JP2011251866A - Piezoelectricity/electrostriction ceramic sintered compact, and piezoelectricity/electrostrictive element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectricity/electrostriction ceramic sintered compact excellent in strain characteristics at the time of high electric field impression.SOLUTION: The piezoelectricity/electrostriction ceramic sintered compact comprises a non-lead piezoelectricity/electrostrictive material, wherein a defect has generated in which a ratio of at least one metal component of metal components which compose the non-lead piezoelectricity/electrostrictive material has shifted from a stoichiometric composition by at least 1% in a mole conversion, and a degree of orientation of a c-axis measured by a Lotgering method is at least 30%. Moreover, since the sintered compact comprises the non-lead piezoelectricity/electrostrictive material which does not contain lead, there is no elution of lead from the sintered compact, and a problem of environmental pollution is not generated.

Description

  The present invention relates to a piezoelectric / electrostrictive ceramic sintered body and a piezoelectric / electrostrictive element. More specifically, the present invention relates to a piezoelectric / electrostrictive ceramic sintered body and a piezoelectric / electrostrictive element that have excellent strain characteristics when a high electric field is applied.

  Piezoelectric actuators have the advantage that displacement can be precisely controlled on the order of submicrons. In particular, a piezoelectric actuator using a piezoelectric / electrostrictive ceramic sintered body as a piezoelectric / electrostrictive body (piezoelectric / electrostrictive element) has high electromechanical conversion efficiency in addition to precisely controlling the above displacement. Since it has the advantages of high power, high response speed, high durability, and low power consumption, it has been used in inkjet printer heads, diesel engine injectors, etc., taking advantage of these advantages.

As a piezoelectric / electrostrictive ceramic sintered body for such a piezoelectric actuator, a lead zirconate titanate {Pb (Zr, Ti) O ₃ , PZT} -based material has been conventionally used. The use of non-lead piezoelectric / electrostrictive materials based on alkali niobate has been studied since the impact of lead elution from the sintered ceramics on the global environment is strongly concerned (for example, , Patent Document 1, Non-Patent Documents 1 to 4).

  For the same reason, the use of lead-free piezoelectric / electrostrictive materials such as bismuth sodium titanate (hereinafter sometimes referred to as “BNT”) is also being studied (for example, see Non-Patent Document 5). . In such BNT-based lead-free piezoelectric / electrostrictive materials, bismuth potassium titanate (hereinafter sometimes referred to as “BKT”) and barium titanate (hereinafter sometimes referred to as “BT”) are fixed to the BNT. Attempts have been made to increase the electric field induced strain important for piezoelectric / electrostrictive actuators by melting.

  Further, in such a lead-free piezoelectric / electrostrictive material, there has been proposed a crystal-oriented ceramic in which the degree of orientation is increased to obtain more uniform crystal particles (see, for example, Patent Documents 2 and 3). However, in Patent Documents 2 and 3, after a molded body having a crystal grain structure with a high degree of orientation is produced and fired, the obtained fired body is further pulverized to obtain plate-like polycrystalline particles. The present invention relates to a technique of using polycrystalline particles as a raw material for, for example, a piezoelectric / electrostrictive ceramic sintered body.

  In addition, for non-lead piezoelectric / electrostrictive materials such as alkali niobate-based materials described above, for example, a technique for improving the strain characteristics during electric field application by causing defects in the solid solution by composition control or atmosphere control is also disclosed. (For example, see Patent Documents 4 and 5).

JP 2006-280001 A JP 2009-46376 A JP 2009-10672 A International Publication No. 2006/095716 Pamphlet US Patent Application No. 2010/0123370

M.M. Matsubara et. al. , Jpn. J. et al. Appl. Phys. 44 (2005) pp. 6136-6142. E. Hollenstein et. al. , Appl. Phys. Lett. 87 (2005) 182905. Y. Guo et. al. , App. Phys. Lett. 85 (2004) 4121 Y. Saito et. al. , Nature 432, 84-87 (2004). Teranishi et al., “Giant strain characteristics in (Bi0.5Na0.5) TiO3 series ferroelectrics”, Abstracts of the 46th Ceramics Science Forum, Japan Ceramic Society, Basic Sciences, January 2008, p. 482-483

  However, even in the piezoelectric / electrostrictive ceramic sintered body using such a conventional lead-free piezoelectric / electrostrictive material, 31 direction (direction perpendicular to the electric field application direction) and 33 when an electric field is applied. The strain characteristics in the direction (parallel to the direction of electric field application) are not yet sufficient, and there is a demand for the development of a piezoelectric / electrostrictive ceramic sintered body having excellent strain characteristics.

  The present invention has been made in view of such problems of the prior art, and provides a piezoelectric / electrostrictive ceramic sintered body and a piezoelectric / electrostrictive element having excellent strain characteristics when a high electric field is applied. It is.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor is likely to deviate by 1% or more in terms of mole from the stoichiometric composition of at least one of the metal components constituting the piezoelectric / electrostrictive material. The present inventors have found that the strain characteristics can be improved by causing various defects and setting the degree of orientation of the C-axis to 30% or more, thereby completing the present invention. According to the present invention, the following piezoelectric / electrostrictive ceramic sintered body and piezoelectric / electrostrictive element are provided.

[1] It is composed of a lead-free piezoelectric / electrostrictive material, and the ratio of at least one metal component of the metal components constituting the lead-free piezoelectric / electrostrictive material is 1% in terms of mole from the stoichiometric composition. Piezoelectric / electrostrictive ceramics sintered body that has the above-mentioned defect and has an orientation degree of C axis of 30% or more measured by the Lotgering method.

[2] The piezoelectric / electrostrictive ceramic sintered body according to [1], wherein the lead-free piezoelectric / electrostrictive material has a perovskite structure represented by the following general formula (1).
ABO ₃ (1)
(However, A represents an A site constituent element and B represents a B site constituent element)

[3] The A site constituent element includes at least one selected from the group consisting of Li, Na, K, Bi, and Ba, and the B site constituent element includes Nb, Ta, Sb, Ti, and The piezoelectric / electrostrictive ceramic sintered body according to [2], including at least one selected from the group consisting of Fe.

