabular NN powder, non-tabular NN powder, KN powder, KT powder, LS powder and NS powder were mixed in a stoichiometric ratio to obtain a target composition, that is, { Li 0.04 (K 0.5 Na 0.5 ) 0.96 } (Nb 0.86 Ta 0.10 Sb 0.04 )O 3 In having a purity of 99.99% or more 2 O 3 The powder is used as an In-containing compound, is used as an additional element, and then further In 2 O 3 Powder with { Li 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 The powders were mixed at a ratio of 0.005 mol per mol, and wet-mixed for 20 hours. Sometimes, by this method, at every mole of { Li } 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 0.005 mol of In was mixed therein 2 O 3 And 0.01 mol of In was mixed.
Similarly to example 1, dense grain-oriented ceramics having a relative density of 95% or more were produced by adding a binder and a plasticizer, mixing the resultant slurry, molding, degreasing and heating (firing). This is referred to as sample E3.
In sample E3, the additional element In is In the form of an In-containing compound 2 O 3 Is added from the surface. Therefore, the additional element In sample E3 exists In the region containing { Li 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 Crystal grains or grain boundaries of the polycrystalline sintered body.
(example 4)
This example is an example of producing a grain-oriented ceramic whose main phase is Li including Ca added thereto to replace part of K and Na 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 The polycrystalline sintered body of (4).
Similarly to example 3, in this example, tabular NN powder, non-tabular NN powder, KN powder, KT powder, and LS powder were prepared. CaCO prepared in the same manner 3 The powder has a purity of 99.99% or more, which is a Ca-containing compound as an additional element.
Mixing the raw materials in stoichiometric ratio to obtain { Li 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 Ca was added to obtain a complex of K and Na substituted by a portion { Li 0.04 (K 0.5 Na 0.5 ) 0.94 Ca 0.01 } (Nb 0.86 Ta 0.10 Sb 0.04 )O 3 Then, wet mixing was performed for 20 hours.
Similarly to example 1, dense grain-oriented ceramics having a relative density of 95% or more were produced by adding a binder and a plasticizer, mixing the resultant slurry, molding, degreasing and heating (firing). This is referred to as sample E4.
In sample E4, an additional element Ca was added thereto so that { Li is substituted 0.04 (K 0.5 Na 0.5 ) 0.96 } (Nb 0.86 Ta 0.10 Sb 0.04 )O 3 The moiety K and Na at position A. The added additional element Ca accounts for the whole { Li 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 1 atomic% of the number of A positions.
(example 5)
This example is an example of producing a grain-oriented ceramic whose main phase is comprised of { Li 0.04 (K 0.5 Na 0.5 ) 0.96 } (Nb 0.86 Ta 0.10 Sb 0.04 )O 3 And a polycrystalline sintered body containing Si.
In this example, similarly to example 3, flat plate-like NN powder, non-flat plate-like NN powder, KN powder, KT powder, and LS powder were prepared.
Mixing the raw materials in stoichiometric proportions to obtain the target composition, i.e., { Li 0.04 (K 0.5 Na 0.5 ) 0.96 } (Nb 0.86 Ta 0.10 Sb 0.04 )O 3 SiO having a purity of 99.99% or more 2 The powder is a Si-containing compound, is used as an additional element, and then 0.01 mol SiO is further added 2 Powder and per mole { Li 0.04 (K 0.5 Na 0.5 ) 0.96 } (Nb 0.86 Ta 0.10 Sb 0.04 )O 3 The powders were mixed and wet-mixed for 20 hours.
Similarly to example 1, a dense grain-oriented ceramic having a relative density of 95% or more was produced by adding a binder and a plasticizer, mixing the resultant slurry, molding, degreasing, and heating (firing). This is referred to as sample E5.
In sample E5, the additional element Si is a Si-containing compound SiO 2 Is added from the surface. Therefore, the additional element Si in sample E5 exists in the presence of { Li [ ] 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 On the crystal grains or the crystal grain boundaries of the polycrystalline sintered body.
(example 6)
This example is an example of producing a grain-oriented ceramic whose main phase is comprised of { Li 0.04 (K 0.5 Na 0.5 ) 0.96 } (Nb 0.86 Ta 0.10 Sb 0.04 )O 3 And a polycrystalline sintered body containing Ag.
In this example, similarly to example 3, a flat plate-like NN powder, a tri-flat plate-like NN powder, a KN powder, a KT powder, and a LS powder were prepared.
Mixing the raw materials in stoichiometric proportions to obtain the target composition, i.e., { Li 0.04 (K 0.5 Na 0.5 ) 0.96 } (Nb 0.86 Ta 0.10 Sb 0.04 )O 3 Then Ag thereafter 2 O powder having a purity of 99.99% or more, used as an additional element as an Ag-containing compound, and then further processed at each mole of { Li } 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 The powder was wet-mixed for 20 hours while mixing 0.005 mol. Sometimes, by this method, at every mole of { Li } 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 Mixing 0.005 mol Ag 2 O and 0.01 mol Ag.
Similarly to example 1, a dense grain-oriented ceramic having a relative density of 95% or more was produced by adding a binder and a plasticizer, mixing the resultant slurry, molding, degreasing, and heating (firing). This is referred to as sample E6.
In sample E6, the additional element Ag is a compound Ag containing Ag 2 The form of O is added from the surface. Therefore, the additional element Ag in sample E6 exists in the sample containing { Li 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 On the crystal grains or the crystal grain boundaries of the polycrystalline sintered body.
(example 7)
This example is an example of producing a grain-oriented ceramic, the main phase comprising a polycrystalline sintered body having the same composition as in example 6, being a tabular powder and (Li) 0.0421 K 0.5053 Na 0.4526 )(Nb 0.8526 Ta 0.1053 Sb 0.421 )O 3 Obtained by reaction.
In the same manner as in example 1, a flat NN powder was prepared.
Subsequently, (Li) 0.0421 K 0.5053 Na 0.4526 )(Nb 0.8526 Ta 0.1053 Sb 0.421 )O 3 The powder is based on a mixture containing a predetermined amount of K and each having a purity of 99.99% or more 2 CO 3 Powder, na 2 CO 3 Powder, nb 2 O 5 Powder, ta 2 O 5 Powder, li 2 CO 3 Powder and Sb 2 O 5 A solid phase method in which a mixture of the powders is heated at 750 ℃ for 5 hours and the reaction product is pulverized by a ball mill.
