JP2011213580A - Piezoelectric/electrostrictive sintered compact, and piezoelectric/electrostrictive element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lead-free piezoelectric/electrostrictive sintered compact which exhibits a high distortion rate even under the application of a high electric field as well as a low electric field.SOLUTION: The piezoelectric/electrostrictive sintered compact 1 is obtained by firing a composition comprising: a first component including a first perovskite type oxide expressed by general formula (1): {Li(NaK)}(NbTaSb)O, a compound of one or more kinds of selective elements selected from a group consisting of Ba, Sr, Ca, La, Ce, Nd, Sm, Dy, Ho and Yb, and an Mn compound; a second component as a second perovskite type oxide expressed by general formula (2): {Ba(KNa)}(ZrNb)O; and a third component including Zn as the main component. The content of the third component in the sintered compact lies in a range where a different phase derived from Zn in the sintered compact is not caused, and also, the a, x, y, z, w, p and t satisfy prescribed conditions in the sintered body.

Description

  The present invention relates to a sintered body of a piezoelectric / electrostrictive porcelain composition (hereinafter referred to as “piezoelectric / electrostrictive sintered body”) and a piezoelectric / electrostrictive element comprising the piezoelectric / electrostrictive sintered body. .

  When used as a piezoelectric / electrostrictive body, the piezoelectric / electrostrictive sintered body has the advantage that the displacement can be precisely controlled on the order of submicrons. In particular, a piezoelectric / electrostrictive actuator using a piezoelectric / electrostrictive sintered body as a piezoelectric / electrostrictive body has high electromechanical conversion efficiency in addition to being able to precisely control displacement as described above. Since it has the advantages of high power, fast response speed, high durability, and low power consumption, it is used in a wide range of applications such as inkjet printer heads and diesel engine injectors.

  As a composition for such a piezoelectric / electrostrictive sintered body, a lead zirconate titanate (PZT) -based piezoelectric / electrostrictive porcelain composition has been conventionally used. Since the impact of lead elution on the global environment has become a strong concern, there is a concern that the use of lead, the main element of PZT-based piezoelectric / electrostrictive porcelain compositions, will be regulated in the future. Yes.

  Therefore, as shown in Non-Patent Documents 1 to 3, various piezoelectric / electrostrictive porcelain compositions including alkali niobate are used as lead-free piezoelectric / electrostrictive porcelain compositions not containing lead. However, the piezoelectric / electrostrictive characteristics of the sintered body obtained using these lead-free piezoelectric / electrostrictive porcelain compositions are not comparable to the PZT-based piezoelectric / electrostrictive sintered body, There is a need for improvement.

  The high piezoelectric / electrostrictive characteristics of PZT-based piezoelectric / electrostrictive sintered bodies are that tetragonal lead titanate (PT) and rhombohedral lead zirconate (PZ) are on the order of nanometers. It is said to be caused by a structure having a crystal phase boundary (MPB) that is dispersed as a fine phase (hereinafter referred to as “nanodispersion”).

  On the other hand, a piezoelectric / electrostrictive sintered body obtained by using the above-mentioned alkali niobate-based piezoelectric / electrostrictive porcelain composition has a structure having tetragonal and orthorhombic MPB. In addition, it is considered that the piezoelectric / electrostrictive characteristics are inferior to those of the PZT-based piezoelectric / electrostrictive sintered body. That is, even in a lead-free piezoelectric / electrostrictive sintered body, if a MPB of tetragonal and rhombohedral crystals can be formed, a high piezoelectric / electrostrictive comparable to a PZT-based piezoelectric / electrostrictive sintered body is obtained. It is expected that characteristics can be obtained.

For example, Patent Document 1 discloses that a combination of (Na, K) NbO ₃ — (Bi, Li) TiO ₃ that is tetragonal and (Na, K) NbO ₃ —BaZrO ₃ that is rhombohedral is a PZT system. It is disclosed that a high piezoelectric constant (d ₃₃ = 420 pC / N) comparable to that of the piezoelectric / electrostrictive sintered body can be achieved.

Non-Patent Document 4 discloses a PZT-based piezoelectric / electrostrictive sintered body in a combination of tetragonal (Ba, Ca) TiO ₃ and rhombohedral Ba (Ti, Zr) O _3. It has been reported that high piezoelectric constants (d ₃₃ = 560-620 pC / N) can be achieved. In addition, the temperature characteristic in the range of 20 to 70 ° C. is also flat and desirable.

  As described above, by forming MPBs of tetragonal crystals and rhombohedral crystals, piezoelectric / electrostrictives more than PZT piezoelectric / electrostrictive sintered bodies can be obtained even in lead-free piezoelectric / electrostrictive sintered bodies. The possibility of achieving the characteristics has been suggested.

  However, in the lead-free piezoelectric / electrostrictive sintered bodies having tetragonal and rhombohedral MPBs obtained so far, a high level of piezoelectric constant is achieved in a low electric field. The distortion rate in a high electric field is unknown (Patent Document 1 and Non-Patent Document 4). Specifically, although a high strain rate that surpasses PZT-based piezoelectric / electrostrictive sintered bodies has been achieved at a low electric field (0.5 kV / mm), a high electric field (for example, It is expected that an increase in distortion rate at about 4 kV / mm) cannot be expected (Non-Patent Document 4).

  In the configuration described in Non-Patent Document 4, the Curie temperature (Tc) is low (93 ° C.), which is impractical. Further, in this configuration, since a high firing temperature (1000 to 1300 ° C. in the configuration described in Patent Document 1, 1450 to 1500 ° C. in the configuration described in Non-Patent Document 4) is required, the piezoelectric / electrostrictive ceramic When the composition is fired to form a film, there is a concern about a change in the composition due to volatilization of some components, reaction with the substrate, or the like, an increase in energy consumption in the manufacturing process of the sintered body, and the like.

International Publication No. 2008/143160

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) W. Liu et al. , Phys Rev. Lett. 103, 257602 (2009)

  The object of the present invention is to solve the above-mentioned problems. While maintaining a practical Curie temperature (specifically, 200 ° C. or higher), not only when a low electric field is applied, but also when a high electric field is applied. The object is to provide a lead-free piezoelectric / electrostrictive sintered body that sometimes exhibits a high electric field induced strain rate. Another object of the present invention is to provide a piezoelectric / electrostrictive element comprising such a piezoelectric / electrostrictive sintered body.

The above purpose is
The first perovskite oxide represented by the general formula (1) {Li _y (Na _1−x K _x ) _1−y } _a (Nb _1−z−w Ta _z Sb _w ) O ₃ , Ba, Sr A first component comprising a compound of one or more selective elements selected from the group consisting of Ca, La, Ce, Nd, Sm, Dy, Ho and Yb, and a compound of Mn,
A second component that is a second perovskite oxide represented by the general formula (2) {Ba _t (K _p Na _1-p ) _1-t } (Zr _t Nb _1-t ) O ₃ , and Zn A third component as a main component,
A piezoelectric / electrostrictive sintered body obtained by firing a composition comprising
In the piezoelectric / electrostrictive sintered body, the content of the third component is in a range that does not cause a Zn-derived heterogeneous phase in the piezoelectric / electrostrictive sintered body, and in the composition of the piezoelectric / electrostrictive sintered body ,
In the general formula (1), a, x, y, z and w are 1 <a ≦ 1.1, 0.30 ≦ x ≦ 0.70, 0.02 ≦ y ≦ 0.10, 0, respectively. ≦ z ≦ 0.5 and 0.01 ≦ w ≦ 0.1 are satisfied,
In the general formula (2), p and t satisfy 0 ≦ p ≦ 1 and 0 <t ≦ 0.5, respectively.
This is achieved by a piezoelectric / electrostrictive sintered body.