[4] The piezoelectric / electrostrictive ceramic sintered body according to any one of [1] to [3], wherein the degree of orientation of the C axis measured by the Lotgering method is 70 to 92%.

[5] A film-like piezoelectric / electrostrictive body made of the piezoelectric / electrostrictive ceramic sintered body according to any one of [1] to [4], and the piezoelectric / electrostrictive body are interposed. A piezoelectric / electrostrictive element comprising: a pair of electrodes; and a substrate bonded to any surface of the pair of electrodes.

  The piezoelectric / electrostrictive ceramic sintered body and the piezoelectric / electrostrictive element of the present invention have defects in which the ratio of at least one metal component of the constituent metal components deviates by 1% or more in terms of mole from the stoichiometric composition. In addition, the degree of orientation of the C-axis measured by the Lotgering method is 30% or more, and in either the direction perpendicular to the electric field application direction (31 directions) or the parallel direction (33 directions) In contrast, strain characteristics (electric field induced strain) can be improved. In particular, the electric field induced strain in the 33 direction can be greatly improved as compared with the conventional one.

  Furthermore, the piezoelectric / electrostrictive ceramic sintered body and the piezoelectric / electrostrictive element of the present invention are excellent in other electrical characteristics such as piezoelectric constant and dielectric characteristics, in addition to the above-described strain characteristics and temperature dependence. Yes.

It is sectional drawing which shows typically one Embodiment of the piezoelectric / electrostrictive element of this invention. It is sectional drawing which shows typically other embodiment of the piezoelectric / electrostrictive element of this invention. It is sectional drawing which shows typically other embodiment of the piezoelectric / electrostrictive element of this invention. It is a perspective view which shows typically other embodiment of the piezoelectric / electrostrictive element of this invention. It is a longitudinal cross-sectional view of the piezoelectric / electrostrictive element shown in FIG. It is a cross-sectional view of the piezoelectric / electrostrictive element shown in FIG. FIG. 5 is an exploded perspective view of a part of the piezoelectric / electrostrictive element shown in FIG. 4.

  Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments, and based on ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. It should be understood that modifications, improvements, and the like appropriately added to the embodiments described above fall within the scope of the present invention.

(1) Piezoelectric / electrostrictive ceramic sintered body:
First, an embodiment of the piezoelectric / electrostrictive ceramic sintered body of the present invention will be specifically described. The piezoelectric / electrostrictive ceramic of the present embodiment is made of a lead-free piezoelectric / electrostrictive material, and the ratio of at least one metal component of the metal components constituting the lead-free piezoelectric / electrostrictive material is a stoichiometric amount. A defect deviated by 1% or more in terms of mole from the theoretical composition is produced, and the degree of orientation of the C axis measured by the Lotgering method is 30% or more.

  The piezoelectric / electrostrictive ceramics sintered body of this embodiment configured as described above is excellent in strain characteristics when a high electric field is applied (hereinafter sometimes referred to as “electric field induced strain” as appropriate). That is, it has excellent distortion characteristics in 31 directions (a direction perpendicular to the electric field application direction) and 33 directions (a direction parallel to the electric field application direction) when a high electric field is applied. This is a significant improvement over the conventional one.

  Furthermore, the piezoelectric / electrostrictive ceramic sintered body of the present embodiment is excellent in other electrical characteristics such as a piezoelectric constant and a dielectric characteristic in addition to the above-described strain characteristics. Further, since it is composed of a lead-free piezoelectric / electrostrictive material that does not contain lead, there is no elution of lead from the sintered body, and there is no problem of environmental pollution.

(1-1) Configuration of piezoelectric / electrostrictive ceramic sintered body:
The piezoelectric / electrostrictive ceramic sintered body of this embodiment is a ceramic sintered body made of a lead-free piezoelectric / electrostrictive material. The lead-free piezoelectric / electrostrictive material refers to a piezoelectric / electrostrictive material that does not contain lead in its constituent metal components.

  In the piezoelectric / electrostrictive ceramics sintered body of this embodiment, the ratio of at least one metal component of the metal components constituting the lead-free piezoelectric / electrostrictive material is 1 in terms of mole from the stoichiometric composition. %, A defect shifted by more than%.

  The above-mentioned “defect” means that the chemical composition is expressed by a non-stoichiometric composition ratio due to the ratio of the constituent metal components deviating from the stoichiometric composition. And “expressed by a non-stoichiometric composition ratio” means that the ratio of each element constituting the piezoelectric / electrostrictive ceramic sintered body is not expressed by a simple integer ratio. For example, the ratio (molar ratio) of the transition metal element group including Nb and Ta constituting the B site to the alkali metal element (group) 1 constituting the A site of the perovskite structure is not represented by an integer. .

  As described above, by producing defects in which the ratio of the metal component deviates from the stoichiometric composition by 1% or more in terms of mole, it is dense and crystallized even when fired at low temperature conditions as compared with the conventional case. It is possible to obtain a piezoelectric / electrostrictive element that has excellent electrical properties and exhibits electrical characteristics such as excellent electric field induced strain.

  The reason why the above-described effect can be obtained is considered to be that, for example, when the metal element at the A site constituting the perovskite structure becomes excessive, the surface energy due to defects increases and the driving force increases. Moreover, since it becomes easy to grow a grain in connection with this, it becomes possible to reduce a calcination temperature. In addition, in the conventional piezoelectric / electrostrictive ceramic sintered body represented by the stoichiometric composition ratio, it is presumed that densification of the fired surface is difficult to promote because the self-shaped shape is likely to occur on the fired surface. On the other hand, it is considered that by forming defects, it becomes difficult for self-formation to occur on the fired surface due to the inclusion of strain in the lattice, and densification of the fired surface is promoted.

