JP2013155079A - Piezoelectric ceramic composition and piezoelectric element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric ceramic composition comprising a non-lead material and having little deterioration of polarization even at a high temperature, and to provide a piezoelectric element containing the piezoelectric ceramic composition having little deterioration of characteristic even at a high temperature.SOLUTION: A piezoelectric ceramic composition includes at least three components, namely, bismuth sodium titanate, bismuth potassium titanate and barium dititanate, as main components, and as for the composition ratio thereof aBNT-bBKT-cBT2, the composition range of (a, b, c) is in a domain (including lines connecting each point) enclosed by A (0.61, 0.38, 0.01), B (0.41, 0.58, 0.01), C (0.51, 0.38, 0.11) and D (0.31, 0.58, 0.11) on a composition diagram of the three components.

Description

  The present invention relates to a piezoelectric ceramic composition and a piezoelectric element that are widely used in the fields of actuators, sensors, and resonators.

Most of the piezoelectric ceramic compositions that are currently in practical use are solid solution systems (PZT systems) composed of PbZrO ₃ (PZ) -PbTiO ₃ (PT). The reason is that excellent piezoelectric characteristics can be obtained by using a composition near the crystallographic phase boundary (MPB) of rhombohedral PZ and tetragonal PT. is there. A wide variety of PZT piezoelectric materials have been developed that meet various needs by adding various subcomponents or additives. In addition to PZT materials, there are materials that have been put to practical use as piezoelectric materials, but they also have lead-based perovskite compositions such as lead magnesium niobate (Pb (Mg, Nb) O ₃ : PMN) as the main component. Most are solid solutions.

  However, these lead-based piezoelectric materials contain a large amount of lead oxide (PbO) having a very high volatility at a low temperature of about 60 to 70% by mass as a main component. For example, in PZT or PMN, about 2/3 by mass is lead oxide. Therefore, when manufacturing these piezoelectric materials, an extremely large amount of lead oxide is volatilized and diffused in the atmosphere at an industrial level in a heat treatment process such as a firing process for porcelain and a melting process for single crystal products. End up. In addition, it is possible to recover the lead oxide released in the manufacturing stage. However, it is difficult to recover the lead oxide contained in the piezoelectric products put on the market as industrial products. When released to the sea, there is a concern about lead elution due to acid rain. Accordingly, if the application fields of piezoelectric ceramics and single crystals are expanded in the future, and the amount of use increases, the problem of lead-free becomes a very important issue.

Currently, (Bi _0.5 Na _0.5 ) TiO ₃ (bismuth sodium titanate, hereinafter referred to as “BNT”) is known as a lead-free piezoelectric ceramic. BNT is a perovskite-type piezoelectric ceramic similar to PZT and has a relatively high electromagnetic coupling coefficient.

Various improved composition systems have been investigated based on this BNT. BaTiO ₃ (barium titanate; hereinafter referred to as “BT”) and (Bi _0.5 K _0.5 ) TiO ₃ (bismuth potassium titanate; hereinafter referred to as “BKT”) are dissolved in BNT. A piezoelectric ceramic composition made is disclosed in Patent Document 1.

JP 2001-151666 A

Known piezoelectric ceramic compositions that do not contain lead include, for example, barium titanate (BaTiO ₃ ) and bismuth layered ferroelectrics. However, barium titanate has a low Curie point of 130 ° C., and the piezoelectricity disappears above that temperature. On the other hand, a bismuth layered ferroelectric usually has a Curie point of 400 ° C. or higher and is excellent in thermal stability, but has a large crystal anisotropy, so that polarization is difficult and productivity is high. There is a problem.

  Furthermore, recently, research has been conducted on a bismuth sodium titanate-based material as a new material. However, these bismuth sodium titanate-based materials have not yet obtained sufficient piezoelectric characteristics as compared with lead-based piezoelectric materials, and further improvements in piezoelectric characteristics have been demanded.

  The present invention has been made in view of the above, and an object of the present invention is to provide a piezoelectric ceramic composition that is a lead-free material and has little deterioration in polarization even at high temperatures. In addition, the present invention provides a piezoelectric element including a piezoelectric ceramic composition with little deterioration in characteristics even at high temperatures.