  The other object is achieved by a piezoelectric / electrostrictive element according to the present invention and a piezoelectric / electrostrictive element comprising at least a pair of electrodes.

  According to the present invention, a lead-free piezoelectric / electrostrictive sintered body that exhibits a high electric field induced strain rate not only when a low electric field is applied but also when a high electric field is applied while maintaining a practical Curie temperature, and such A piezoelectric / electrostrictive element comprising a piezoelectric / electrostrictive sintered body is provided.

It is sectional drawing of a piezoelectric / electrostrictive actuator. It is sectional drawing of a piezoelectric / electrostrictive actuator. It is sectional drawing of a piezoelectric / electrostrictive actuator. It is a perspective view of a piezoelectric / electrostrictive actuator. It is a longitudinal cross-sectional view of a piezoelectric / electrostrictive actuator. It is a cross-sectional view of a piezoelectric / electrostrictive actuator. It is a disassembled perspective view of a part of a piezoelectric / electrostrictive actuator.

1. Configuration of Piezoelectric / Electrostrictive Sintered Body According to the Present Invention The present invention includes a tetragonal component having a specific composition, a rhombohedral component having a specific composition, and a third component containing zinc as a main component, after firing When a piezoelectric / electrostrictive porcelain composition obtained by blending so that the composition satisfies a specific condition is prepared, tetragonal / rhombohedral MPB is formed in the piezoelectric / electrostrictive sintered body obtained by firing the composition. As a result, even in a lead-free piezoelectric / electrostrictive sintered body, a PZT-based piezoelectric / electrostrictive sintering is performed while having a low firing temperature, a high electric field high strain rate, and a high Curie temperature (Tc). This is based on the finding that piezoelectric characteristics that surpass the body can be achieved.

More specifically, as described above, the piezoelectric / electrostrictive sintered body according to the present invention is
The first perovskite oxide represented by the general formula (1) {Li _y (Na _1−x K _x ) _1−y } _a (Nb _1−z−w Ta _z Sb _w ) O ₃ , Ba, Sr A first component comprising a compound of one or more selective elements selected from the group consisting of Ca, La, Ce, Nd, Sm, Dy, Ho and Yb, and a compound of Mn,
A second component that is a second perovskite oxide represented by the general formula (2) {Ba _t (K _p Na _1-p ) _1-t } (Zr _t Nb _1-t ) O ₃ , and Zn A third component as a main component,
A piezoelectric / electrostrictive sintered body obtained by firing a composition comprising
In the piezoelectric / electrostrictive sintered body, the content of the third component is in a range that does not cause a Zn-derived heterogeneous phase in the piezoelectric / electrostrictive sintered body, and in the composition of the piezoelectric / electrostrictive sintered body ,
In the general formula (1), a, x, y, z and w are 1 <a ≦ 1.1, 0.30 ≦ x ≦ 0.70, 0.02 ≦ y ≦ 0.10, 0, respectively. ≦ z ≦ 0.5 and 0.01 ≦ w ≦ 0.1 are satisfied,
In the general formula (2), p and t satisfy 0 ≦ p ≦ 1 and 0 <t ≦ 0.5, respectively.
A piezoelectric / electrostrictive sintered body.

2. First Component As described above, the first component of the composition capable of obtaining the piezoelectric / electrostrictive sintered body according to the present invention by firing includes the first perovskite oxide, the compound of the selective element, And a compound of manganese (Mn).

  First, the first perovskite oxide is a perovskite oxide having a composition represented by the general formula (1), which will be described in detail later.

  Next, the compound of the selective element includes barium (Ba), strontium (Sr), calcium (Ca), lanthanum (La), cerium (Ce), neodymium (Nd), samarium (Sm), dysprosium (Dy), It is a compound of one or more elements selected from the group consisting of holmium (Ho) and ytterbium (Yb) (referred to herein as “selective elements”).

  In the first component, the atomic equivalent content of the compound of the selective element with respect to 100 mol parts of the first perovskite oxide is 0.01 mol parts or more and 0.5 mol parts or less. desirable. If the content of the compound of the selective element is below this range, the electric field induced strain when applying a high electric field tends to be small, which is not desirable. On the other hand, if the content of the compound of the selected element exceeds this range, the crystal phase changes from tetragonal to orthorhombic, which tends to reduce the electric field induced strain when a high electric field is applied, which is not desirable.

  The selective element is preferably dissolved as an oxide in the first perovskite oxide. That is, it is desirable that the selective element is taken into the crystal lattice of the first perovskite oxide that is a parent phase and exists in the sintered body as an element constituting the parent phase. However, the heterogeneous phase containing the selective element may be slightly present inside the sintered body.

  Further, it is desirable that Mn derived from the Mn compound is dissolved as an oxide in the first perovskite oxide, but it is preferable that the Mn compound is a solid boundary solution or a second perovskite oxidation described later. It may be dissolved as an oxide in the product.

  In addition, in the first component in the piezoelectric / electrostrictive sintered body after firing, the content of the Mn compound in terms of Mn atom with respect to 100 mol parts of the first perovskite oxide is 5 mol parts or less. It is desirable to be. When the content of the Mn compound exceeds this range, the dielectric loss increases, and the electric field induced strain when applying a high electric field tends to be small, which is not desirable. More preferably, the content of the Mn compound in terms of Mn atoms with respect to 100 mol parts of the first perovskite oxide is 3 mol parts or less.

  Further, a very small amount of the Mn compound is sufficient. For example, even when only 0.001 mole part of Mn compound in terms of Mn atom is contained per 100 mole parts of the first perovskite oxide, the sintered body can be easily polarized. Due to the synergistic effect with the substitution by Sb, the electric field induced strain at the time of applying a high electric field increases.

3. On the other hand, as described above, the second component of the composition capable of obtaining the piezoelectric / electrostrictive sintered body according to the present invention by firing has a composition represented by the general formula (2). The second perovskite oxide will be described in detail later.

4). Third Component Furthermore, the third component of the composition capable of obtaining the piezoelectric / electrostrictive sintered body according to the present invention by firing contains zinc (Zn) as a main component as described above.

5. The ratio of the first and second perovskite oxides The ratio of the second perovskite oxide to the total sum of the first and second perovskite oxides is the ratio of the composition It is necessary to be within a range where firing is possible. Specifically, the ratio is appropriately adjusted according to the composition of the first perovskite oxide and the second perovskite oxide, and the composition is fired by a phenomenon such as an optimum firing temperature increasing. Therefore, it is necessary to avoid a situation where it is difficult to obtain a desired sintered body.