In the piezoelectric / electrostrictive ceramic sintered body of the present embodiment, the above-mentioned lead-free piezoelectric / electrostrictive material preferably has a perovskite structure represented by the following general formula (1).
ABO ₃ (1)
(However, A represents an A site constituent element and B represents a B site constituent element)

  By using a material having such a perovskite structure, it is easy to cause a defect in at least one of the constituent metal components (that is, the metal component contained in the A site and the B site). Is relatively easy to control (ie, the ratio of deviation from the stoichiometric composition).

  Examples of the A site constituent element include those containing at least one selected from the group consisting of Li, Na, K, Bi, and Ba, and examples of the B site constituent element include Nb, for example. And at least one selected from the group consisting of Ta, Sb, Ti, and Fe.

  These materials may further contain at least one additive element selected from the group consisting of strontium, calcium, and manganese.

  Examples of such materials include niobic acid-based lead-free piezoelectric / electrostrictive materials such as potassium sodium niobate, and bismuth sodium titanate (BNT) -based lead-free piezoelectric / electrostrictive materials. The BNT-based lead-free piezoelectric / electrostrictive material may be a material in which bismuth potassium titanate (BKT) or barium titanate (BT) is dissolved in BNT. Hereinafter, the BNT material and the material (solid solution) in which BKT or BT is dissolved in the BNT material may be referred to as “BNT-BKT-BT material”. The lead-free piezoelectric / electrostrictive material is strontium bismuth tantalate, copper tungsten barium, bismuth ferrate, or a composite oxide composed of two or more lead-free piezoelectric / electrostrictive materials described so far. Also good.

  The selection of these materials is not particularly limited as long as the necessary performance as a device is satisfied.

  The defect due to deviation from the stoichiometric composition may be 1% or more in terms of mole, but is preferably 1 to 10%, more preferably 1 to 7%, and more preferably 1 to 5%. It is particularly preferred. By configuring in this way, electrical characteristics such as electric field induced strain can be improved satisfactorily. For example, if it is less than 1%, the effect of improving the electric field induced strain cannot be sufficiently obtained, and if it exceeds 10%, a short circuit may occur when a high voltage is applied.

  The degree of orientation of the C axis is more preferably 70 to 92%. By comprising in this way, the crack which arises at the time of a high voltage application can be suppressed. can do. In the present invention, the “degree of orientation of the C axis” means the degree of orientation of the crystal plane (100).

  In addition, there is no restriction | limiting in particular about the method of producing a defect about a metal component, The various method which can produce a defect about a metal component can be used. For example, it can be performed by adjusting the amount of raw material used at the stage of raw material blending so that the final fired product (piezoelectric / electrostrictive ceramic sintered body) has a non-stoichiometric composition. In addition, after firing the raw material of the piezoelectric / electrostrictive ceramics, it can be realized by performing an annealing process for performing a high temperature heat treatment in an atmosphere in which the oxygen partial pressure is controlled. Moreover, you may combine these methods.

Here, the “orientation degree by the Lotgering method” is obtained by measuring the XRD diffraction pattern of the target piezoelectric / electrostrictive ceramic sintered body and by the following equation (2). In the following formula (2), ΣI (HKL) is the sum of X-ray diffraction intensities of all crystal planes (hkl) measured by the piezoelectric / electrostrictive ceramic sintered body, and ΣI ₀ (hkl) is piezoelectric / electron. This is the sum of the X-ray diffraction intensities of all crystal planes (hkl) measured for a non-oriented material having the same composition as the strained ceramic sintered body, and Σ'I (HKL) is the piezoelectric / electrostrictive ceramic sintered body Is the sum of the X-ray diffraction intensities of the crystallographically equivalent specific crystal plane ((100) plane) measured in (1), and Σ′I ₀ (HKL) has the same composition as the piezoelectric / electrostrictive ceramic sintered body It is the sum total of the X-ray diffraction intensities of a specific crystal plane measured for a non-oriented material.

  Regarding the measurement of the XRD diffraction pattern in the calculation of the degree of orientation, for example, when waviness is generated in the sheet-like piezoelectric / electrostrictive ceramic sintered body, measurement is performed in a state where the surface is exposed using the smallest waviness portion. Shall. In addition, when it is difficult to surface, such as a piezoelectric / electrostrictive ceramic sintered body in a roll shape, the crushed material obtained by crushing the piezoelectric / electrostrictive ceramic sintered body is placed on a substrate such as glass. The measurement is performed after coating so that the crystal plane is parallel to the substrate surface. As a specific method, for example, the piezoelectric / electrostrictive ceramic sintered body is crushed to obtain a crushed material, and the obtained crushed material is put in an amount corresponding to 1 to 10% by mass in a solvent such as alcohol, For example, it is dispersed over 30 minutes using ultrasonic waves or the like. Thereafter, the dispersion is spin-coated under a condition of 1000 to 4000 rpm, and coated on a substrate such as glass. In coating, the crushed material is dispersed in a thin layer so that the crushed material is not overlapped as much as possible and the crystal plane included in the crushed material is parallel to the substrate surface. The XRD diffraction pattern of the crushed material on the substrate thus obtained is measured to obtain an XRD diffraction pattern of the piezoelectric / electrostrictive ceramic sintered body.

  In the piezoelectric / electrostrictive ceramics sintered body of the present embodiment, the method for controlling the degree of orientation is not particularly limited. For example, reactive template grain growth (RTGG), template grain growth ( Methods such as TGG (Templated grain growth), hot forge, and magnetic field orientation can be used.

  For example, in the reactive template grain growth method, a slurry containing raw material particles for forming a piezoelectric / electrostrictive ceramic sintered body as template particles is prepared, and stress is applied to the obtained slurry by a doctor blade method or the like. By controlling the orientation of the raw material particles in the molded body by molding, the obtained molded body is fired to obtain a sintered body. In addition, you may use what crushed the sintered compact once shape | molded and baked as a raw material particle of a molded object. The orientation of the piezoelectric / electrostrictive ceramic sintered body can be controlled by such a known orientation control method described above.