Thereafter, the flat NN powders and (Li) 0.0421 K 0.5053 Na 0.4526 )(Nb 0.8526 Ta 0.1053 Sb 0.421 )O 3 The powders were mixed with the starting materials in stoichiometric proportions to give the target composition, i.e., { Li 0.04 (K 0.5 Na 0.5 ) 0.96 } (Nb 0.86 Ta 0.10 Sb 0.04 )O 3 Thereafter by preparing Ag-containing compounds Ag 2 O is used as an additional element, and then further per mol of { Li 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 With 0.005 mol Ag 2 O mixing and pulverizingWet mixing was not carried out for 20 hours.
Here, similarly to example 1, the flat plate-like NN powder (template) was mixed, and thus the amount of the additional element Na added accounted for the synthesis of { Li } NN powder provided from the starting material in a flat plate-like NN powder 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 The number of A positions in (C) is 5 atom%.
Similarly to example 1, grain-oriented ceramics having a relative density of 95% or more were produced by adding a binder and a plasticizer, mixing the resultant slurry, molding, degreasing, and heating (firing). This is sample E7.
In sample E7, the additional element Ag was 99.99% by weight of Ag 2 O powder (which is an Ag-containing compound) was added from the surface, and thus the additional element Ag in sample E7 existed to contain { Li [ ] 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 Crystal grains or grain boundaries of the polycrystalline sintered body.
(example 8)
This example is an example of producing a grain-oriented ceramic whose main phase is Li including Sr added to replace part of K and Na 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 The polycrystalline sintered body of (4).
In this example, similarly to example 3, flat plate-like NN powder, non-flat plate-like NN powder, KN powder, KT powder, and LS powder were prepared. SrCO prepared in the same way 3 The powder has a purity of 99.99% or more, which is an Sr-containing compound as an additional element.
Mixing the raw materials in stoichiometric ratio to obtain { Li 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 Sr is added to replace part of K and Na to obtain a complex { Li 0.04 (K 0.5 Na 0.5 ) 0.94 Sr 0.01 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 Then, wet mixing was performed for 20 hours.
Similarly to example 1, grain-oriented ceramics having a relative density of 95% or more were produced by adding a binder and a plasticizer, mixing the resultant slurry, molding, degreasing, and heating (firing). This refers to sample E8.
In sample E8, additional element Sr was added to replace { Li 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 The moiety K and Na at position A. The added additional element Sr accounts for the whole of the { Li 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 1 atom% of the total of the A sites.
(example 9)
This example is an example of producing a grain-oriented ceramic whose main phase is comprised of { Li 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 And a Pd-containing polycrystalline sintered body.
In this example, similarly to example 3, flat plate-like NN powder, non-flat plate-like NN powder, KN powder, KT powder, and LS powder were prepared.
Mixing the raw materials in stoichiometric proportions to obtain the target composition, i.e., { Li 0.04 (K 0.5 Na 0.5 ) 0.96 } (Nb 0.86 Ta 0.10 Sb 0.04 )O 3 PdO powder having a purity of 99.99% or more is a Pd-containing compound, is used as an additional element, and is then further purified at each mole of { Li 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 sb 0.04 )O 3 Mixed with 0.01 mole of PdO powder and the powder was wet mixed for 20 hours.
Similarly to example 1, a dense grain-oriented ceramic having a relative density of 95% or more was produced by adding a binder and a plasticizer, mixing the resultant slurry, molding, degreasing, and heating (firing). This is referred to as sample E9.
In sample E9, the additional element Pd was added from the surface in the form of Pd-containing compound PdO. Thus, the additional element Pd in sample E9 is present in the sample containing { Li 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 On the crystal grains or the crystal grain boundaries of the polycrystalline sintered body.
(example 10)
This example is an example of producing a grain-oriented ceramic whose main phase is comprised of { Li 0.04 (K 0.46 Na 0.54 ) 0.96 } (Nb 0.86 Ta 0.10 Sb 0.04 )O 3 And a Pd-containing polycrystalline sintered body.
In this example, similarly to example 3, flat plate-like NN powder, non-flat plate-like NN powder, KN powder, KT powder, and LS powder were prepared.
Mixing the raw materials in stoichiometric proportions to obtain the target composition, i.e., { Li 0.04 (K 0.46 Na 0.54 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 PdO powder having a purity of 99.99% or more, which is a Pd-containing compound, is used as an additional element, and then further purified at each mole of { Li } 0.04 (K 0.46 Na 0.54 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 And 0.01 mol of PdO powder, and the powders were wet-mixed for 20 hours.
Similarly to example 1, dense grain-oriented ceramics having a relative density of 95% or more were produced by adding a binder and a plasticizer, mixing the resultant slurry, molding, degreasing and heating (firing). This is referred to as sample E10.
In sample E10, the additional element Pd is surface-added in the form of a Pd-containing compound PdO. Therefore, the additional element Pd in sample E10 exists in the sample containing { Li 0.04 (K 0.46 Na 0.54 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 On the crystal grains or the crystal grain boundaries of the polycrystalline sintered body.
(example 11)
This example is an example of producing a grain-oriented ceramic whose main phase is Li including Mn added from the surface 0.75 (K 0.45 Na 0.55 ) 0.925 }(Nb 0.83 Ta 0.095 Sb 0.075 )O 3 The polycrystalline sintered body of (1).
A tabular NN powder was prepared in the same manner as in example 1.
Subsequently, na is mixed so as to contain predetermined amounts and to each contain 99.99% or more of purity 2 CO 3 Powder, a,K 2 CO 3 Powder, li 2 CO 3 Powder, nb 2 O 5 Powder, ta 2 O 5 Powder and Sb 2 O 5 Powder obtained (Li) 0.097 K 0.438 Na 0.483 )(Na 0.821 Ta 0.100 Sb 0.079 )O 3 ，MnO 2 Has a purity of99.99% or more, followed by MnO of Mn-containing compound 2 Used as an additional element and then further added at each mole of { Li 0.75 (K 0.45 Na 0.55 ) 0.925 }(Nb 0.83 Ta 0.095 Sb 0.075 )O 3 And 0.001 mol MnO 2 And (4) mixing. Thereafter, through a solid phase step, in a proportion (Li) to achieve the target composition 0.079 K 0.438 Na 0.483 )(Nb 0.821 Ta 0.100 Sb 0.079 )O 3 A predetermined amount of Mn was added thereto and mixed, the mixture prepared above was heated at 750 ℃ for 5 hours, and the reactant was pulverized with a ball mill.