  In one embodiment of the present invention, the ratio of the second perovskite oxide to the sum of the first perovskite oxide and the second perovskite oxide is the piezoelectric / electrostrictive firing after firing. It is desirable that the composition is 10 mol% or more and less than 80 mol% as a composition of the bonded body. When the ratio is less than 10 mol%, it is not desirable (because it is difficult to produce a tetragonal / rhombohedral mixed crystal state and it is difficult to achieve desired piezoelectric / electrostrictive characteristics). Conversely, when the ratio is 80 mol% or more, it is difficult to obtain the desired sintered body by firing the composition due to a phenomenon such as an increase in the optimum firing temperature. More preferably, the ratio is 20 mol% or more and less than 70 mol%.

6). The content of the third component The content of the third component (including Zn as a main component) in the piezoelectric / electrostrictive sintered body does not cause a Zn-derived heterogeneous phase in the piezoelectric / electrostrictive sintered body. Must be in range. When a heterogeneous phase derived from Zn occurs in the piezoelectric / electrostrictive sintered body, problems such as deterioration of dielectric loss and deterioration of piezoelectric / electrostrictive characteristics occur. Therefore, the composition of the first perovskite oxide and the second perovskite oxide and the second perovskite oxide with respect to the sum of the first perovskite oxide and the second perovskite oxide. It is necessary that the content of the third component in the piezoelectric / electrostrictive sintered body is appropriately adjusted in accordance with the ratio of the piezoelectric / electrostrictive sintered body so that a Zn-derived heterogeneous phase does not occur in the piezoelectric / electrostrictive sintered body. It is.

  In another embodiment of the present invention, the content of the third component in the sintered piezoelectric / electrostrictive sintered body after firing is 0.01 mol% or more and less than 3.00 mol% in terms of Zn atoms. Is desirable. When the content is less than 0.01 mol%, the distortion rate when a high electric field is applied becomes insufficient, which is not desirable. On the contrary, when the content is 3.00 mol% or more, a heterogeneous phase derived from Zn occurs in the sintered piezoelectric / electrostrictive sintered body, and there are problems such as deterioration of dielectric loss and deterioration of piezoelectric / electrostrictive characteristics. This is undesirable because it occurs. More preferably, the content is 0.01 mol% or more and less than 1.00 mol% in terms of Zn atoms.

7). The composition of the first perovskite oxide By the way, the general formula (1) (that is, {Li _y (Na _1−x K _x ) _1−y } _a (Nb _1−z−w Ta _z Sb _w ) O ₃ ) In the first perovskite oxide represented by the following formula: a, x, y, z and w are 1 <a ≦ 1.1, respectively, as the composition of the piezoelectric / electrostrictive sintered body after firing. It is necessary to satisfy 0.30 ≦ x ≦ 0.70, 0.02 ≦ y ≦ 0.10, 0 ≦ z ≦ 0.5, and 0.01 ≦ w ≦ 0.1.

  The “a” is a parameter corresponding to the stoichiometric ratio of the A site to the B site in the tetragonal crystal derived from the first component. In the piezoelectric / electrostrictive sintered body according to the present invention, 1 <a ≦ By strictly controlling the parameters so as to satisfy 1.1, desired piezoelectric / electrostrictive characteristics are achieved. Specifically, in the range of a ≦ 1, the sintering temperature at which the sintered body is sufficiently densified becomes high and the alkali component is likely to evaporate. As a result, the composition of the sintered body is likely to fluctuate. This is not desirable. Also, from the viewpoint of manufacturing cost reduction and energy saving, it is not desirable to raise the firing temperature. On the contrary, in the range of 1.1 <a, the dielectric loss of the resultant sintered body is increased, and the electric field induced strain when a high electric field is applied cannot be increased, which is not desirable. More preferably, it is desirable to be in the range of 1.00 <a ≦ 1.05.

  Next, “x” represents the presence of K in a metal element (specifically, potassium (K) and sodium (Na)) that is not Li (lithium) at the A site in the tetragonal crystal derived from the first component. The “y” represents the abundance ratio (molar ratio) of Li to metal elements (K and Na) that are not lithium (Li) at the A site in the tetragonal crystal derived from the first component. It is a parameter. In the piezoelectric / electrostrictive sintered body according to the present invention, by strictly controlling the parameters so as to satisfy 0.30 ≦ x ≦ 0.70 and 0.02 ≦ y ≦ 0.10, a desired value can be obtained. Piezoelectric / electrostrictive properties are achieved.

  Specifically, in the range of x <0.30, the electric field induced strain at the time of applying a high electric field of the resultant sintered body is rapidly reduced, which is not desirable. On the other hand, in the range of 0.70 <x, the firing temperature at which the sintered body is sufficiently densified becomes high, and as a result, the composition of the sintered body is likely to fluctuate. This is not desirable because problems such as an increase occur. On the other hand, in the range of y <0.02, the firing temperature at which the sintered body is sufficiently densified becomes high and the above-described problems occur, which is not desirable. On the contrary, in the range of 0.10 <y, the resulting sintered body contains a large number of different phases, which is not desirable because the insulating properties of the sintered body are lowered. More preferably, it is desirable to be in the range of 0.04 ≦ y ≦ 0.08.

  The “z” represents the abundance ratio (molar ratio) of Ta (tantalum) in the total metal elements of the B site in the tetragonal crystal derived from the first component, and the “w” is derived from the first component. Is a parameter representing the abundance ratio (molar ratio) of antimony (Sb) in the total metallic elements at the B site in tetragonal crystals. In the piezoelectric / electrostrictive sintered body according to the present invention, the desired piezoelectric / electrostrictive sintered body is controlled by strictly controlling the parameters so as to satisfy 0 ≦ z ≦ 0.5 and 0.01 ≦ w ≦ 0.1. Electrostrictive properties are achieved.

Specifically, in the range of 0.5 <z, the firing temperature at which the sintered body becomes sufficiently dense becomes high, which is not desirable. More preferably, it is desirable that the range is 0 ≦ z ≦ 0.3. On the other hand, in the range of 0.1 <w, the tetragonal to orthorhombic phase transition temperature (hereinafter referred to as “phase transition temperature”) _TOT moves away from room temperature, and the electric field induced strain when a high electric field is applied is reduced. Not desirable. More preferably, it is desirable to be in the range of 0.02 ≦ w ≦ 0.08. Incidentally, the phase transition temperature _TOT is preferably 50 ° C. or lower, and more preferably 10 ° C. or lower.

8). The composition whereas the second perovskite-type oxide, the represented by the general formula (2) (i.e. _{{Ba t (K p Na 1} -p) 1-t} (Zr t Nb 1-t) O 3) In the second perovskite-type oxide, p and t must satisfy 0 ≦ p ≦ 1 and 0 <t ≦ 0.5, respectively, as the composition of the sintered piezoelectric / electrostrictive sintered body.