  Here, an example of the manufacturing method of the piezoelectric / electrostrictive ceramics sintered body of the present embodiment will be described. First, a binder, a plasticizer, a dispersant, and a dispersion medium are added to a raw material powder of a piezoelectric / electrostrictive ceramic sintered body, and these are mixed by a ball mill or the like to prepare a molding slurry. Note that the raw material powder of the piezoelectric / electrostrictive ceramics sintered body may be prepared by adjusting the amount of each raw material so that the final fired product has a non-stoichiometric composition. Moreover, when controlling a defect by oxygen partial pressure etc., you may prepare a slurry using the raw material powder used for manufacture of a conventionally well-known piezoelectric / electrostrictive ceramic sintered compact. Moreover, you may use the powder which calcined and grind | pulverized at 600-1400 degreeC. The calcination and pulverization may be performed a plurality of times.

  Next, the obtained slurry is formed into a sheet or the like by a doctor blade method or the like to obtain a formed body (for example, a green sheet). In addition, there is no restriction | limiting in particular about a shaping | molding method, A conventionally well-known method can be used. At the time of molding, the orientation of the raw material particles in the molded body may be controlled by the above-described methods such as RTGG, TGG, and hot forge. Hot forge is an orientation control method in which shearing stress is applied to the obtained molded body to orient the raw material particles in the molded body in a uniaxial direction. In addition, after obtaining the compact, the raw material particles may be oriented in the direction of the easy axis of magnetization using magnetic anisotropy due to the crystal structure (magnetic field orientation).

  Next, the obtained molded body is fired at 900 to 1500 ° C. to obtain a piezoelectric / electrostrictive ceramic sintered body. Note that, as described above, the defect may be caused by a deviation of 1% or more from the stoichiometric composition by controlling the defect by oxygen partial pressure or the like. Further, if necessary, it may be processed into an appropriate shape (for example, strip shape) and further subjected to polarization treatment.

  In the piezoelectric / electrostrictive ceramics sintered body of the present embodiment, the amount of oxygen defects may be an amount that does not maintain the electrical neutrality of the piezoelectric / electrostrictive ceramics sintered body. Of course, a defect may be generated in oxygen so as to maintain the electrical neutrality of the entire crystal against the defect of the metal component in the piezoelectric / electrostrictive ceramic sintered body.

(2) Piezoelectric / electrostrictive element:
Next, an embodiment of the piezoelectric / electrostrictive element of the present invention will be specifically described. FIG. 1 is a sectional view schematically showing one embodiment of the piezoelectric / electrostrictive element of the present invention. As shown in FIG. 1, the piezoelectric / electrostrictive element 10 of this embodiment includes a film-like piezoelectric / electrostrictive body 2 made of the above-described piezoelectric / electrostrictive ceramic sintered body of the present invention, and the piezoelectric / electrostrictive element. A pair of electrodes 4 and 5 disposed with the body 2 interposed therebetween, and a substrate 1 bonded to one surface of the pair of electrodes are provided.

  The thus configured piezoelectric / electrostrictive element of the present embodiment is superior in electric field induced strain as compared with a conventional piezoelectric / electrostrictive element.

  In FIG. 1, a piezoelectric / electrostrictive element 10 having a single piezoelectric / electrostrictive body 2 is shown. However, the piezoelectric / electrostrictive body is not limited to a single layer, and may be multi-layered. preferable. For example, as shown in FIG. 2, a plurality of piezoelectric / electrostrictive bodies 22, 23 and a plurality of electrodes 24, 25, 26 are provided, and a plurality of piezoelectric / electrostrictive bodies 22, 23 are provided with a plurality of electrodes 24, 25, Alternatively, the piezoelectric / electrostrictive element 30 may be configured to be alternately sandwiched and stacked by 26 (two pairs of electrodes sharing the electrode 25 in FIG. 2). This configuration is a so-called multilayer configuration and is preferable because a large bending displacement can be obtained at a low voltage. Here, FIG. 2 is a cross-sectional view schematically showing another embodiment of the piezoelectric / electrostrictive element of the present invention. Note that. Reference numeral 21 denotes a substrate bonded to one electrode (electrode 24 in FIG. 2).

  As shown in FIG. 1, the piezoelectric / electrostrictive body 2 is fixed on the substrate 1 with the electrode 4 interposed. The piezoelectric / electrostrictive body 2 and the substrate 1 are preferably fixed by close integration by a solid phase reaction between the piezoelectric / electrostrictive body 2 and the substrate 1 without using an adhesive or the like.

  The thickness of the piezoelectric / electrostrictive body 2 constituting the piezoelectric / electrostrictive element 10 is preferably 0.5 to 50 μm, more preferably 0.8 to 40 μm, and 1.0 to 30 μm. It is particularly preferred. If the thickness of the piezoelectric / electrostrictive body 2 is less than 0.5 μm, the densification of the piezoelectric / electrostrictive body 2 may be insufficient. On the other hand, if the thickness of the piezoelectric / electrostrictive body 2 exceeds 50 μm, the contraction stress of the piezoelectric / electrostrictive body 2 during firing increases, and the substrate 1 is thickened to prevent the substrate 1 from being destroyed. Therefore, it may be difficult to reduce the size of the piezoelectric / electrostrictive element.

  The thickness of the substrate 1 is preferably 1 μm to 1 mm, more preferably 1.5 to 500 μm, and particularly preferably 2 to 200 μm. If the thickness of the substrate 1 is less than 1 μm, the mechanical strength of the piezoelectric / electrostrictive element 10 may decrease. On the other hand, when the thickness of the substrate 1 exceeds 1 mm, the rigidity of the substrate 1 with respect to the contraction stress generated when an electric field is applied to the piezoelectric / electrostrictive body 2 increases, and the bending displacement of the piezoelectric / electrostrictive body 2 is increased. May become smaller. Although there is no restriction | limiting in particular about the material of the board | substrate 1, For example, a zirconia etc. can be mentioned.