Thereafter, the flat-plate-like NN powder and (Li) added to a predetermined amount of Mn 0.079 K 0.438 Na 0.483 )Nb 0.821 Ta 0.100 Sb 0.079 )O 3 The powder attains the target composition, i.e. results in Mn per mole { Li } 0.75 (K 0.45 Na 0.55 ) 0.925 } (Nb 0.83 Ta 0.095 Sb 0.075 )O 3 0.001 mol, and then the powder was wet-mixed for 20 hours.
Here, similarly to example 1, the flat plate-like NN powder (template) was mixed, and thus the amount of the additional element Na added accounted for the synthesis of { Li } NN powder provided from the starting material in a flat plate-like NN powder 0.75 (K 0.45 Na 0.55 ) 0.925 } (Nb 0.83 Ta 0.095 Sb 0.075 )O 3 The number of A positions in (C) is 5 atom%.
Similarly to example 1, dense grain-oriented ceramics having a relative density of 95% or more were produced by adding a binder and a plasticizer, mixing the resultant slurry, molding, degreasing and heating (firing). This is referred to as sample E11.
In sample E11, the additional element Mn is MnO with a purity of 99.99% 2 The powder, which is a Mn-containing compound, is added from the surface. Therefore, the additional element Mn in sample E11 exists in the composition containing { Li 0.75 (K 0.45 Na 0.55 ) 0.925 }(Nb 0.83 Ta 0.095 Sb 0.075 )O 3 Crystal grains or grain boundaries of the polycrystalline sintered body.
In this example, the Mn-containing compound for providing Mn as an additional element is MnO 2 But in addition to the compound MnO 2 In addition, mn metal, mnO, mn may be used 2 O 3 、Mn 2 O 4 ，Mn 3 O 4 And MnCO 3 。
To demonstrate the superior characteristics of the grain-oriented ceramics in examples 1-11, comparative ceramics (samples C1-C13) were made in comparative examples 1-13 below.
Comparative example 1
In the ceramics of this example, similarly to E1 and E2 produced in examples 1 and 2, the main phase is { Li } 0.03 (K 0.5 Na 0.5 ) 0.97 }(Nb 0.80 Ta 0.20 )O 3 ) The ceramics of this example was produced without using the flat plate-like NN powder (template) and without adding additional elements.
In this example, non-tabular NN powder, KN powder, and KT powder were mixed in a stoichiometric ratioEnd and LT powders to target composition, { Li 0.03 (K 0.5 Na 0.5 ) 0.97 }(Nb 0.80 Ta 0.20 )O 3 Then, wet mixing was performed for 20 hours.
Similar to example 1, a ceramic was produced by adding a binder and a plasticizer, mixing the resulting slurry, molding, degreasing, and heating (firing). This is referred to as sample C1.
That is, sample C1 was produced in the same manner as in E1 of example 1, except that the flat plate-like NN powder (template) was not used and no additional element was added.
Comparative example 2
In the ceramics of this example, similarly to E1 and E2 produced in examples 1 and 2, the main phase is { Li } 0.03 (K 0.5 Na 0.5 ) 0.97 }(Nb 0.80 Ta 0.20 )O 3 And containing Pd as an attached compoundAdding elements. The ceramics of this example was produced by not using the flat-plate NN powder (template).
In this example, non-tabular NN powder, KN powder, KT powder and LT powder were mixed in a stoichiometric ratio to obtain a target composition, { Li 0.03 (K 0.5 Na 0.5 ) 0.97 }(Nb 0.80 Ta 0.20 )O 3 PdO powder having a purity of 99.99% or more, which is a Pd-containing compound, is used as an additional element, and then further purified at each mole of { Li 0.03 (K 0.5 Na 0.5 ) 0.97 }(Nb 0.80 Ta 0.20 )O 3 And 0.01 mol of PdO powder, and the powder was wet-mixed for 20 hours.
Similarly to example 1, a ceramic was produced by adding a binder and a plasticizer, mixing the resultant slurry, molding, degreasing, and heating (firing). This is referred to as sample C2.
That is, the sample C2 was produced in the same manner as that used for E1 in example 1, except that the flat plate-like NN powder (template) was not used.
Comparative example 3
In the ceramic of the present example, similarly to E2 produced in example 2, the main phase was { Li } 0.03 (K 0.5 Na 0.5 ) 0.97 }(Nb 0.80 Ta 0.20 )O 3 Ni is contained as an additional element. The ceramics of this example was produced by not using the flat-plate NN powder (template).
In this example, non-tabular NN powder, KN powder, KT powder, and LT powder were mixed in a stoichiometric ratio to obtain a target composition, { Li 0.03 (K 0.5 Na 0.5 ) 0.97 }(Nb 0.80 Ta 0.20 )O 3 The NiO powder has a purity of 99.99% or more, which is a Ni-containing compound used as an additional element, and then further processed at each mole of { Li } 0.03 (K 0.5 Na 0.5 ) 0.97 }(Nb 0.80 Ta 0.20 )O 3 0.01 mol of NiO powder was added thereto and the mixture was wet-mixed for 20 hours.
Similar to example 1, a ceramic was produced by adding a binder and a plasticizer, mixing the resulting slurry, molding, degreasing, and heating (firing). This is referred to as sample C3.
That is, sample C3 was produced in the same manner as in E2 of example 2, except that the flat plate-like NN powder (template) was not used.
Comparative example 4
In the ceramics of this example, similarly to the samples E1 and E2, the main phase is one containing { Li 0.03 (K 0.5 Na 0.5 ) 0.97 } (Nb 0.80 Ta 0.20 )O 3 The polycrystalline sintered body of (4). The ceramic of this example contains no additional elements.