  The “p” represents an abundance ratio (molar ratio) of K in a metal element (specifically, K and Na) that is not Ba at the A site in the rhombohedral crystal derived from the second component, and the “t” ”Means the abundance ratio (molar ratio) of barium (Ba) in the total metal element at the A site in the rhombohedral crystal derived from the second component and the total metal element at the B site (specifically, zirconium (Zr) and This is a parameter representing the abundance ratio (molar ratio) of Zr in niobium (Nb). In the piezoelectric / electrostrictive sintered body according to the present invention, the desired piezoelectric / electrostrictive characteristics can be obtained by strictly managing the parameters so as to satisfy 0 ≦ p ≦ 1 and 0 <t ≦ 0.5. Achieved.

  Specifically, the metal element that is not Ba at the A site in the rhombohedral crystal derived from the second component may be either K or Na, or both of them. In this case, the abundance ratio (molar ratio) between K and Na is not particularly limited. On the other hand, in the range of 0.5 <t, the second component becomes cubic at room temperature, which is not desirable. More preferably, it is desirable that 0 <t ≦ 0.4.

9. Manufacturing Method of Piezoelectric / Electrostrictive Sintered Body According to the Present Invention The piezoelectric / electrostrictive sintered body according to the present invention is manufactured by a general method well known to those skilled in the art as a manufacturing method of a piezoelectric / electrostrictive sintered body. Can do. That is, the manufacturing method described below is an example of a method for manufacturing a piezoelectric / electrostrictive sintered body according to the present invention, and the technical scope of the present invention is not limited to the following manufacturing method.

(1) Production of raw material powder First, a raw material powder of a piezoelectric / electrostrictive porcelain composition for producing a piezoelectric / electrostrictive sintered body according to the present invention is prepared as follows. The raw materials containing the constituent elements (Li, Na, K, Nb, Ta, Sb, etc.) of each perovskite oxide are weighed and mixed so as to satisfy a predetermined molar ratio of the constituent elements. The mixing method is not particularly limited, and mortar mixing, ball mill, pot mill, bead mill, hammer mill, jet mill and the like are used. As the raw material of the constituent element of the perovskite oxide, an oxide or a compound such as carbonate or tartrate that becomes an oxide in the calcination process is used. A dispersion medium (for example, an organic solvent) may be added to the raw material during mixing. As the dispersion medium, an organic solvent such as ethanol, toluene, or acetone is used. When the solvent is not added during mixing, the mixed raw material powder is obtained as it is by mixing. However, when the solvent is added during mixing, the dispersion medium is removed from the obtained mixed slurry by evaporation, filtration, etc. The mixed raw material obtained is obtained.

  The dried mixed raw material is calcined at 400 to 1300 ° C. to synthesize a perovskite oxide powder. The calcination may be performed only once or may be performed twice or more. When performing calcination twice or more, the conditions of each calcination may be the same or different. The atmosphere at the time of calcination may be an air atmosphere or an oxygen atmosphere. The temperature raising rate and the temperature lowering rate during calcination are desirably 20 to 2000 ° C./hour, and the time for maintaining the calcination temperature is desirably 30 seconds to 20 hours.

The powder of the mixed raw material can be calcined by a commonly used one-stage calcining schedule (trapezoidal temperature profile). For example,
[1] A first stage in which the temperature is raised from room temperature to a first calcination temperature of 800 to 1000 ° C. at a temperature increase rate of 20 to 2000 ° C./hour to maintain the first calcination temperature;
The mixed raw material powder is calcined by a one-stage calcining schedule in which the temperature is lowered to room temperature at a temperature lowering rate of 20 to 2000 ° C./hour immediately after the completion of the step.

Further, the mixed raw material powder may be calcined in a multi-stage calcining schedule. For example,
[1] a first stage in which the temperature is raised from room temperature to a first calcining temperature of 400 to 800 ° C. and maintained at the first calcining temperature; and [2] the first calcining temperature to the second calcining A second stage of raising the temperature to 800-1000 ° C. and maintaining the second calcining temperature;
The powder of the mixed raw material is calcined by a two-stage calcining schedule in which the temperature is lowered to room temperature after the completion of.

Or
[1] a first stage in which the temperature is raised from room temperature to a first calcining temperature of 900 to 1300 ° C. at a heating rate of 500 ° C./hour or more to maintain the first calcining temperature; and [2] first A second stage in which the temperature is lowered at a temperature lowering rate of 200 ° C./hour or more from the calcining temperature of 600 to 1000 ° C. of the second calcining temperature to maintain the second calcining temperature;
The powder of the mixed raw material is calcined by a two-stage calcining schedule in which the temperature is lowered to room temperature after the completion of.
Furthermore, the powder of the mixed raw material may be calcined by a three-stage calcining schedule obtained by combining the above two-stage calcining schedules.

  The synthesized perovskite oxide powder may be pulverized and classified to adjust the particle size of the perovskite oxide powder to a desired size. When pulverization is performed, pulverization methods such as mortar pulverization, pot mill, bead mill, hammer mill, jet mill, mesh or screen pressing are used.

  Alternatively, the perovskite oxide powder may be synthesized by an alkoxide method or a coprecipitation method instead of a solid phase reaction method. The first perovskite type oxide (tetragonal crystal) and the second perovskite type oxide (rhombohedral crystal) were separately synthesized and then mixed at a predetermined ratio and fired. May be. Further, for each perovskite type oxide, a solid solution of B site elements (for example, a composite oxide of a plurality of B site elements) is synthesized in advance, and then mixed with the A site element and calcined perovskite type oxide. Powders may be synthesized.

  The average particle diameter of the perovskite oxide powder is preferably 0.07 to 3 μm, and more preferably 0.1 to 1 μm. In order to adjust the particle size of the perovskite oxide powder, the perovskite oxide powder may be heat-treated at 400 to 850 ° C. Finer particles are easier to be integrated with other particles. Therefore, when this heat treatment is performed, a perovskite oxide powder having a uniform particle size is obtained, and a sintered body having a uniform particle size is obtained.

  In the first component, a powder of a raw material of a compound of a selective element and a compound of Mn is added to the powder of the first perovskite oxide. In addition, the piezoelectric / electrostrictive porcelain composition for producing the piezoelectric / electrostrictive sintered body according to the invention includes Zn in addition to the first component and the second component (the second perovskite oxide). A third component containing as a main component. Addition of the compound of the selective element, the compound of Mn, and the powder of the raw material of the third component is, for example, the powder of the perovskite oxide synthesized as described above, the compound of the selective element, the compound of Mn, and the third component The raw material powder can be weighed and mixed so as to satisfy a predetermined molar ratio of the constituent elements. The mixing method is not particularly limited, and mortar mixing, ball mill, pot mill, bead mill, hammer mill, jet mill and the like are used. A dispersion medium may be added to the raw material during mixing. As the dispersion medium, for example, an organic solvent such as ethanol, toluene, or acetone is used. When the solvent is not added during mixing, the mixed raw material powder is obtained as it is by mixing. However, when the solvent is added during mixing, the dispersion medium is removed from the obtained mixed slurry by evaporation, filtration, etc. The mixed raw material obtained is obtained.

As a raw material for the compound of the selective element and the compound of Mn, an oxide or a compound such as carbonate or tartrate that becomes an oxide in the firing process is used. As a raw material of Mn, tetravalent manganese dioxide (MnO ₂ ) having a valence of Mn or divalent manganese carbonate (MnCO ₃ ) is mainly used.