  Further, as shown in FIG. 3, the piezoelectric / electrostrictive element of the present invention may be one in which a unit structure (laminated body 32) having a multilayer structure as shown in FIG. 2 is repeated. That is, the piezoelectric / electrostrictive element 30 shown in FIG. 3 shows an example in which three laminated bodies 32 having a multilayer structure are fixed on a base 31. Here, FIG. 3 is a sectional view schematically showing still another embodiment of the piezoelectric / electrostrictive element of the present invention.

  In addition, the number of the laminated bodies 32 provided on the base body 31 is not limited to three. Further, it is manufactured in the same manner as the single-layer piezoelectric / electrostrictive element 10 except that the number of laminated bodies to be formed and the number of piezoelectric / electrostrictive films and electrode films are increased.

  Next, a piezoelectric / electrostrictive element as shown in FIGS. 4 to 6 will be described as still another embodiment of the piezoelectric / electrostrictive element of the present invention. As shown in FIGS. 4 to 6, the piezoelectric / electrostrictive element 40 according to the present embodiment includes piezoelectric / electrostrictive films 402 and internal electrode films 404 that are alternately stacked in the direction of the axis A. In this structure, external electrode films 416 and 418 are disposed on end faces 412 and 414 of a laminate 410 in which a body film 402 and an internal electrode film 404 are laminated.

  4 is a perspective view schematically showing still another embodiment of the piezoelectric / electrostrictive element of the present invention. FIG. 5 is a longitudinal sectional view of the piezoelectric / electrostrictive element shown in FIG. 6 is a cross-sectional view of the piezoelectric / electrostrictive element shown in FIG.

  As shown in the exploded perspective view of FIG. 7 showing a state in which a part of the piezoelectric / electrostrictive element 40 is exploded in the direction of the axis A, the internal electrode film 404 reaches the end surface 412 but reaches the end surface 414. There is a first internal electrode film 406 that does not reach, and a second internal electrode film 408 that reaches the end face 414 but does not reach the end face 412. The first internal electrode film 406 and the second internal electrode film 408 are provided alternately.

  The first internal electrode film 406 is in contact with the external electrode film 416 at the end surface 412 and is electrically connected to the external electrode film 416. The second internal electrode film 408 is in contact with the external electrode film 418 at the end face 414 and is electrically connected to the external electrode film 418. Therefore, when the external electrode film 416 is connected to the positive side of the drive signal source and the external electrode film 418 is connected to the negative side of the drive signal source, the first internal electrode film facing the piezoelectric / electrostrictive film 402 is sandwiched. A drive signal is applied to 406 and the second internal electrode film 408, and an electric field is applied in the thickness direction of the piezoelectric / electrostrictive film 402. As a result, the piezoelectric / electrostrictive film 402 expands and contracts in the thickness direction, and the laminated body 410 as a whole is deformed into a shape indicated by a broken line in FIG.

  Unlike the piezoelectric / electrostrictive elements 10, 20, and 30 that have already been described, the piezoelectric / electrostrictive element 40 does not have a base to which the multilayer body 410 is fixed. The piezoelectric / electrostrictive element 40 is also referred to as an “offset type piezoelectric / electrostrictive element” because the first internal electrode film 406 and the second internal electrode film 408 having different patterns are alternately provided.

  The piezoelectric / electrostrictive film 402 is formed by the piezoelectric / electrostrictive ceramic sintered body of the present invention. The film thickness of the piezoelectric / electrostrictive film 402 is preferably 5 to 500 μm. If the thickness is below this range, it is difficult to manufacture the piezoelectric / electrostrictive film 402. Further, if it exceeds this range, it is difficult to apply a sufficient electric field to the piezoelectric / electrostrictive film 402.

  The material of the internal electrode film 404 and the external electrode films 416 and 418 is a metal such as platinum, palladium, rhodium, gold or silver, or an alloy thereof. Among these, the material of the internal electrode film 404 is preferably platinum or an alloy containing platinum as a main component from the viewpoint of high heat resistance during firing and easy co-sintering with the piezoelectric / electrostrictive film 402. . However, an alloy such as silver-palladium is also preferably used depending on the firing temperature.

  The thickness of the internal electrode film 404 is preferably 10 μm or less. This is because exceeding this range, the internal electrode film 404 functions as a relaxation layer and the displacement tends to be small. Further, in order for the internal electrode film 404 to appropriately fulfill its role, the film thickness is preferably 0.1 μm or more.

  4 to 6 illustrate the case where the piezoelectric / electrostrictive film 402 has 10 layers, the piezoelectric / electrostrictive film 402 may have 9 layers or less or 11 layers or more. .

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.

Example 1
In Example 1, an alkali niobate-based piezoelectric / electrostrictive ceramic sintered body was produced, and a piezoelectric / electrostrictive element was produced using this piezoelectric / electrostrictive ceramic sintered body.

  In this example, first, calcined powder and plate-like particles (that is, seed crystal particles), which are raw material powders of a piezoelectric / electrostrictive ceramic sintered body, are prepared, and the calcined powder and plate-like particles are produced. A molded body formed by molding a slurry containing the above by a doctor blade method was fired to produce a piezoelectric / electrostrictive ceramic sintered body.

[Preparation of calcined powder]
In preparing the calcined powder that is the raw material particles of the piezoelectric / electrostrictive ceramic sintered body, lithium carbonate (Li ₂ CO ₃ ), sodium hydrogen tartrate monohydrate (C ₄ H ₅ O ₆ Na · H ₂ O), Powders of raw materials of potassium hydrogen tartrate (C ₄ H ₅ O ₆ K), niobium oxide (Nb ₂ O ₅ ), tantalum oxide (Ta ₂ O ₅ ) and antimony oxide (Sb ₂ O ₃ ) are oxidized after firing. The product was weighed so as to have the composition shown in Table 1. In Table 1, in the columns of “x”, “y”, “z”, “w”, and “a”, the composition of the perovskite oxide is represented by the general formula {Li _y (Na _1−x K _x ) ₁₋ shows _{y} a (Nb 1-z} -w Ta z Sb w) x when expressed in _{O 3,} y, z, the values of w and a.