In this example, a flat NN powder, a non-flat NN powder, a KN powder, a KT powder, and an LT powder were mixed in a stoichiometric ratio to obtain a target composition, { Li 0.03 (K 0.5 Na 0.5 ) 0.97 }(Nb 0.80 Ta 0.20 )O 3 Then, wet mixing was performed for 20 hours.
Similarly to example 1, a ceramic was produced by adding a binder and a plasticizer, mixing the resultant slurry, molding, degreasing, and heating (firing). This is referred to as sample C4.
That is, sample C4 was produced in the same manner as in E1 of example 1, except that no additional element was mixed.
Comparative example 5
In the ceramics of this example, similarly to the samples E3 to E9 in examples 3 to 9, the main phase was a phase containing { Li 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 The polycrystalline sintered body of (4). The ceramics of this example were manufactured without using the flat plate-like NN powder (template) and without adding additional elements.
In this example, non-tabular NN powder, KN powder, KT powder, and LS powder were prepared.
In stoichiometric termsThe powders were mixed to obtain the target composition, { Li 0.04 (K 0.5 Na 0.5 ) 0.96 } (Nb 0.86 Ta 0.10 Sb 0.04 )O 3 Then, wet mixing was performed for 20 hours.
Similar to example 1, a ceramic was produced by adding a binder and a plasticizer, mixing the resulting slurry, molding, degreasing, and heating (firing). This is referred to as sample C5.
That is, the sample C5 was produced in the same manner as the samples E3 to E9 except that the additional elements were not mixed and the flat NN powder was not used.
Comparative example 6
In the ceramic of this example, similarly to the sample E3 in example 3, the main phase was a phase containing { Li 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 And an In-containing polycrystalline sintered body. The ceramics of this example was produced without using flat plate-like NN powder (template).
In this example, non-tabular NN powder, KN powder, KT powder and LT powder were prepared.
These powders were mixed in stoichiometric proportions to give the target composition, i.e. { Li } 0.04 (K 0.5 Na 0.5 ) 0.96 } (Nb 0.86 Ta 0.10 Sb 0.04 )O 3 ，In 2 O 3 The powder has a purity of 99.99% or more and is an In-containing compoundIs used as an additional element and then further added at each mole of { Li 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 And 0.005 mol of In 2 O 3 The powders were mixed and wet-mixed for 20 hours.
Similarly to example 1, a ceramic was produced by adding a binder and a plasticizer, mixing the resultant slurry, molding, degreasing, and heating (firing). This is referred to as sample C6.
That is, the same method as used for the sample E3 was used except that the flat NN powder was not used for the sample C6.
Comparative example 7
In the ceramic of this example, similarly to the sample E4 in example 4, the main phase thereof was { Li ] including Ca added for replacing part of K and Na 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 The polycrystalline sintered body of (1). The ceramics of this example was produced without using the flat plate-like NN powder (template).
In this example, non-tabular NN powder, KN powder, KT powder, and LS powder were prepared. Likewise, caCO prepared 3 The powder has a purity of 99.99% or more, which is a Ca-containing compound as an additional element.
Mixing the raw materials in a stoichiometric ratio to obtain { Li 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 With addition of Ca to replace part of K and Na to give { Li 0.04 (K 0.5 Na 0.5 ) 0.94 Ca 0.10 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 Then, wet mixing was performed for 20 hours.
Similarly to example 1, a ceramic was produced by adding a binder and a plasticizer, mixing the resultant slurry, molding, degreasing, and heating (firing). This is referred to as sample C7.
That is, the same method as used for the sample E4 was used except that the flat NN powder was not used for the sample C7.
Comparative example 8
In the ceramic of the present example, similarly to the sample E5 in example 5, the main phase is a phase containing { Li [ ] 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 And a polycrystalline sintered body containing Si. The ceramics of this example was manufactured without using flat-plate-like NN powder (a template).
In this example, non-tabular NN powder, KN powder, KT powder, and LS powder were prepared.
Mixing the raw materials in stoichiometric proportions to obtain the target composition, i.e., { Li 0.04 (K 0.5 Na 0.5 ) 0.96 } (Nb 0.86 Ta 0.10 Sb 0.04 )O 3 ，SiO 2 The powder has a purity of 99.99% or more, which is a Si-containing compound used as an additional element, and then further purified at every mole of { Li } 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 And 0.01 mol SiO 2 The powders were mixed and wet-mixed for 20 hours.
Similarly to example 1, a ceramic was produced by adding a binder and a plasticizer, mixing the resultant slurry, molding, degreasing, and heating (firing). This is referred to as sample C8.
That is, the same method as used for the sample E5 was used to manufacture the sample C8, except that the flat NN powder was not used.
Comparative example 9
In the ceramic of this example, similarly to the sample E6 in example 6, the main phase was a phase containing { Li 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 And a polycrystalline sintered body containing Ag. The ceramics of this example were manufactured without using the flat-plate-like NN powder (template).
In this example, non-tabular NN powder, KN powder, KT powder, and LS powder were prepared.
Mixing the raw materials in stoichiometric proportions to obtain the target composition, i.e., { Li 0.04 (K 0.5 Na 0.5 ) 0.96 } (Nb 0.86 Ta 0.10 Sb 0.04 )O 3 ，Ag 2 O powder having a purity of 99.99% or more, which is a compound containing Ag, is used as an additional element, and then further per mol { Li } 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 And 0.005 mol Ag 2 O powder was mixed, and the powder was wet-mixed for 20 hours.
Similarly to example 1, a ceramic was produced by adding a binder and a plasticizer, mixing the resultant slurry, molding, degreasing, and heating (firing). This is referred to as sample C9.
That is, the same method as that used for the sample E6 was used except that the flat plate-like NN powder was not used for the sample C9.
Comparative example 10
In the ceramics of this example, similarly to the sample E8 in example 8, the main phase is { Li ] including Sr added for replacing part of K and Na 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 The polycrystalline sintered body of (4). The ceramics of this example were manufactured without using the flat-plate-like NN powder (template).
In this example, non-tabular NN powder, KN powder, KT powder, and LS powder were prepared similarly to example 3. SrCO prepared in the same way 3 The powder has a purity of 99.99% or more, which is an Sr-containing compound as an additional element.