  The addition of the raw material powder of the selected element compound, the Mn compound, and the third component (hereinafter may be collectively referred to as “minor component”) is suitable before the firing step described below. Can be performed at a suitable timing (for example, after calcination of the perovskite oxide powder).

(Production of sintered body of piezoelectric / electrostrictive porcelain composition)
In the production of the sintered body of the piezoelectric / electrostrictive porcelain composition according to the present invention, the above-mentioned perovskite oxide powder and the minor component powder are weighed so as to satisfy a predetermined molar ratio of the constituent elements. , Mix. The mixing method is not particularly limited, and mortar mixing, ball mill, pot mill, bead mill, hammer mill, jet mill and the like are used. A dispersion medium may be added to these powders during mixing. As the dispersion medium, for example, an organic solvent such as ethanol, toluene, or acetone is used. When the solvent is not added during mixing, the mixed raw material powder is obtained as it is by mixing. However, when the solvent is added during mixing, the dispersion medium is removed from the obtained mixed slurry by evaporation, filtration, etc. The mixed raw material obtained is obtained.

  The obtained mixed raw material (hereinafter, the raw material may be referred to as “composite raw material powder”) is first formed into a raw material powder by press molding, tape molding, casting molding, or the like and fired. The firing temperature of the obtained raw material powder compact is desirably 600 to 1300 ° C. The atmosphere during firing may be an air atmosphere or an oxygen atmosphere. Alternatively, firing may be performed in a state in which an atmosphere adjusting powder composed of the same element as the element contained in the composite raw material powder is placed around the composite raw material powder. The temperature raising rate and the temperature lowering rate during firing are desirably 20 to 2000 ° C./hour, and the time for maintaining the firing temperature is desirably 30 seconds to 10 hours.

It is also desirable to include a small amount of sintering aid in the composite raw material powder. The sintering aid is preferably an oxide containing Li, Li ₂ O, Li ₂ O ₂ , LiNbO ₃ , Li ₃ NbO ₄ , LiTaO ₃ , Li ₃ TaO ₄ , LiSbO ₃ , Li ₃ SbO ₄ , It is more desirable that it is at least one selected from the group consisting of Li (Nb, Ta, Sb) O ₃ and Li ₃ (Nb, Ta, Sb) O ₄ . When a sintering aid is contained in the composite raw material powder, the sintered density of the sintered body of the piezoelectric / electrostrictive porcelain composition is improved.

The molded body of the composite raw material powder is fired on a commonly used firing schedule. For example,
[1] A first stage in which the temperature is raised from room temperature to a first firing temperature of 950 to 1300 ° C. at a heating rate of 20 to 2000 ° C./hour and the first firing temperature is maintained;
Immediately after the completion of the above, firing is performed according to a one-stage firing schedule (trapezoidal temperature profile) in which the temperature is lowered to room temperature at a rate of temperature reduction of 20 to 2000 ° C./hour.

Alternatively, the molded body of the composite raw material powder is fired according to the following multi-stage firing schedule. For example,
[1] A first stage of raising the temperature from room temperature to a first firing temperature of 600 to 950 ° C. and maintaining the first firing temperature; and [2] 950 to 950 of the second firing temperature from the first firing temperature. A second stage of raising the temperature to 1300 ° C. and maintaining the second firing temperature;
After completion of the step, the composite raw material powder compact is fired according to a two-stage firing schedule in which the temperature is lowered to room temperature.

Alternatively, the molded body of the composite raw material powder is
[1] a first stage in which the temperature is raised from room temperature to a first firing temperature of 1000 to 1300 ° C. at a heating rate of 500 ° C./hour or more to maintain the first firing temperature; and [2] first firing A second stage in which the temperature is lowered from a temperature to a second firing temperature of 600 to 1000 ° C. at a rate of temperature fall of 200 ° C./hour or more to maintain the second firing temperature;
Is fired by a two-stage firing schedule in which the temperature is lowered to room temperature.

  The molded body of the composite raw material powder may be fired according to a three-stage firing schedule that combines the two two-stage firing schedules described above.

  In such a multi-stage firing schedule, the sintered body of the piezoelectric / electrostrictive porcelain composition is sufficiently densified, and the relative density of the sintered body of the piezoelectric / electrostrictive porcelain composition is also 90 to 95%, which is 95 to 98%. May be reached.

(Manufacture of piezoelectric / electrostrictive elements)
On the surface of the sintered body obtained as described above, at least a pair of electrodes is formed by screen printing, resistance heating vapor deposition, sputtering or the like, and the piezoelectric / electrostrictive element according to the present invention is obtained. That is, the piezoelectric / electrostrictive element according to the present invention is a piezoelectric / electrostrictive element comprising the aforementioned piezoelectric / electrostrictive sintered body according to the present invention and at least a pair of electrodes. Further, the raw material powder compact and the electrode may be integrally fired, or the electrode may be formed inside the sintered compact. Furthermore, processing such as polishing and cutting may be performed on the sintered body.

  Preferably, the sintered body on which the electrodes are formed is sequentially subjected to polarization treatment and aging treatment. The aging process may be omitted.

  When performing the polarization treatment, the sintered body on which the electrode is formed is immersed in an insulating oil such as silicon oil, and a voltage is applied to the electrode. At this time, it is desirable to perform a high temperature polarization treatment in which the sintered body is heated to 50 to 150 ° C. When performing the high temperature polarization treatment, an electric field of 2 to 10 kV / mm is applied to the sintered body.

  When performing an aging process, a sintered compact is heated in air | atmosphere to 100-300 degreeC below Curie temperature (Tc) in the state with the electrode open | released.

  The piezoelectric / electrostrictive element according to the present invention manufactured as described above can be used as a so-called actuator. Such an actuator can be used, for example, in an inkjet head in an inkjet printer. The piezoelectric / electrostrictive element can also be used as a sensor, for example.

  Accordingly, as the second to fifth embodiments according to the present invention, the configuration and manufacturing method of single-layer, multilayer, multilayer, and offset-type piezoelectric / electrostrictive actuators will be described below with reference to the drawings. explain.

(Second Embodiment)
The second embodiment relates to a single-layer piezoelectric / electrostrictive actuator 1 using the above-described piezoelectric / electrostrictive porcelain composition.

(Outline of piezoelectric / electrostrictive actuator 1)
FIG. 1 is a schematic diagram of a piezoelectric / electrostrictive actuator 1 according to a second embodiment. FIG. 1 is a sectional view of the piezoelectric / electrostrictive actuator 1.

  As shown in FIG. 1, the piezoelectric / electrostrictive actuator 1 has a structure in which an electrode film 121, a piezoelectric / electrostrictive film 122 and an electrode film 123 are laminated in this order on the upper surface of a substrate 11. The electrode films 121 and 123 on both main surfaces of the piezoelectric / electrostrictive film 122 face each other with the piezoelectric / electrostrictive film 122 interposed therebetween. The laminate 12 in which the electrode film 121, the piezoelectric / electrostrictive film 122 and the electrode film 123 are laminated is fixed to the substrate 11.