  In order to achieve the above object, the present inventors have studied various piezoelectric material compositions. And the composition of the piezoelectric ceramic composition which is a lead-free material and has little deterioration in polarization even at a high temperature was found.

  The piezoelectric ceramic composition of the present invention has a molar ratio of bismuth sodium titanate, potassium bismuth titanate and barium dititanate as a: b: c (bismuth sodium titanate: bismuth potassium titanate: barium dititanate = a: b: c), the composition range of (a, b, c) is A (0.61, 0.38, 0.01), B (0.41, 0. 58, 0.01), C (0.51, 0.38, 0.11), and D (0.31, 0.58, 0.11) in the region (including the line connecting the points). ).

  The three components are bismuth sodium titanate (hereinafter BNT) having a Curie temperature of 320 ° C., bismuth potassium titanate (hereinafter BKT) having a Curie temperature of 380 ° C., and barium dititanate (hereinafter BT 2) having a Curie temperature of 479 ° C., both of which are made of a material having a high Curie temperature of 300 ° C. or higher. The dielectric constant of the piezoelectric body increases as the temperature rises. As a result, the crystal becomes unstable, and the crystal system suddenly changes at a certain temperature. This temperature is the Curie temperature and represents the critical temperature at which the polarization disappears, and at this temperature the piezoelectricity is lost. When a component having a high Curie temperature is used, the deterioration of polarization is suppressed to a high temperature, and an excellent effect is obtained. Furthermore, by using a plurality of components having different crystal systems, it becomes possible to obtain piezoelectric characteristics higher than those of a single component.

Further, the general chemical formulas of the three components of the piezoelectric ceramic composition of the present invention are as follows: sodium bismuth titanate (Bi _0.5 Na _0.5 ) _d TiO ₃ and potassium bismuth titanate (Bi _0.5 K _0.5 ). _{When e} TiO ₃ and barium dititanate are Ba _f Ti ₂ O ₅ , d is 0.9 ≦ d ≦ 1.0, e is 0.9 ≦ e ≦ 1.0, and f is 0.9 ≦ f. It is preferable that ≦ 1.1.

  Here, when d is 0.9 ≦ d ≦ 1.0, e is 0.9 ≦ e ≦ 1.0, and f is 0.9 ≦ f ≦ 1.1, the sinterability is further improved. Is possible.

  Moreover, in this invention, the piezoelectric element containing said piezoelectric ceramic composition is provided. Since such a piezoelectric element includes the piezoelectric ceramic composition having the above characteristics, excellent performance can be obtained even when used in a high temperature environment.

  In order to solve the above-described problems and achieve the object, according to the present invention, it is possible to provide a piezoelectric ceramic composition that is a lead-free material and has little deterioration in piezoelectric characteristics even at high temperatures. In addition, by including such a piezoelectric ceramic composition, it is possible to provide a piezoelectric element with little deterioration in piezoelectric characteristics.

It is a ternary composition diagram showing a preferred composition of the piezoelectric ceramic composition according to the present invention. It is a perspective view showing the example of 1 structure of the piezoelectric element using the piezoelectric ceramic composition which concerns on one Embodiment of this invention. It is sectional drawing showing another structural example of the piezoelectric element using the piezoelectric ceramic composition which concerns on one Embodiment of this invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

(Embodiment 1)
The piezoelectric ceramic composition according to the embodiment of the present invention is characterized by having at least three components of BNT, BKT, and BT2 as main components. Here, a solid solution containing BNT, BKT, and BT2 is contained. That is, three kinds of compounds are included, and they may be dissolved. Furthermore, it is preferable that at least BT2 remains without completely dissolving, in order to maintain a high Curie temperature.

BNT has a rhombohedral perovskite structure ABO ₃ , sodium and bismuth are located at the A site of the perovskite structure, and titanium is located at the B site of the perovskite structure.

BNT is represented by the general chemical formula (Bi _0.5 Na _0.5 ) _d TiO ₃ . In this formula, d is 1 if it is a stoichiometric composition, but it may deviate from the stoichiometric composition, and if it is 0.9 or more and 1 or less, the sinterability can be improved and higher. It is preferable because piezoelectric characteristics can be obtained. The composition of sodium and bismuth and the composition of oxygen are determined from the stoichiometric composition and may deviate from the stoichiometric composition.