Mixing the raw materials in stoichiometric ratio to obtain { Li 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 With addition of Sr to replace part of K and Na to give { Li 0.04 (K 0.5 Na 0.5 ) 0.94 Sr 0.01 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 Then, wet mixing was performed for 20 hours.
Similar to example 1, a ceramic was produced by adding a binder and a plasticizer, mixing the resulting slurry, molding, degreasing, and heating (firing). This is referred to as sample C10.
That is, the same method as that used for the sample E8 was used except that the flat plate-like NN powder was not used for the sample C10.
Comparative example 11
In the ceramic of the present example, similarly to the sample E9 in example 9, the main phase was made to contain { Li [ ] 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 And contains Pd. The ceramics of this example was manufactured without using flat-plate-like NN powder (a template).
In this example, non-tabular NN powder, KN powder, KT powder, and LS powder were prepared.
Mixing the raw materials in stoichiometric proportions to obtain the target composition, i.e., { Li 0.04 (K 0.5 Na 0.5 ) 0.96 } (Nb 0.86 Ta 0.10 Sb 0.04 )O 3 PdO powder having a purity of 99.99% or more, which is a Pd-containing compound, is used as an additional element, and then further purified at each mole of { Li 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 And 0.01 mol of PdO powder, and the powders were wet-mixed for 20 hours.
Similarly to example 1, a ceramic was produced by adding a binder and a plasticizer, mixing the resultant slurry, molding, degreasing, and heating (firing). This is referred to as sample C11.
That is, the same method as used for the sample E9 was used to manufacture the sample C11, except that the flat NN powder was not used.
Comparative example 12
In the ceramics of this example, similarly to the samples E3 to E9 in examples 3 to 9, the main phase was a phase containing { Li 0.04 (K 0.5 Na 0.5 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 The polycrystalline sintered body of (1). The ceramic of this example was made without the addition of additional elements.
In this example, similarly to example 3, a tabular NN powder, a non-tabular NN powder, a KN powder, a KT powder, and a LS powder were prepared.
These powders were mixed in stoichiometric proportions to give the target composition, { L }i 0.04 (K 0.5 Na 0.5 ) 0.96 } (Nb 0.86 Ta 0.10 Sb 0.04 )O 3 Then, wet mixing was performed for 20 hours.
Similarly to example 1, a ceramic was produced by adding a binder and a plasticizer, mixing the resultant slurry, molding, degreasing, and heating (firing). This is referred to as sample C12.
That is, the method used to manufacture sample C12 was the same as that used to manufacture samples E3-E9, except that no additional elements were mixed.
Comparative example 13
In the ceramic of this example, similarly to the sample E11 in example 11, the main phase was a phase containing { Li 0.75 (K 0.45 Na 0.55 ) 0.925 }(Nb 0.83 Ta 0.095 Sb 0.075 )O 3 The polycrystalline sintered body of (1). The ceramic of this example was made without the addition of additional elements.
In this example, a tabular NN powder was prepared similarly to example 1.
Subsequently, na containing a predetermined amount and each having a purity of 99.99% or more is mixed 2 CO 3 Powder, K 2 CO 3 Powder, li 2 CO 3 Powder, nb 2 O 5 Powder, ta 2 O 5 Powder and Sb 2 O 5 The powder is produced in a solid phase reaction step (Li) 0.079 K 0.438 Na 0.483 )(Nb 0.821 Ta 0.100 Sb 0.079 )O 3 The mixture was heated at 750 ℃ for 5 hours, and the reaction mixture was pulverized by a ball mill.
Thereafter, flat NN powders and (Li) were mixed in a stoichiometric ratio 0.079 K 0.438 Na 0.483 ) (Nb 0.821 Ta 0.100 Sb 0.079 )O 3 The powder obtained the target composition, i.e., { Li 0.75 (K 0.45 Na 0.55 ) 0.925 }(Nb 0.83 Ta 0.095 Sb 0.075 )O 3 Then wet-mixing for 20 hoursAnd (6) mixing.
Here, similarly to example 1, the flat plate-like NN powder (template) was mixed, and thus the amount of the additional element Na added accounted for the synthesis of { Li } NN powder provided from the starting material in a flat plate-like NN powder 0.75 (K 0.45 Na 0.55 ) 0.925 } (Nb 0.83 Ta 0.095 Sb 0.075 )O 3 The number of A positions in (C) is 5 atom%.
Similarly to example 1, grain-oriented ceramics having a relative density of 95% or more were produced by adding a binder and a plasticizer, mixing the resultant slurry, molding, degreasing and heating (firing). This refers to sample C13.
Thus, sample C13 was made in the same manner as sample E11, except that no additional elements were mixed.
(test example)
In this example, samples E1-E10 and sample C2 were subjected to X-ray diffraction measurements. FIGS. 1-11 are shown for measuring parallel X-ray diffraction patterns of each sample face and the tape casting face.
As can be seen from fig. 1 to 11, the pseudo-cubic {100} planes in the samples E1 to E10 produced using the flat NN powder as the template were oriented to a significantly high degree of orientation as compared with the sample C2.
Then, the following are evaluations of the degree of orientation of {100} planes and the piezoelectric characteristics of the samples E1 to E10 and the samples C1 to C12 produced in comparative examples 1 to 10 and comparative examples 1 to 12.
[ degree of orientation ]
The average orientation F (100) of the {100} plane of the face of each polycrystalline sintered sample and the strand casting face was measured by the Lotgering method. The average degree of orientation F (100) is calculated according to mathematical formula 1. The results obtained are represented in tables 1 and 2 below.
[ piezoelectric characteristics ]
Measuring the piezoelectric characteristics, piezoelectric d, of samples E1-E10 and C1-C12 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 A constant.
As for the measurement method, a disk-shaped sample having a thickness of 0.7 mm and a diameter of 11 mm was prepared from the polycrystalline sintered sample obtained by grinding, lapping and processing, with the upper and lower surfaces being parallel to the band-shaped casting surface. The upper and lower surfaces of the disc-shaped sample were sprayed with Au electrodes, and then the piezoelectric characteristics were measured at room temperature by the resonance-antiresonance method using a polarization step in the vertical direction of the disc-shaped sample under the condition that the electric field intensity was 1V/mm. The results obtained are represented in tables 1 and 2 below.