  “Fixing” refers to bonding the laminate 12 to the substrate 11 by a solid phase reaction at the interface between the substrate 11 and the laminate 12 without using an organic adhesive or an inorganic adhesive. The laminate may be bonded to the substrate by a solid phase reaction at the interface between the substrate and the piezoelectric / electrostrictive film at the bottom layer of the laminate.

  In the piezoelectric / electrostrictive actuator 1, when a voltage is applied to the electrode films 121 and 123, the piezoelectric / electrostrictive body 122 expands and contracts in a direction perpendicular to the electric field according to the applied voltage, and as a result, bending displacement occurs. Arise.

(Piezoelectric / electrostrictive film 122)
The piezoelectric / electrostrictive film 122 is a sintered body of the piezoelectric / electrostrictive ceramic composition of the first embodiment.

  The film thickness of the piezoelectric / electrostrictive film 122 is preferably 0.5 to 50 μm, more preferably 0.8 to 40 μm, and particularly preferably 1 to 30 μm. This is because if the thickness of the piezoelectric / electrostrictive film 122 falls below this range, densification tends to be insufficient. Further, if the thickness of the piezoelectric / electrostrictive film 122 exceeds this range, the shrinkage stress during sintering increases, so that it is necessary to increase the thickness of the substrate 11, and the piezoelectric / electrostrictive actuator 1 is downsized. This is because it becomes difficult.

(Electrode films 121, 123)
The material of the electrode films 121 and 123 is a metal such as platinum, palladium, rhodium, gold or silver, or an alloy thereof. Among these, platinum or an alloy containing platinum as a main component is preferable in terms of high heat resistance during firing. Depending on the firing temperature, an alloy such as silver-palladium is also preferably used.

  The film thicknesses of the electrode films 121 and 123 are desirably 15 μm or less, and more desirably 5 μm or less. This is because if the film thickness of the electrode films 121 and 123 exceeds this range, the electrode films 121 and 123 function as a relaxation layer and the bending displacement tends to be small. In addition, in order for the electrode films 121 and 123 to appropriately perform their roles, the film thickness of the electrode films 121 and 123 is desirably 0.05 μm or more.

  The electrode films 121 and 123 are desirably formed so as to cover regions that substantially contribute to the bending displacement of the piezoelectric / electrostrictive film 122. For example, it is desirable that the piezoelectric / electrostrictive film 122 is formed so as to cover a region including 80% or more of both main surfaces of the piezoelectric / electrostrictive film 122 including the central portion.

(Substrate 11)
The material of the base body 11 is ceramics, but there is no limitation on the type thereof. However, ceramics including at least one selected from the group consisting of stabilized zirconium oxide, aluminum oxide, magnesium oxide, mullite, aluminum nitride, silicon nitride and glass from the viewpoints of heat resistance, chemical stability, and insulation. It is desirable that Among these, stabilized zirconium oxide is more desirable from the viewpoint of mechanical strength and toughness. “Stabilized zirconium oxide” refers to zirconium oxide in which the phase transition of the crystal is suppressed by the addition of a stabilizer, and includes partially stabilized zirconium oxide in addition to stabilized zirconium oxide.

  Examples of the stabilized zirconium oxide include zirconium oxide containing 1 to 30 mol% of calcium oxide, magnesium oxide, yttrium oxide, ytterbium oxide, cerium oxide, or a rare earth metal oxide as a stabilizer. Among these, zirconium oxide containing yttrium oxide as a stabilizer is desirable because of its particularly high mechanical strength. The content of yttrium oxide is desirably 1.5 to 6 mol%, and more desirably 2 to 4 mol%. In addition to yttrium oxide, it is further desirable to contain 0.1 to 5 mol% of aluminum oxide. The stabilized zirconium oxide crystal phase is a mixed crystal of cubic and monoclinic, a mixed crystal of tetragonal and monoclinic, or a mixed crystal of cubic, tetragonal and monoclinic, etc. However, it is preferable from the viewpoint of mechanical strength, toughness, and durability that the main crystal phase is a mixed crystal of tetragonal crystals and cubic crystals or a tetragonal crystal.

  The plate thickness of the substrate 11 is uniform. The plate thickness of the substrate 11 is preferably 1 to 1000 μm, more preferably 1.5 to 500 μm, and particularly preferably 2 to 200 μm. This is because the mechanical strength of the piezoelectric / electrostrictive actuator 1 tends to decrease when the thickness of the substrate 11 is less than this range. Further, if the thickness of the substrate 11 exceeds this range, the rigidity of the substrate 11 increases, and the bending displacement due to expansion / contraction of the piezoelectric / electrostrictive film 122 when a voltage is applied tends to decrease.

  The surface shape of the substrate 11 (the shape of the surface to which the laminate is fixed) is not particularly limited, and may be a triangle, a rectangle (rectangle or square), an ellipse, or a circle. You may go. It is good also as a compound form which combined these basic forms.

(Manufacture of piezoelectric / electrostrictive actuator 1)
In manufacturing the piezoelectric / electrostrictive actuator 1, the electrode film 121 is formed on the substrate 11. The electrode film 121 is formed by a method such as ion beam, sputtering, vacuum deposition, PVD (Physical Vapor Deposition), ion plating, CVD (Chemical Vapor Deposition), plating, aerosol deposition, screen printing, spraying, or dipping. Among these, from the viewpoint of bondability between the substrate 11 and the piezoelectric / electrostrictive film 122, a sputtering method or a screen printing method is desirable. The formed electrode film 121 is fixed to the substrate 11 and the piezoelectric / electrostrictive film 122 by heat treatment. The temperature of the heat treatment is approximately 500 to 1400 ° C., although it varies depending on the material of the electrode film 121 and the formation method.

  Subsequently, a piezoelectric / electrostrictive film 122 is formed on the electrode film 121. The piezoelectric / electrostrictive film 122 is formed by ion beam, sputtering, vacuum deposition, PVD (Physical Vapor Deposition), ion plating, CVD (Chemical Vapor Deposition), plating, sol-gel, aerosol deposition, screen printing, spraying, dipping, etc. It is formed by the method. Among these, the screen printing method is desirable in that the accuracy of the planar shape and film thickness is high and the piezoelectric / electrostrictive film can be formed continuously.

  Subsequently, an electrode film 123 is formed on the piezoelectric / electrostrictive film 122. The electrode film 123 is formed in the same manner as the electrode film 121.

  After forming the electrode film 123, the base body 11 on which the laminate 12 is formed is integrally fired. By this firing, the piezoelectric / electrostrictive film 122 is sintered and the electrode films 121 and 123 are heat-treated. The firing temperature of the piezoelectric / electrostrictive film 122 is desirably 800 to 1250 ° C, and more desirably 900 to 1200 ° C. When the firing temperature of the piezoelectric / electrostrictive film 122 falls below this range, the piezoelectric / electrostrictive film 122 is not sufficiently densified, and the substrate 11 and the electrode film 121 are fixed to each other, and the electrode films 121 and 123. This is because the adhesion with the piezoelectric / electrostrictive film 122 tends to be incomplete. In addition, if the firing temperature of the piezoelectric / electrostrictive film 122 exceeds this range, the piezoelectric / electrostrictive characteristics of the piezoelectric / electrostrictive film 122 tend to deteriorate. Further, the maximum temperature holding time during firing is desirably 1 minute to 10 hours, and more desirably 5 minutes to 4 hours. This is because if the thickness falls below this range, the piezoelectric / electrostrictive film 122 tends to be insufficiently densified. In addition, if it exceeds this range, the piezoelectric / electrostrictive characteristics of the piezoelectric / electrostrictive film 122 tend to deteriorate.