BKT is represented by the general chemical formula (Bi _0.5 K _0.5 ) _e TiO ₃ . In this formula, e is 1 if it is a stoichiometric composition, but it may deviate from the stoichiometric composition, and if it is 0.9 or more and 1 or less, sinterability can be improved and higher. It is preferable because piezoelectric characteristics can be obtained. The composition of potassium and bismuth and the composition of oxygen are determined from the stoichiometric composition and may deviate from the stoichiometric composition.

  Barium dititanate has a monoclinic structure (Monoclinic).

BT2 is represented by the general chemical formula Ba _f Ti ₂ O ₅ . In this formula, f is 1 if it is a stoichiometric composition, but it may deviate from the stoichiometric composition, and if it is 0.9 or more and 1.1 or less, the stability of sinterability is obtained. Is preferable. The composition of barium and titanium and the composition of oxygen are determined from the stoichiometric composition, and may deviate from the stoichiometric composition.

In the present embodiment, the heat resistance is enhanced by combining three kinds of materials having a high Curie point of 300 ° C. or higher. For example, compared to the case of a three-component material having a Curie point of 130 ° C. such as BT. also it is characterized by obtaining a piezoelectric ceramic composition having both maintenance and is heat-resistant residual polarization Pr properties at high temperatures and excellent excellent piezoelectric strain constant d _33.

  Furthermore, the inventors measured and compared the residual polarization value (Pr) at each temperature in order to investigate the degree of heat resistance, and when the rate of change of Pr at a temperature of 150 ° C. is large, the heat resistance deteriorates. Thus, it was found that the heat resistance was judged by comparing the rate of change of the remanent polarization value Pr between 150 ° C. and room temperature. This is because the hysteresis of the polarization P-electric field E changes greatly when some phase transition occurs at 150 ° C. or lower, which is considered to affect the piezoelectric characteristics.

  The piezoelectric ceramic composition of the present embodiment exhibits an effect excellent in piezoelectric strain characteristics at high temperature due to a synergistic effect combining three components having a high Curie point. In particular, when the BT2 phase is present in the piezoelectric ceramic composition, further excellent heat resistance can be obtained.

  This piezoelectric ceramic composition is mainly composed of these BNT, BKT, and BT2, and as a subcomponent, a transition metal element (group 3 to group 11 element in the long-period periodic table), alkali metal element, alkaline earth It may contain at least one of a group metal element, a group 12 element in the long-period periodic table, and a group 13 metal element in the long-period periodic table. This is because the mechanical quality factor can be improved. Here, the main component means 90% or more with respect to the total molar ratio of the components constituting the material composition.

  Specifically, for transition metal elements (excluding rare earth elements), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), tungsten ( W) or molybdenum (Mo). For rare earth elements, yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb) Dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and the like.

  Examples of the alkali metal element include lithium (Li), rubidium (Rb), and cesium (Cs). Examples of the alkaline earth metal element include magnesium (Mg), calcium (Ca), and strontium (Sr). If it is a group 12 element, zinc (Zn) etc. will be mentioned. Examples of group 13 metal elements include aluminum (Al), gallium (Ga), and indium (In).

  Among these, Cr, Fe, Co, and Ni are preferable because high effects can be obtained on the piezoelectric characteristics. When the piezoelectric ceramic composition has a polycrystalline structure, these subcomponents exist between the grains composed of the main component, that is, in the vicinity of the grain boundary. Or it diffuses in the particle | grains comprised with a main component, and becomes a part of element which comprises particle | grains. In order to ensure good piezoelectricity, it is preferable that a phase exists in the vicinity of the grain boundary.

  In addition, although this piezoelectric ceramic composition may contain Pb as an impurity, it is preferable that the content is 1 mass% or less, and it is more preferable if it does not contain lead at all. It is possible to minimize lead volatilization during firing and lead release into the environment after being marketed and disposed of as piezoelectric components. It is because it is preferable.