Similarly, the piezoelectric characteristics of the samples E11 and C13 were measured as follows.
Polycrystalline sintered samples prepared from samples E11 and C13 were disc-shaped samples having upper and lower surfaces parallel to the band-shaped casting surface and a thickness of 0.485 mm and a diameter of 8.5 mm by grinding, milling, and processing. Subsequently, the upper and lower surfaces of the disc-shaped sample were sprayed with Au electrode paste (ALP 3057, manufactured by sumitomo sequin metal mine mining limited company), and then baked at 850 ℃ for 10 minutes using a mesh belt type oven to obtain an electrode having a thickness of 0.01 mm. After using the polarization step in the vertical direction of the disc-shaped sample, the piezoelectric d as a piezoelectric property was measured at room temperature by the resonance-antiresonance method under the condition that the electric field intensity was 1V/mm 31 Constant, electromechanical coupling coefficient Kp, piezoelectric g 31 Constant and dielectric loss tan delta.
In the measurement of the dielectric loss tan δ, the dielectric loss tan δ is measured by detecting the temperature dependence of the dielectric loss tan δ by changing the temperature.
As to samples E11 and C13, piezoelectric d 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 The results of the constants are represented in tables 1 and 2 below, and the results of the dielectric loss tan δ are represented in fig. 12.
(Table 1)
| Sample number | Components | Number of templates (original) Sub%) | With or without Degree of orientation | Degree of orientation (%) | d 31 (pm/V) | Kp | g 31 (×10 -3 Vm/N) | ||||
| x | y | z | w | Additional elements | |||||||
| Species of | |||||||||||
| Sample E1 | 0.03 | 0.5 | 0.2 | 0 | Pd | 5 | Is provided with | 93 | 133 | 0.685 | 21.3 |
| Sample E2 | 0.03 | 0.5 | 0.2 | 0 | Ni | 5 | Is provided with | 96 | 104 | 0.620 | 21.0 |
| Sample E3 | 0.04 | 0.5 | 0.1 | 0.04 | In | 5 | Is provided with | 96 | 137 | 0.713 | 21.2 |
| Sample E4 | 0.04 | 0.5 | 0.1 | 0.04 | Ca | 5 | Is provided with | 91 | 136 | 0.586 | 10.5 |
| Sample E5 | 0.04 | 0.5 | 0.1 | 0.04 | Si | 5 | Is provided with | 92 | 128 | 0.593 | 13.2 |
| Sample E6 | 0.04 | 0.5 | 0.1 | 0.04 | Ag | 5 | Is provided with | 98 | 149 | 0.707 | 21.4 |
| Sample E7 | 0.04 | 0.5 | 0.1 | 0.04 | Ag | 5 | Is provided with | 93 | 132 | 0.586 | 12.0 |
| Sample E8 | 0.04 | 0.5 | 0.1 | 0.04 | Sr | 5 | Is provided with | 78 | 113 | 0.531 | 808 |
| Sample E9 | 0.04 | 0.5 | 0.1 | 0.04 | Pd | 5 | Is provided with | 92 | 142 | 0.633 | 13.2 |
| Sample E10 | 0.04 | 0.54 | 0.1 | 0.04 | Pd | 5 | Is provided with | 97 | 151 | 0.683 | 17.9 |
| Sample E11 | 0.075 | 0.55 | 0.095 | 0.075 | Mm | 5 | Is provided with | 93 | 87 | 0.519 | 9.8 |
(Table 2)
| Sample number | Components | Number of templates (original) Seed%) | With or without Degree of orientation | Degree of orientation (%) | d 31 (pm/V) | Kp | g 31 (×10 -3 Vm/N | ||||
| x | y | z | w | Additional elements | |||||||
| Species of | |||||||||||
| Sample C1 | 0.03 | 0.5 | 0.2 | 0 | - | 0 | Is not provided with | 0 | 100 | 0.505 | 9.0 |
| Sample C2 | 0.03 | 0.5 | 0.2 | 0 | Pd | 0 | Is not provided with | 0 | 106 | 0.520 | 9.0 |
| Sample C3 | 0.03 | 0.5 | 0.2 | 0 | Ni | 0 | Is not provided with | 0 | 94 | 0.470 | 7.8 |
| Sample C4 | 0.03 | 0.5 | 0.2 | 0 | - | 5 | Is provided with | 95 | 126 | 0.618 | 17.1 |
| Sample C5 | 0.04 | 0.5 | 0.1 | 0.04 | - | 0 | Is not provided with | 0 | 96 | 0.452 | 7.8 |
| Sample C6 | 0.04 | 0.5 | 0.1 | 0.04 | In | 0 | Is not provided with | 0 | 106 | 0.498 | 8.5 |
| Sample C7 | 0.04 | 0.5 | 0.1 | 0.04 | Ca | 0 | Is not provided with | 0 | 106 | 0.484 | 7.6 |
| Sample C8 | 0.04 | 0.5 | 0.1 | 0.04 | Si | 0 | Is not provided with | 0 | 97 | 0.470 | 8.0 |
| Sample C9 | 0.04 | 0.5 | 0.1 | 0.04 | Ag | 0 | Is not provided with | 0 | 99 | 0.466 | 7.6 |
| Sample C10 | 0.04 | 0.5 | 0.1 | 0.04 | Sr | 0 | Is not provided with | 0 | 102 | 0.480 | 7.6 |
| Sample C11 | 0.04 | 0.5 | 0.1 | 0.04 | Pd | 0 | Is not provided with | 0 | 112 | 0.531 | 8.7 |
| Sample C12 | 0.04 | 0.5 | 0.1 | 0.04 | - | 5 | Is provided with | 94 | 113 | 0.554 | 13.9 |
| Sample C13 | 0.075 | 0.55 | 0.095 | 0.075 | - | 5 | Is provided with | 83 | 81 | 0.449 | 7.7 |
As can be seen from Table 1, in the grain-oriented ceramics of samples E1 to E10, the pseudo-cubic {100} planes are oriented parallel to the band-shaped planes. As for the average degree of orientation of the cubic {100} plane, it shows a high degree of orientation of 78% or more according to the Lotgering methodAnd (4) direction and degree. Also, the samples E1 to E10 exhibited excellent piezoelectric characteristics because of the piezoelectric d 31 A constant of 104pm/V or more, an electromechanical coupling coefficient Kp of 0.531 or more, and a piezoelectric g 31 Constant is 8.8X 10 -3 Vm/N or more.