  Note that the heat treatment of the electrode films 121 and 123 is preferably performed together with the baking from the viewpoint of productivity, but this does not prevent the heat treatment from being performed every time the electrode films 121 and 123 are formed. However, when the piezoelectric / electrostrictive film 122 is fired before the heat treatment of the electrode film 123, the electrode film 123 is heat treated at a temperature lower than the firing temperature of the piezoelectric / electrostrictive film 122.

  After the completion of firing, a polarization process and an aging process are performed on the piezoelectric / electrostrictive actuator.

  The piezoelectric / electrostrictive actuator 1 is also manufactured by a green sheet laminating method that is commonly used in the production of multilayer ceramic electronic components. In the green sheet laminating method, a binder, a plasticizer, a dispersant, and a dispersion medium are added to a raw material powder, and ceramics, a binder, a plasticizer, and a dispersion medium are mixed by a ball mill or the like. The obtained slurry is formed into a sheet shape by a doctor blade method or the like to obtain a formed body.

  Subsequently, an electrode paste film is printed on both main surfaces of the molded body by a screen printing method or the like. The electrode paste used here is obtained by adding a solvent, vehicle, glass frit, or the like to the above-described metal or alloy powder.

  Subsequently, the molded body on which the electrode paste film is printed on both main surfaces is bonded to the substrate.

  Thereafter, the substrate on which the laminate is formed is integrally fired, and after the firing is finished, polarization treatment and aging treatment are performed under appropriate conditions.

(Third embodiment)
The third embodiment relates to a multilayer piezoelectric / electrostrictive actuator 2 using the piezoelectric / electrostrictive porcelain composition of the first embodiment.

  FIG. 2 is a schematic diagram of the piezoelectric / electrostrictive actuator 2 of the third embodiment. FIG. 2 is a sectional view of the piezoelectric / electrostrictive actuator 2.

  As shown in FIG. 2, the piezoelectric / electrostrictive actuator 2 has an electrode film 221, a piezoelectric / electrostrictive film 222, an electrode film 223, a piezoelectric / electrostrictive film 224, and an electrode film 225 on the upper surface of the base 21. It has a stacked structure in order. The electrode films 221 and 223 on both main surfaces of the piezoelectric / electrostrictive film 222 face each other with the piezoelectric / electrostrictive film 222 interposed therebetween, and the electrode films 223 and 223 on both main surfaces of the piezoelectric / electrostrictive film 224 are opposed to each other. 225 opposes with the piezoelectric / electrostrictive film 224 interposed therebetween. The laminate 22 in which the electrode film 221, the piezoelectric / electrostrictive film 222, the electrode film 223, the piezoelectric / electrostrictive film 224, and the electrode film 225 are laminated is fixed to the substrate 21. 2 shows a case where the piezoelectric / electrostrictive film has two layers, the piezoelectric / electrostrictive film may have three or more layers.

  As for the plate thickness of the base 21 of the piezoelectric / electrostrictive actuator 2, the central portion 215 to which the laminate 22 is bonded is thinner than the peripheral portion 216. As a result, the bending displacement can be increased while maintaining the mechanical strength of the base 21. The substrate 21 may be used for the piezoelectric / electrostrictive actuator 1 of the second embodiment.

  The piezoelectric / electrostrictive actuator 2 is also manufactured in the same manner as the single-layer piezoelectric / electrostrictive actuator 1 except that the number of piezoelectric / electrostrictive films and electrode films to be formed is increased.

(Fourth embodiment)
The fourth embodiment relates to a multilayer piezoelectric / electrostrictive actuator 3 using the above-described piezoelectric / electrostrictive porcelain composition.

  FIG. 3 is a schematic diagram of the piezoelectric / electrostrictive actuator 3 of the fourth embodiment. FIG. 3 is a cross-sectional view of the piezoelectric / electrostrictive actuator 3.

  As shown in FIG. 3, the piezoelectric / electrostrictive actuator 3 includes a base body 31 in which a unit structure having the same structure as the base body 21 of the third embodiment is repeated. On each of the unit structures of the base 31, a laminate 32 having the same structure as the laminate 22 of the third embodiment is fixed.

  The piezoelectric / electrostrictive actuator 3 is also manufactured in the same manner as the single-layer piezoelectric / electrostrictive actuator 1 except that the number of laminated bodies to be formed and the number of piezoelectric / electrostrictive films and electrode films are increased. .

(Fifth embodiment)
The fifth embodiment relates to a piezoelectric / electrostrictive actuator 4 using the piezoelectric / electrostrictive porcelain composition of the first embodiment.

  4 to 6 are schematic views of the piezoelectric / electrostrictive actuator 4 of the fifth embodiment. 4 is a perspective view of the piezoelectric / electrostrictive actuator 4, FIG. 5 is a longitudinal sectional view of the piezoelectric / electrostrictive actuator 4, and FIG. 6 is a transverse sectional view of the piezoelectric / electrostrictive actuator 4.

  As shown in FIGS. 4 to 6, the piezoelectric / electrostrictive actuator 4 includes the piezoelectric / electrostrictive film 402 and the internal electrode film 404 that are alternately stacked in the direction of the axis A. It has a structure in which external electrode films 416 and 418 are formed on end faces 412 and 414 of a laminate 410 in which an internal electrode film 404 is laminated.

  As shown in the exploded perspective view of FIG. 7 showing a state in which a part of the piezoelectric / electrostrictive actuator 4 is disassembled 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 actuators 1 to 3 already described, the piezoelectric / electrostrictive actuator 4 does not have a base to which the multilayer body 410 is fixed. The piezoelectric / electrostrictive actuator 4 is also referred to as an “offset type piezoelectric / electrostrictive actuator” 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 a sintered body of the piezoelectric / electrostrictive ceramic composition of the first embodiment. The film thickness of the piezoelectric / electrostrictive film 402 is preferably 5 to 500 μm. This is because, if it falls below this range, it will be difficult to produce a green sheet described later. 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 film thickness of the internal electrode film 402 is desirably 10 μm or less. This is because if the thickness exceeds this range, the internal electrode film 402 functions as a relaxation layer and the displacement tends to be small. Further, in order for the internal electrode film 402 to properly fulfill its role, the film thickness is desirably 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. .

  In manufacturing the piezoelectric / electrostrictive actuator 4, a binder, a plasticizer, a dispersant, and a dispersion medium are added to the raw material powder of the piezoelectric / electrostrictive ceramic composition of the first embodiment, and these are mixed by a ball mill or the like. The obtained slurry is formed into a sheet shape by a doctor blade method or the like to obtain a green sheet.

  Subsequently, the green sheet is punched using a punch or die to form alignment holes or the like in the green sheet.