  Next, alcohol was added as a dispersion medium to the weighed raw material powders and mixed for 16 hours with a ball mill to prepare a mixed raw material.

Next, the obtained mixed raw material was dried with an evaporator and a dryer, and further calcined at 800 ° C. for 5 hours to obtain a calcined body. Next, ethanol is added as a dispersion medium to the obtained calcined body, and pulverization with a ball mill is repeated twice or more, and further dried by an evaporator and a drier to obtain a calcined powder of perovskite oxide (hereinafter referred to as “perovskite oxide”). And “calculated powder A”). Strontium carbonate (SrCO ₃ ) and manganese dioxide (MnO ₂ ) were added after the first calcination. In addition, the said additive can be added after the 1st calcination and / or the 2nd calcination.

[Preparation of plate-like particles]
Next, a mixture of equal amounts of toluene and isopropanol as a dispersion medium, a part of the calcined powder A obtained by the above process, and polyvinyl butyral (trade name “BM-2” manufactured by Sekisui Chemical Co., Ltd.) as a binder. )), A plasticizer (dioctyl phthalate (DOP) manufactured by Kurokin Kasei Co., Ltd.), and a dispersant (trade name “SP-O30” manufactured by Kao Co., Ltd.) (Also called slurry). The amount of each raw material used was 100 parts by mass of the dispersion medium, 10 parts by mass of the binder, 4 parts by mass of the plasticizer, and 2 parts by mass of the dispersant with respect to 100 parts by mass of the powder A.

  Next, the obtained slurry was stirred and defoamed under reduced pressure to prepare a viscosity of 0.5 to 0.7 Pa · s. The viscosity of the slurry was measured with an LVT viscometer manufactured by Brookfield. The obtained slurry was formed into a sheet on a PET film by a doctor blade method. The thickness after drying was 5 μm.

  Next, the sheet-like molded body peeled off from the PET film was cut into a 50 mm square with a cutter and placed on the center of a setter (dimension 70 mm square, height 5 mm) made of zirconia. In this setter, an unsintered sheet molded body (dimensions 5 mm × 40 mm, thickness 100 μm) made of the same molding raw material as the sheet-shaped molded body is placed outside the four sides of the sheet-shaped molded body, and enclosed. A zirconia square plate (size 70 mm square, height 5 mm) was further placed thereon. Thus, the space for the sheet-like molded body was made as small as possible, and the firing conditions were set such that the same molding raw material coexisted. And after baking at 600 degreeC for 2 hours, baking was performed at 1100 degreeC for 5 hours. After firing, the part not welded to the setter was taken out.

  Next, the obtained molded product after firing was placed on a 300 mesh (opening diameter 45 μm) sieve, and this molded product was crushed while being lightly pressed with a spatula, and classified by the above sieve to obtain plate-like particles (hereinafter, "Plate-like particle B") was prepared.

[Preparation of sintered piezoelectric / electrostrictive ceramics]
To a mixture of equal amounts of toluene and isopropanol as a dispersion medium, the calcined powder A, the plate-like particles B, polyvinyl butyral (product surface “BM-2” manufactured by Sekisui Chemical Co., Ltd.) as a binder, plastic An agent (dioctyl phthalate (DOP) manufactured by Kurokin Kasei Co., Ltd.) and a dispersant (trade name “SP-O30” manufactured by Kao Corporation) were mixed to prepare a slurry-like molding raw material. The amount of each raw material used was 30 parts by mass of the plate-like particles B, 100 parts by mass of the dispersion medium, 10 parts by mass of the binder, 4 parts by mass of the plasticizer, and 2 parts by mass of the dispersant with respect to 100 parts by mass of the calcined powder A.

  Next, the obtained forming raw material was stirred and degassed under reduced pressure to prepare a viscosity of 2.5 to 3.0 Pa · s. The viscosity of the molding material was measured with an LVT viscometer manufactured by Brookfield. The obtained forming raw material was formed into a flat plate shape by the doctor blade method so that the plate-like particles B were oriented in one direction and the thickness after drying was 100 μm.

A plurality of the molded bodies thus obtained were laminated and press-molded into a disk shape having a diameter of 18 mm and a plate thickness of 5 mm at a pressure of 2 × 10 ⁸ Pa. Then, the molded body is housed in an alumina container, (1) a first stage in which the temperature is increased from 860 to 900 ° C. at a temperature increase rate of 200 ° C./hour and held for 0.5 to 3 hours, (2) 1000 A second stage in which the temperature is increased from 1000 to 1050 ° C. at a temperature increase rate of 1 ° C./hour and held for 1 minute; (3) the temperature is decreased from 940 to 980 ° C. at a temperature decrease rate of 400 to 2000 ° C./hour, A piezoelectric / electrostrictive ceramic sintered body is obtained by firing using a firing profile that sequentially executes a third stage for holding time and (4) a fourth stage for cooling to room temperature at a temperature decrease rate of 200 ° C./hour. It was. The XRD diffraction pattern of the obtained piezoelectric / electrostrictive ceramic sintered body was measured, and the degree of orientation of the C / axis of the piezoelectric / electrostrictive ceramic sintered body by the Lotgering method (ie, (100 ) Surface orientation degree). Table 1 shows the degree of orientation of the piezoelectric / electrostrictive ceramic sintered body of Example 1. The degree of orientation of the piezoelectric / electrostrictive ceramic sintered body of Example 1 was 85%.

[Preparation of piezoelectric / electrostrictive element]
Next, the obtained piezoelectric / electrostrictive ceramic sintered body was processed into a rectangular shape having a long side of 12 mm, a short side of 3 mm, and a thickness of 1 mm, and heat-treated at 600 to 900 ° C. Thereafter, gold electrodes were formed by sputtering on both main surfaces of the rectangular sample. And this is immersed in 70-100 degreeC silicon oil, the voltage of 5 kV / mm is applied to the gold electrode of both main surfaces for 15 minutes, a polarization process is performed in the thickness direction, and an aging process below 300 degreeC Thus, a piezoelectric / electrostrictive element was produced. The electric field induced strain of the obtained piezoelectric / electrostrictive element was measured by the following method. The results are shown in Table 1.