Furthermore, as can be seen from tables 1 and 2, in sample E1, the piezoelectric d is higher than that of sample C1 having the same composition but no orientation and no additional element added thereto 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 The constants were increased by a factor of 1.33, 1.36 and 2.37, respectively. In sample E1, the piezoelectric d is compared with that of sample C2 which has the same composition and added additional element Pd but has no orientation 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 The constants were increased by a factor of 1.25, 1.32 and 2.36, respectively. Furthermore, in sample E1, the piezoelectric d is compared with that of sample C4 having the same composition and orientation but without the addition of additional elements 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 The constants were increased by 1.06 times, 1.11 times and 1.25 times, respectively.
In sample E2, the piezoelectric d is compared with that of sample C1 which has the same composition but has no orientation and also has no additional element added 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 The constants were increased by a factor of 1.04, 1.23 and 2.33, respectively. Meanwhile, in sample E2, the pressure d is higher than that of sample C3 containing the same composition and added additional element Ni but having no orientation 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 The constants were increased by a factor of 1.11, 1.32 and 2.69, respectively.
In sample E3, the piezoelectric d is compared with that of sample C5 which has the same composition but has no orientation and also has no additional element added 31 Constant, electromechanical coupling diaphragm coefficient Kp and piezoelectric g 31 The constants were increased by a factor of 1.43, 1.58 and 2.72, respectively. Also, in sample E3, the pressure d is higher than that of sample C6 containing the same composition and added additional element In but having no orientation 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 The constants were increased by a factor of 1.29, 1.43 and 2.50, respectively. In addition, the method can be used for producing a composite materialIn sample E3, the piezoelectric d is compared with that of sample C12 having the same composition and orientation but no additional element added 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 The constants were increased by 1.21 times, 1.29 times, and 1.53 times, respectively.
In sample E4, the piezoelectric d is compared with that of sample C5 which has the same composition but has no orientation and also has no additional element added 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 The constants were increased by 1.42 times, 1.30 times and 1.35 times, respectively. Also, in sample E3, the piezoelectric d is compared with that of sample C7 containing the same composition and added additional element Ca but having no orientation 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 The constant is increased to 1.28 times, 1.21 times and 1.37 times respectively.
In sample E5, the piezoelectric d is compared with that of sample C5 which has the same composition but no orientation and no additional element added 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 The constants were increased by a factor of 1.33, 1.31 and 1.69, respectively. Also, in sample E5, the piezoelectric d is compared with that of sample C8 containing the same composition and added additional element Si but having no orientation 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 The constants were increased by a factor of 1.33, 1.26 and 1.65, respectively.
In sample E6, the piezoelectric d is compared with that of sample C5 which has the same composition but no orientation and no additional element added 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 The constants were increased by a factor of 1.55, 1.56 and 2.74, respectively. Also, in sample E6, the piezoelectric d is compared with that of sample C9 containing the same composition and added additional element Ag but having no orientation 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 The constants were increased by a factor of 1.50, 1.52 and 2.81, respectively.
Further, in sample E6, the piezoelectric d is compared with that of sample E7 containing the same composition and added with the same additional element Ag but having a different degree of orientation 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 The constants were increased by 1.13 times, 1.21 times, and 1.78 times, respectively.
In sample E7, the piezoelectric d is compared with that of sample C5 which has the same composition but has no orientation and also has no additional element added 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 The constants were increased by a factor of 1.38, 1.30 and 1.54, respectively. Also, in sample E7, the piezoelectric d is compared with that of sample C9 having the same composition and added additional element Ag but having no orientation 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 The constants were increased by a factor of 1.33, 1.26 and 1.57, respectively.
In sample E8, the piezoelectric d is compared with that of sample C5 which has the same composition but no orientation and no additional element added 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 The constants were increased to 1.18 times, 1.17 times, and 1.13 times, respectively. Also, in sample E8, the piezoelectric d is compared with that of sample C10 containing the same composition and added additional element Sr but having no orientation 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 The constants were increased by 1.11 times, 1.11 times and 1.16 times, respectively.
In sample E9, the piezoelectric d is compared with that of sample C5 which has the same composition but no orientation and no additional element added 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 The constants were increased by a factor of 1.48, 1.40 and 1.69, respectively. Also, in sample E9, the piezoelectric d is compared with that of sample C11 containing the same composition and added additional element Pd but having no orientation 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 The constants were increased to 1.26 times, 1.19 times and 1.51 times, respectively.
Example E10 contains { Li 0.04 (K 0.46 Na 0.54 ) 0.96 }(Nb 0.86 Ta 0.10 Sb 0.04 )O 3 And neutralizing the grain-oriented ceramic containing the additional element Pd. The ratio of the elements K/Na in the A position in sample E10 to that in sample E9 is 1: 1In contrast, its piezoelectric d 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 Constant is respectively providedUp to 1.07 times, 1.08 times and 1.35 times.
In sample E11, the piezoelectric d is compared with that of sample C13 having the same composition and orientation but no additional element added 31 Constant, electromechanical coupling coefficient Kp and piezoelectric g 31 The constants were increased by a factor of 1.08, 1.16 and 128, respectively. Also, as can be seen from fig. 12, in sample E11, the dielectric loss tan δ has a small absolute value and less fluctuation due to the representative temperature as compared to sample C13, which improves the temperature dependence of tan δ.
Thus, it was confirmed that in samples E1 to E11, the piezoelectric characteristics could be improved by the particular crystal plane orientation and the addition of the additional element.
The embodiments of the present invention are described in detail through the foregoing pages, but the present invention is not limited thereto. Various modifications and changes can be made without departing from the gist of the present invention.
For example, in the above-described embodiment, when one element is added, the objective element may be added by using an oxide, but a metal containing the element, an oxide, for example, a carbonate, a nitrate, a metal alkoxide, or the like, having a different valence from that in the embodiment may be used.