  In addition, the average particle diameter of the crystal particles of the piezoelectric ceramic composition is preferably, for example, 0.5 μm to 20 μm from the viewpoint of exhibiting piezoelectric characteristics and mechanical strength.

  The piezoelectric ceramic composition having such a configuration can be manufactured, for example, as follows.

First, as starting materials for main components, for example, bismuth oxide (Bi ₂ O ₃ ), sodium carbonate (Na ₂ CO ₃ ), potassium carbonate (K ₂ CO ₃ ), barium carbonate (BaCO ₃ ), and titanium oxide (TiO _2). ) Oxide powder can be used.

  In addition, when subcomponents are added, powders such as oxides containing at least one of transition metal elements, alkali metal elements, alkaline earth metal elements, group 12 elements and group 13 metal elements are required as starting materials. Can be used. In addition, the starting material may be an oxide that is obtained by firing, such as carbonate or oxalate, instead of an oxide. A thing may be used. Since it is necessary to strictly adjust the A-site component and the B-site component, for example, when preparing the starting material, it is necessary to devise a method for eliminating the compositional deviation. For example, in order to sufficiently remove the moisture adsorbing the starting material, it is effective to dry it at 100 ° C. or higher.

  Subsequently, for example, the weighed starting materials are thoroughly mixed in an organic solvent or water for 5 hours to 20 hours by a ball mill or the like, then sufficiently dried, press-molded, and then at 750 ° C. to 950 ° C. for 1 hour to 20 hours. Calcinate to a degree. For example, the calcined product is pulverized in an organic solvent or water for 10 to 30 hours by a ball mill or the like, then dried again, and granulated with a binder. After granulation, for example, this granulated powder is press-molded by applying a load of 100 MPa to 400 MPa using a uniaxial press molding machine or a hydrostatic pressure molding machine (CIP) to form pellets.

  After forming into a pellet form, for example, the compact is heat-treated at 400 ° C. to 800 ° C. for about 2 hours to 4 hours to volatilize the binder, and then subjected to main firing at 950 ° C. to 1300 ° C. for about 2 hours to 4 hours. The rate of temperature increase and the rate of temperature decrease during the main firing are, for example, about 50 ° C./hour to 300 ° C./hour. After the main firing, the obtained sintered body is polished as necessary to provide an electrode. For electrode formation, an electrode paste may be applied and baked, or an electrode film may be formed by vapor deposition or sputtering film formation. After that, polarization treatment is performed by applying an electric field of 5 MV / m to 10 MV / m in silicon oil at 25 ° C. to 200 ° C. for about 5 minutes to 1 hour. Thereby, the piezoelectric ceramic composition mentioned above is obtained.

  As another method, at least one component of BNT, BKT, and BT2 may be preliminarily calcined and mixed, and other methods may be prepared in accordance with the above. In particular, it is more preferable to calcine alone to ensure that BT2 is contained.

  As described above, according to the present embodiment, since each phase of BNT, BKT, and BT2 is included, or because a solid solution including these is included, one-component system or two-component system is used. Alternatively, it is possible to achieve both a good piezoelectric strain constant and heat resistance as compared with three components including a component having a low Curie point such as BT.

  Therefore, the possibility of utilization can also be enhanced for piezoelectric ceramic compositions that do not contain lead or have a low lead content. That is, low volatility, environmental friendliness, and ecological aspects that can minimize the volatilization of lead during firing and the release of lead into the environment after being marketed and discarded as piezoelectric components Therefore, it is possible to utilize an extremely excellent piezoelectric ceramic composition.

  FIG. 1 is a three-component composition diagram showing a preferred composition of a piezoelectric ceramic composition according to the present invention. The three components of the piezoelectric ceramic composition of the invention are represented by the three-component composition diagram (a, bKT-cBT2), where the molar ratios of BNT, BKT, and BT2 are a, b, and c (hereinafter, the composition ratio is represented by aBNT-bBKT-cBT2) b, c), A (0.61, 0.38, 0.01), B (0.41, 0.58, 0.01), C (0.51, 0.38, 0.11) ), D (0.31, 0.58, 0.11) (including the line connecting the points). (A + b + c = 1) Here, when there is too much BNT, antiferroelectricity will become strong, and when there is too little, a piezoelectric strain constant will fall easily. And if there is too much BKT, a piezoelectric-strain constant will fall easily, and if too few, heat resistance will fall easily. Furthermore, if the amount of BT2 is too large, the piezoelectric strain constant tends to decrease, and if it is too small, the heat resistance tends to decrease.