(Electric field induced strain)
Electric field induced strain (ppm) at 25 ° C. and 200 ° C. was measured using a piezoelectric / electrostrictive element. The electric field induced strain is an electric field induced strain parallel to the electric field application direction (33 directions) when a voltage of 4000 V / mm is applied to the gold electrodes on both main surfaces of the piezoelectric / electrostrictive element (S4000). Was measured with a laser displacement meter (an evaluation system manufactured by aixACCT).

(Comparative Example 1)
A piezoelectric / electrostrictive ceramics sintered body was produced in the same manner as in Example 1 except that the orientation control in Example 1 was not performed when the piezoelectric / electrostrictive ceramics sintered body was produced. That is, in Comparative Example 1, a sintered body was prepared by preparing a forming raw material using only the calcined powder A without using the plate-like particles B. The piezoelectric / electrostrictive ceramic sintered body of Comparative Example 1 had a defect of 1% or more as in Example 1, but the degree of orientation was 5% because the orientation was not controlled.

(Comparative Example 2)
The same method as in Example 1 except that the raw material powder was weighed as shown in Table 1 to prevent defects in the sintered body when the piezoelectric / electrostrictive ceramic sintered body was produced. Thus, a piezoelectric / electrostrictive ceramic sintered body was produced. In the piezoelectric / electrostrictive ceramic sintered body of Comparative Example 2, the degree of orientation was 85% as in Example 1, but no defect was caused by a deviation of 1% or more from the stoichiometric composition. .

(Comparative Example 3)
The piezoelectric / electrostrictive ceramics were produced by the same method as in Example 1 except that the raw material powder similar to that in Comparative Example 2 was used and the orientation control was not performed at the time of producing the piezoelectric / electrostrictive ceramics sintered body. A sintered body was produced. The piezoelectric / electrostrictive ceramic sintered body of Comparative Example 3 had no defects due to a deviation of 1% or more from the stoichiometric composition, and because the orientation was not controlled, the degree of orientation was 10%. It was.

(Example 2)
In Example 2, a BNT-NKT-BK-based piezoelectric / electrostrictive ceramic sintered body was produced, and a piezoelectric / electrostrictive element was produced using this piezoelectric / electrostrictive ceramic sintered body.

[Preparation of sintered piezoelectric / electrostrictive ceramics]
In producing a piezoelectric / electrostrictive ceramic sintered body, Bi ₂ O ₃ (bismuth oxide), TiO ₂ (titanium oxide), Na ₂ CO ₃ (sodium carbonate), K ₂ CO ₃ (potassium carbonate), and BaCO ₃ (carbonic acid). The raw material powder of barium) was weighed so as to have the composition shown in Table 2.

  The composition of the raw material powder is represented by the general formula xBNT-yBKT-zBT (x + y + z = 1), and the content ratios x, y, z of BNT, BKT and BT are “x” and “y” in Table 2. And from the stoichiometry shown in the column of “z”, a composition in which Bi, Na, and K are made deficient (that is, a defect is generated). The defect amounts from the stoichiometry of Bi, Na, and K are shown in the columns of “Bi defect amount (%)”, “Na defect amount (%)”, and “K defect amount (%)” in Table 2, respectively. ing. In addition, each defect amount shows each deviation | shift amount (%) in the molar conversion from a stoichiometric composition. In the column of “Defect amount (%)” in Table 2, the total amount p + q + r of the defect amounts p, q, and r from the stoichiometry of Bi, Na, and K is shown.

  Next, the weighed raw material powder and alcohol as a dispersion medium were enclosed in a wide-mouth bottle together with silicon nitride balls as grinding media, and mixed and ground for 1 hour using a planetary ball mill. Thereafter, ethanol was removed from the slurry by evaporation to obtain a mixed raw material.

  Next, the obtained mixed raw material was calcined at 1000 ° C. to obtain a calcined raw material. The time for maintaining the maximum temperature was 4 hours.

  Next, the obtained calcined raw material is enclosed in a wide-mouthed jar together with alcohol as a dispersion medium and silicon nitride balls as a pulverizing medium, and pulverized for 1 hour using a planetary ball mill, and then baked with piezoelectric / electrostrictive ceramics. A calcined powder (hereinafter referred to as “calcined powder C”) was obtained as a raw material for ligation. Using a portion of the obtained calcined powder C, molding is performed by the doctor blade method in the same manner as in Example 1 to obtain a molded body with a controlled degree of orientation, and the obtained molded body is fired. Further, pulverization was performed to produce plate-like particles (hereinafter referred to as “plate-like particles D”).

  Next, a mixture of equal amounts of toluene and isopropanol as a dispersion medium, the calcined powder C, the plate-like particles D, and polyvinyl butyral as a binder (product surface “BM-2” manufactured by Sekisui Chemical Co., Ltd.) Then, a plasticizer (dioctyl phthalate (DOP) manufactured by Kurokin Kasei Co., Ltd.) and a dispersant (trade name “SP-O30” manufactured by Kao Co., Ltd.) were mixed to prepare a slurry-like molding raw material. The amount of each raw material used was 30 parts by mass of the plate-like particles D, 100 parts by mass of the dispersion medium, 10 parts by mass of the binder, 4 parts by mass of the plasticizer, and 2 parts by mass of the dispersant with respect to 100 parts by mass of the calcined powder C.

  Next, the obtained forming raw material was stirred and degassed under reduced pressure to prepare a viscosity of 2.5 to 3.0 Pa · s. The viscosity of the molding material was measured with an LVT viscometer manufactured by Brookfield. The obtained forming raw material was formed into a flat plate shape by a doctor blade method so that the plate-like particles D were oriented in one direction and the thickness after drying was 100 μm.

  A plurality of the obtained molded bodies were laminated and press-molded into a disk shape having a diameter of 18 mm and a plate thickness of 5 mm. In press molding, uniaxial pressure molding was performed at a pressure of 15 MPa. Furthermore, CIP molding was performed on the molded body at a pressure of 100 MPa.