Claims (20)
1. A grain-oriented ceramic comprising formula (1) as a major phase: { Li x (K 1-y Na y ) 1-x }(Nb 1-z-w Ta z Sb w )O 3 (wherein each of x, y, z and w is in the composition range of 0. Ltoreq. X.ltoreq.0.2, 0. Ltoreq. Y.ltoreq.1, 0. Ltoreq. Z.ltoreq.0.4, 0. Ltoreq. W.ltoreq.0.2, and x + z + w > 0),
wherein
The main phase includes a polycrystal containing 0.0001 to 0.15 mol of any one or more additional elements selected from metal elements belonging to groups 2 to 15 of the periodic Table, semimetal elements, transition metal elements, noble metal elements and alkaline earth metal elements per 1 mol of the compound represented by the formula (1), and
specific crystal planes of crystal grains constituting the polycrystalline body are oriented.
2. The grain-oriented ceramic according to claim 1, wherein the additional element is contained in grains constituting the polycrystalline body and/or on a grain boundary.
3. The grain-oriented ceramic according to claim 1, wherein the additional element is added at a ratio of 0.01 to 15 atomic% in place of any one or more elements selected from the group consisting of Li, K, na, nb, ta and Sb in the isotropic perovskite-type compound represented by formula (1).
4. The grain oriented ceramic of claim 1, wherein the additional element is any one or more elements selected from the group consisting of Mg, ca, sr and Ba.
5. The grain oriented ceramic of claim 1, wherein the additional element is any one or more elements selected from the group consisting of Sc, ti, V, cr, mn, fe, co, ni, cu, zn, Y, zr, mo, hf, W, and Re.
6. The grain oriented ceramic of claim 1, wherein the additional element is any one or more elements selected from the group consisting of Pd, ag, ru, rh, pt, au, ir, and Os.
7. The grain oriented ceramic of claim 1, wherein the additional element is any one or more elements selected from the group consisting of B, al, ga, in, si, ge, sn and Bi.
8. The grain-oriented ceramic according to claim 1, wherein the degree of orientation of pseudo-cubic {100} planes in the polycrystal measured by a rockwell method is 30% or more.
9. The grain oriented ceramic of claim 1, wherein the grain oriented ceramic has a piezoelectric d 31 Piezoelectric d of non-oriented ceramic having a constant of a polycrystalline body of the same composition as that of the grain-oriented ceramic and in which crystal planes of crystal grains constituting the polycrystalline body are not oriented 31 1.1 times or more of the constant.
10. The grain-oriented ceramic according to claim 1, wherein the grain-oriented ceramic has an electromechanical coupling coefficient Kp that is 1.1 times or more the piezoelectric electromechanical coupling coefficient Kp of a non-oriented ceramic in which crystal planes constituting the crystal grains of the polycrystal do not have orientation.
11. The grain oriented ceramic of claim 1, wherein the grain oriented ceramic has a piezoelectric g 31 A piezoelectric g constant of a non-oriented ceramic which contains a polycrystal of the same composition as the grain-oriented ceramic and in which crystal planes of crystal grains constituting the polycrystal are not oriented 31 1.1 times or more of constant
12. A piezoelectric element comprising a piezoelectric material containing the grain-oriented ceramic described in any one of claims 1 to 11.
13. A dielectric element comprising a dielectric material comprising the grain-oriented ceramic as claimed in any one of claims 1 to 11.
14. A thermoelectric conversion element comprising a thermoelectric conversion material comprising the grain-oriented ceramic as set forth in any one of claims 1 to 11.
15. An ion conducting component comprising an ion conducting material comprising the grain oriented ceramic of any one of claims 1-11.
16. A method of making a grain-oriented ceramic, comprising:
a mixing step of mixing (i) a first anisotropically shaped powder comprising oriented fine particles having oriented planes in which specific crystal planes are oriented, and (ii) reacting with the first anisotropically shaped powder to produce { Li } formula (1) x (K 1-y Na y ) 1-x }(Nb 1-z-w Ta z Sb w )O 3 (wherein 0. Ltoreq. X.ltoreq.0.2, 0. Ltoreq. Y.ltoreq.1, 0. Ltoreq. Z.ltoreq.0.4, 0. Ltoreq. W.ltoreq.0.2 and x + z + w > 0), and (iii) any one or more additional elements selected from metal elements belonging to groups 2 to 15 of the periodic Table of the elements, semimetal elements, transition metal elements, noble metal elements and alkaline earth metal elements, thereby producing a raw material mixture,
a molding step of molding the raw material mixture so that the orientation planes of the first anisotropically shaped powder are oriented in almost the same direction in a molded body, and
a heat treatment step of heating the molded body to react the first anisotropically shaped powder with a first reaction raw material, thereby producing a polycrystal which contains an isotropic perovskite-type compound represented by formula (1) and whose crystal grains are oriented and exhibit a texture structure,
wherein
In the mixing step, the additional element is added in an amount of 0.0001 to 0.15 mol per mol of the compound represented by formula (1), and
the oriented planes of the oriented fine particles have a lattice matching with specific planes in the crystal grains constituting the polycrystalline body obtained in the heat treatment step.
17. The method of manufacturing a grain-oriented ceramic according to claim 16, wherein the oriented fine particles have a tabular morphology.
18. The method of making a grain-oriented ceramic according to claim 16, wherein the oriented microparticles comprise formula (2): { Li x (K 1-y Na y ) 1-x }(Nb 1-z-w Ta z Sb w )O 3 Wherein x is 0. Ltoreq. X.ltoreq.1, y is 0. Ltoreq. Y.ltoreq.1, z is 0. Ltoreq. Z.ltoreq.1, and w is 0. Ltoreq. W.ltoreq.1.
19. The method of producing a grain-oriented ceramic according to claim 16, wherein the orientation plane of the oriented fine grains is a pseudo-cubic {100} plane.
20. The method of producing a grain-oriented ceramic according to claim 16, wherein the additional element is one or more elements selected from the group consisting of Mg, ca, sr, ba, sc, ti, V, cr, mn, fe, co, ni, cu, zn, Y, zr, mo, ru, rh, pd, ag, hf, W, re, pt, au, ir, os, B, al, ga, in, si, ge, sn, and Bi.
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