  FIG. 2 shows a configuration example of a piezoelectric element using the piezoelectric ceramic composition according to the present embodiment. This piezoelectric element includes a piezoelectric substrate 1 made of the piezoelectric ceramic composition of the present embodiment, and a pair of electrodes 2 and 3 provided on a pair of opposing surfaces 1a and 1b of the piezoelectric substrate 1, respectively. The piezoelectric substrate 1 is polarized, for example, in the thickness direction, that is, in the opposite direction of the electrodes 2 and 3, and when a voltage is applied through the electrodes 2 and 3, the piezoelectric substrate 1 comes to vibrate longitudinally in the thickness direction. Yes.

  The electrodes 2 and 3 are made of metal such as gold (Au), for example, and are provided on the entire opposing surfaces 1 a and 1 b of the piezoelectric substrate 1. An external power source (not shown) is electrically connected to the electrodes 2 and 3 via, for example, a wire (not shown).

  This piezoelectric element can be manufactured by a conventional method. For example, first, a piezoelectric ceramic composition is prepared as described above, and then processed into a predetermined size as necessary to form the piezoelectric substrate 1. Next, the electrodes 2 and 3 are deposited on the piezoelectric substrate 1, for example, to obtain the piezoelectric element shown in FIG.

  FIG. 3 shows another configuration example of the piezoelectric element using the piezoelectric ceramic composition according to the present embodiment. This piezoelectric element includes, for example, a laminate 10 in which a plurality of piezoelectric layers 11 and a plurality of internal electrodes 12 made of the piezoelectric ceramic composition of the present embodiment are alternately laminated. The thickness per layer of the piezoelectric layer 11 is preferably about 1 μm to 100 μm, for example, and the number of stacked layers of the piezoelectric layer 11 is determined according to the target displacement.

The internal electrode 12 contains a conductive material. The conductive material is not particularly limited, but for example, at least one selected from the group consisting of silver (Ag), gold (Au), platinum (Pt), and palladium (Pd), or an alloy thereof is preferable. In addition, the internal electrode 12 may contain about 0.1% by mass or less of various trace components such as phosphorus (P) in addition to these. The thickness of the internal electrode 12 is preferably about 0.5 μm to 3 μm, for example.

  For example, the internal electrodes 12 are alternately extended in opposite directions, and a pair of terminal electrodes 21 and 22 electrically connected to the internal electrode 12 are provided in the extending direction. The terminal electrodes 21 and 22 are formed by baking terminal electrode paste, for example. This terminal electrode paste contains, for example, a conductive material, glass frit, and a vehicle. The conductive material includes, for example, at least one selected from the group consisting of silver, gold, copper, nickel, palladium, and platinum. Examples of the vehicle include an organic vehicle and an aqueous vehicle. The organic vehicle is obtained by dissolving a binder in an organic solvent, and the aqueous vehicle is obtained by dissolving a water-soluble binder and a dispersant in water.

  This piezoelectric element can be manufactured as follows, for example. First, a pre-fired powder is formed in the same manner as in the method for manufacturing a piezoelectric ceramic composition described above, and a vehicle is added thereto and kneaded to prepare a piezoelectric layer paste. Next, the above-described conductive material for forming the internal electrode 12 or various oxides, organometallic compounds, or resinates that become the above-described conductive material after firing are kneaded with a vehicle to prepare an internal electrode paste. Note that additives such as a dispersant, a plasticizer, a dielectric material, and an insulator material may be added to the internal electrode paste as necessary.

  Subsequently, using these piezoelectric layer paste and internal electrode paste, a green chip which is a precursor of the laminate 10 is manufactured by, for example, a printing method or a sheet method. After that, the binder removal treatment is performed and the laminate 10 is formed by firing.