  Next, the compact was fired at 1170 ° C. The time for maintaining the maximum temperature was 4 hours. The obtained piezoelectric / electrostrictive ceramic sintered body was processed into a rectangular shape having a long side of 12 mm, a short side of 3 mm, and a thickness of 1 mm, and heat-treated at 700 to 1000 ° C. The XRD diffraction pattern of the obtained piezoelectric / electrostrictive ceramic sintered body was measured, and the degree of orientation of the C / axis of the piezoelectric / electrostrictive ceramic sintered body by the Lotgering method (ie, (100 ) Surface orientation degree). Table 2 shows the degree of orientation of the piezoelectric / electrostrictive ceramic sintered body of Example 2. The degree of orientation of the piezoelectric / electrostrictive ceramic sintered body of Example 2 was 80%.

[Preparation of piezoelectric / electrostrictive element]
Next, gold electrodes were formed by sputtering on both principal surfaces of the obtained piezoelectric / electrostrictive ceramics sintered body to produce a piezoelectric / electrostrictive element. The planar shape of the gold electrode film is circular, and its diameter is 1 mm. The electric field induced strain of the obtained piezoelectric / electrostrictive element was measured. Table 2 shows the results.

(Comparative Example 4)
A piezoelectric / electrostrictive ceramics sintered body was produced in the same manner as in Example 2 except that the orientation control in Example 2 was not performed when the piezoelectric / electrostrictive ceramics sintered body was produced. That is, in Comparative Example 4, a sintered body was prepared by preparing a forming raw material using only the calcined powder C without using the plate-like particles D. The piezoelectric / electrostrictive ceramic sintered body of Comparative Example 4 had a defect of 1% or more as in Example 2, but the degree of orientation was 10% because the orientation was not controlled.

(Comparative Example 5)
The same method as in Example 2 except that the raw material powder was weighed as shown in Table 2 so as not to cause defects in the sintered body when the piezoelectric / electrostrictive ceramic sintered body was produced. Thus, a piezoelectric / electrostrictive ceramic sintered body was produced. The piezoelectric / electrostrictive ceramic sintered body of Comparative Example 5 had an orientation degree of 80% as in Example 2, but no defect was caused by a deviation of 1% or more from the stoichiometric composition. .

(Comparative Example 6)
Piezoelectric / electrostrictive ceramics were produced in the same manner as in Example 2 except that the raw material powder similar to that in Comparative Example 5 was used and the orientation control was not performed during the production of the piezoelectric / electrostrictive ceramics sintered body. A sintered body was produced. The piezoelectric / electrostrictive ceramic sintered body of Comparative Example 6 had no defects due to a deviation of 1% or more from the stoichiometric composition, and because the orientation was not controlled, the degree of orientation was 5%. It was.

(result)
As shown in Tables 1 and 2, the piezoelectric / electrostrictive elements of Examples 1 and 2 have improved electric field induced strain (S4000) compared to the piezoelectric / electrostrictive elements of Comparative Examples 1-6. there were.

  From the above results, it was confirmed that the piezoelectric / electrostrictive ceramics sintered body and the piezoelectric / electrostrictive element of the present invention are superior in electric field induced strain compared with the conventional piezoelectric / electrostrictive ceramics sintered body. It was. In addition, according to the piezoelectric / electrostrictive ceramic sintered body and the piezoelectric / electrostrictive element of the present invention, the temperature dependency of the electric field induced strain characteristic at 300 ° C. or less can be improved. Further, in the above embodiment, an example in which a piezoelectric / electrostrictive ceramic sintered body is manufactured by the TGG method has been described. However, the method for manufacturing a piezoelectric / electrostrictive ceramic sintered body of the present invention is the same as the above-described manufacturing method. There is no limitation, and the same effect can be obtained by the RTGG method, the hot forge method, the magnetic field orientation method, and the like.

  The piezoelectric / electrostrictive ceramic sintered body of the present invention exhibits an excellent electric field induced strain, and is suitably used as a material of a piezoelectric / electrostrictive element (piezoelectric / electrostrictive body) constituting an actuator, a sensor or the like. The

1, 21, 31: substrate, 2, 22, 23: piezoelectric / electrostrictive body, 4, 5, 24, 25, 26: electrode, 10, 30, 40: piezoelectric / electrostrictive element, 32: laminate, 402 : Piezoelectric / electrostrictive film, 404: internal electrode film, 406: first internal electrode film, 408: second internal electrode film, 416, 418: external electrode film, 412 and 414: end face.

Claims (5)

Made of lead-free piezoelectric / electrostrictive material,
The ratio of at least one metal component of the metal components constituting the lead-free piezoelectric / electrostrictive material is a defect that has shifted by 1% or more in terms of mole from the stoichiometric composition,
A piezoelectric / electrostrictive ceramic sintered body having an orientation degree of C axis measured by the Lotgering method of 30% or more. 2. The piezoelectric / electrostrictive ceramic sintered body according to claim 1, wherein the lead-free piezoelectric / electrostrictive material has a perovskite structure represented by the following general formula (1).
ABO ₃ (1)
(However, A represents an A site constituent element and B represents a B site constituent element)   The A site constituent element includes at least one selected from the group consisting of Li, Na, K, Bi, and Ba, and the B site constituent element includes Nb, Ta, Sb, Ti, and Fe. The piezoelectric / electrostrictive ceramic sintered body according to claim 2, comprising at least one selected from the group.   The piezoelectric / electrostrictive ceramic sintered body according to any one of claims 1 to 3, wherein the degree of orientation of the C axis measured by the Lotgering method is 70 to 92%. A film-like piezoelectric / electrostrictive body comprising the piezoelectric / electrostrictive ceramic sintered body according to any one of claims 1 to 4, and
A pair of electrodes disposed across the piezoelectric / electrostrictive body;
A piezoelectric / electrostrictive element comprising: a substrate bonded to one surface of the pair of electrodes.

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