  After forming the laminated body 10, end face polishing is performed by, for example, barrel polishing or sand blasting, and the terminal electrode paste prepared in the same manner as the internal electrode paste is printed or transferred and baked to form the terminal electrodes 21 and 22. . Thereby, the piezoelectric element shown in FIG. 3 is obtained.

  Furthermore, specific examples of the present invention will be described.

(Examples 1 to 11)
BNT is (Na _0.5 Bi _0.5 ) dTiO ₃ (d = 1.0), BKT is (K _0.5 Bi _0.5 ) eTiO ₃ (e = 1.0), BT2 is Ba _f Ti ₂ Bismuth oxide (Bi ₂ O ₃ ), sodium carbonate (Na ₂ CO ₃ ), potassium carbonate (K ₂ CO ₃ ), barium carbonate (BaCO ₃ ) and titanium oxide so as to be O ₅ (f = 1.0) (TiO ₂ ) was sufficiently dried at 100 ° C. or higher and then weighed. The weighed starting materials were mixed with a ball mill for 15 hours, dried, press-molded, and calcined at 850 ° C. for 4 hours to obtain a calcined product. And this calcined material was grind | pulverized for 5 hours with the ball mill, and the BNT, BKT, and BT2 starting material was obtained. Next, when the blending ratio of the starting materials is aBNT + bBKT + cBT2 (a + b + c = 1.0), the composition ratios a, b and c according to the molar ratio after firing are weighed so as to be as shown in Table 1, and are measured by a ball mill. The mixture was pulverized for 10 hours to obtain a mixed powder.

  Further, the obtained mixture was granulated by adding a binder, and a press molding machine was applied with a load of 100 MPa to form a pellet. And as shown in Table 1, it baked at 1000-1200 degreeC, and obtained the sintered body (piezoelectric ceramic composition composition). Then, the fired body obtained was polished into a parallel plate shape having a thickness of 0.5 mm, and an electrode was formed by baking a silver paste on both surfaces at 650 ° C. Further, polarization treatment was performed by applying an electric field of 3 to 10 MV / m in 120 ° C. silicone oil for 15 minutes. Thus, piezoelectric ceramic compositions of test pieces (piezoelectric elements) for evaluating piezoelectric characteristics of Examples 1 to 11 shown in Table 1 were obtained.

For the obtained piezoelectric ceramic compositions of Examples 1 to 11, the piezoelectric strain constant d ₃₃ and the remanent polarization value Pr were measured. At that time, the piezoelectric strain constant d ₃₃ is measured at room temperature by PIEZO d ₃₃ METER MODEL ZJ-4B (manufactured by INSTITUTE OF ACOUSTICS ACADEMIA SINICA), and the residual polarization value Pr is measured by RT6000HVS HIGH VOLTAGE TEST TYPE DIST ) And applying a voltage of 3 to 5 MV / m in silicon oil. The measurement temperature at this time was room temperature and 150 ° C., and the rate of change at 150 ° C. with respect to Pr at room temperature was ΔPr. The equation is shown below as Equation 1.
ΔPr (%) = [(Pr at 150 ° C.) − (Pr at room temperature)] / (Pr at room temperature) × 100 (1)
Further, Table 2 shows the obtained results.

(Comparative Examples 1-10)
Further, in Comparative Examples 1 to 10, the above-described Examples except that the composition ratios a, b, and c, which are molar ratios of the starting materials, were changed as shown in Table 1. A piezoelectric ceramic composition was produced under the same conditions as in No. 1. Furthermore, also in Comparative Examples 1 to 10, the piezoelectric strain constant d ₃₃ and the remanent polarization value Pr were measured. The results are also shown in Table 1.

The evaluation of the piezoelectric characteristics of the piezoelectric ceramic composition is shown in Table 1 as Ox. In this evaluation, a d ₃₃ value of 100 pC / N or more was considered good in order to ensure practical piezoelectric characteristics. Further, as an effect that the piezoelectricity is not extremely lowered even at a high temperature, that is, the polarization deterioration is small even at a high temperature, ΔPr is set to be excellent at −40% or more. The case where both of these were satisfied was determined as “good”, and the case where either or both were not satisfied was determined as “inadequate”.

From these results, a piezoelectric ceramic composition mainly composed of the three components BNT, BKT, and BT2 has a general formula as a region in which piezoelectric characteristics and heat resistance (deterioration of piezoelectric characteristics are small even at high temperatures) are favorable. aBNT-bBKT-cBT2 has a, b, and c in the region surrounded by the composition points A, B, C, D in the ternary composition diagram of BNT-BKT-BT2 in FIG. 1 (on the line connecting the points). Included) (a + b + c = 1.0), but found to be good. Here, BNT is (Bi _0.5 Na _0.5 ) _d TiO ₃ (d = 1.0), BKT is (Bi _0.5 K _0.5 ) _e TiO ₃ (e = 1.0, BT2 represents Ba _f Ti ₂ O ₅ (f = 1.0), and the respective composition points are A (0.61, 0.38, 0.01), B (0.41, 0.58). , 0.01), C (0.51, 0.38, 0.11), and D (0.31, 0.58, 0.11).

(Examples 12 to 17)
In Examples 12 to 17, a, b, and c of aBNT + bBKT + cBT2 were set to a = 0.46, b = 0.48, and c = 0.06. Furthermore, the composition ratio d of (Na _0.5 Bi _0.5 ) _d TiO ₃ that is BNT and (K _0.5 Bi _0.5 ) _e TiO ₃ and Ba _f Ti ₂ O ₅ that is BT 2 is BNT. A piezoelectric ceramic composition was produced under the same conditions as in Example 1 except that e and f were changed as shown in Table 3 except that the mixing ratio of the starting materials and the firing temperature were changed. .
Similarly, in Examples 12 to 17, the piezoelectric strain constant d ₃₃ and the remanent polarization value Pr were measured. The results are also shown in Table 4.

  From these results, it was confirmed that the ranges of 0.9 ≦ d ≦ 1.0, 0.9 ≦ e ≦ 1.0, and 0.9 ≦ f ≦ 1.1 were favorable.

(Comparative Examples 11 and 12)
Furthermore, in place of the piezoelectric ceramic composition BT2 having three components of the general formula aBNT-bBKT-cBT2 as main components, BaTiO ₃ (BT) is used, and the three components of gBNT + hBKT + qBT (g + h + q = 1.0) are used as the main components. Piezoelectric ceramic composition
BNT: (Na _0.5 Bi _0.5 ) TiO ₃ and BKT: (K _0.5 Bi _0.5 ) TiO ₃ were respectively changed in the starting material mixing ratio and firing temperature as shown in Table 5. Except for the above, a piezoelectric ceramic composition was prepared under the same conditions as in Example 1 described above. The piezoelectric strain constant d ₃₃ and the remanent polarization value Pr were measured and evaluated.

  The piezoelectric ceramic composition and the piezoelectric element according to the present invention can be applied in the fields of actuators, sensors, resonators, and the like.

DESCRIPTION OF SYMBOLS 1 Piezoelectric substrate 2, 3 Electrode 1a, 1b Opposite surface 10 Laminated body 11 Piezoelectric layer 12 Internal electrode 21, 22 Terminal electrode

Claims (3)

  When the three components of bismuth sodium titanate, potassium bismuth titanate, and barium dititanate are at least the main components and the molar ratio of bismuth sodium titanate, bismuth potassium titanate, and barium dititanate is a: b: c ( Sodium bismuth titanate: potassium bismuth titanate: barium dititanate = a: b: c), where the composition range of (a, b, c) is A (0.61, 0.00). 38, 0.01), B (0.41, 0.58, 0.01), C (0.51, 0.38, 0.11), D (0.31, 0.58, 0.11) ) In a region surrounded by (including a line connecting each point). The general chemical formulas of the three components are as follows: sodium bismuth titanate (Bi _0.5 Na _0.5 ) _d TiO ₃ , potassium bismuth titanate (Bi _0.5 K _0.5 ) _e TiO ₃ , barium dititanate Is Ba _f Ti ₂ O ₅ , d is 0.9 ≦ d ≦ 1.0, e is 0.9 ≦ e ≦ 1.0, and f is 0.9 ≦ f ≦ 1.1. 2. The piezoelectric ceramic composition according to claim 1, wherein A piezoelectric element comprising the piezoelectric ceramic composition according to claim 1.

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