  Subsequently, an electrode paste is applied to the surface of the green sheet by screen printing or the like, and a green sheet on which an electrode paste pattern is formed is obtained. There are two types of electrode paste patterns: a first electrode paste pattern that becomes the first internal electrode film 406 after firing and a second electrode paste pattern that becomes the second internal electrode film 408 after firing. . Of course, the internal electrode films 406 and 408 may be obtained after firing by using only one type of electrode paste pattern and rotating the orientation of the green sheets every other 180 °.

  Next, the green sheet on which the pattern of the first electrode paste is formed and the green sheet on which the pattern of the second electrode paste is formed are alternately stacked, and the green sheet to which no electrode paste is applied is the uppermost part. After further overlapping, the stacked green sheets are pressed and pressure-bonded in the thickness direction. At this time, the positions of the alignment holes formed in the green sheet are aligned. Further, when the stacked green sheets are pressure-bonded, it is also desirable to heat the mold used for pressure bonding so that the green sheets are pressure-bonded while being heated.

  The green sheet pressure-bonded body thus obtained is fired, and the obtained sintered body is processed with a dicing saw or the like to obtain a laminated body 410. Then, the external electrode films 416 and 418 are formed on the end faces 412 and 414 of the laminate 410 by baking, vapor deposition, sputtering, etc., and the piezoelectric / electrostrictive actuator 4 is obtained by performing polarization treatment and aging treatment.

  The above second to fifth embodiments are merely examples, and are not intended to limit the present invention. That is, various modifications other than the above second to fifth embodiments are envisaged within the scope of the present invention.

10. Evaluation Methods Evaluation methods for piezoelectric / electrostrictive characteristics of experimental examples and comparative examples according to the present invention performed in examples described later will be described below.

(1) Piezoelectric constant The piezoelectric constant d ₃₁ (pm / V) is measured by measuring the frequency-impedance characteristics and capacitance of the piezoelectric / electrostrictive element with an impedance analyzer and measuring the dimensions of the piezoelectric / electrostrictive element with a micrometer. Then, it was obtained by calculating from the resonance frequency and antiresonance frequency of the fundamental wave of the longitudinal vibration in the long side direction, the capacitance and the dimensions.

(2) Strain rate The strain rate S ₄₀₀₀ (ppm) when a high electric field is applied is applied to the electrode with an adhesive by applying an electric field induced strain in the long side direction when a voltage of 4 kV / mm is applied to the gold electrodes on both main surfaces. It was obtained by measuring with an attached strain gauge.

(3) Curie temperature Using a Curie point measuring device (manufactured by Tokyo Kogyo Co., Ltd., LCZ meter), the dielectric constant was measured from room temperature to 500 ° C. under conditions of a frequency of 1 kHz and a heating rate of 5 ° C./min. The temperature at which the rate was the highest was taken as the Curie temperature (Tc).

  The present invention will be described in more detail with reference to the following examples, but the technical scope of the present invention is not limited to these examples.

  In this example, a suitable content of Zn derived from the third component for obtaining desired piezoelectric / electrostrictive characteristics in the piezoelectric / electrostrictive sintered body according to the present invention is confirmed and verified.

(Manufacture of piezoelectric / electrostrictive element for evaluation)
In producing a piezoelectric / electrostrictive element for evaluation, first, lithium carbonate (Li ₂ CO ₃ ), sodium hydrogen tartrate monohydrate (C ₄ H ₅ O ₆ Na · H ₂ O), potassium hydrogen tartrate (C ₄₎ H ₅ O ₆ K), niobium oxide (Nb ₂ O ₅ ), tantalum oxide (Ta ₂ O ₅ ), antimony oxide (Sb ₂ O ₃ ), manganese dioxide (MnO ₂ ), (as a source of the selective element) Powders of raw materials such as strontium carbonate (SrCO ₃ ), barium carbonate (BaCO ₃ ), zirconium oxide (ZrO ₂ ), and zinc oxide (ZnO) were weighed so as to have a predetermined composition in the fired oxide.

  Specifically, in this example, for each parameter relating to the composition of the first and second perovskite oxides in the fired oxide (piezoelectric / electrostrictive sintered body), a = 1.010. , X = 0.36, y = 0.07, z = 0.082, w = 0.040, p = 0.50, and t = 0.10, and oxidation after firing In 100 parts by mole of the first perovskite oxide in the first component of the product, the atomic equivalent of Mn is fixed at 0.02 molar part, and the atomic equivalent of Sr is 0.10. Fixed in the mole part. Furthermore, the ratio of the second perovskite oxide to the sum of the first perovskite oxide and the second perovskite oxide in the sintered oxide (piezoelectric / electrostrictive sintered body) is 20 mol%. It became fixed with.

  In addition, about the 3rd component (ZnO in a present Example) which contains the said Zn as a main component, as shown in Table 1, content in the oxide after baking is 0.00 mol% in conversion of Zn atom (comparison). Example 1), 0.01 mol%, 0.10 mol%, 0.50 mol%, 1.00 mol%, and 2.50 mol% (Experimental Examples 1 to 5), and 3.00 mol% (Comparative Example 2) Adjusted.

Subsequently, alcohol as a dispersion medium is added to the powder of the weighed raw materials (excluding MnO ₂ and SrCO ₃ in the first component, and the third component containing Zn as a main component (ZnO in this example)). In addition, it was mixed for 16 hours using a ball mill.

Subsequently, the obtained mixed raw material was dried, calcined at 950 ° C. for 5 hours, and pulverized with a ball mill twice. In this process, SrCO ₃ was added after the first calcination, and MnO ₂ and ZnO were added after the _second calcination. As described above, a powder of a composition for obtaining a piezoelectric / electrostrictive sintered body according to the present invention was obtained. The obtained powder was coarsely pulverized and then passed through a 500 mesh sieve to adjust the particle size.

The raw material powder obtained as described above was 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. And the obtained molded object was accommodated in the alumina container, and it baked at 1150 degreeC for 3 hours, and obtained the sintered compact.

  Subsequently, the 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 treatment was performed at 600 to 900 ° C. Thereafter, gold electrodes were formed on both main surfaces of the rectangular sample by sputtering. And these samples were immersed in 70-100 degreeC silicon oil, the voltage of 5 kV / mm was applied to the gold electrode of both main surfaces for 15 minutes, and the polarization process was performed in the thickness direction.

(Piezoelectric / electrostrictive properties)
Using the piezoelectric / electrostrictive element for evaluation prepared as described above, the piezoelectric constant d ₃₁ (pm / V) and the strain rate S ₄₀₀₀ (ppm) when a high electric field was applied were measured. The measurement results are shown in Table 1 below.

As shown in Table 1, in Comparative Example 1 in which no Zn was added, the distortion rate (S ₄₀₀₀ ) when a high electric field was applied was insufficient. On the other hand, in Experimental Examples 1 to 5 in which the Zn addition amount is 0.01 to 2.50 mol%, the piezoelectric constant (d ₃₁ ) and the distortion rate (S ₄₀₀₀ ) when a high electric field is applied are improved. In particular, the improvement rate of the distortion rate (S ₄₀₀₀ ) when a high electric field is applied when the comparative example 1 is used as a target standard is remarkable. However, in Comparative Example 2 in which the Zn addition amount is 3.00 mol%, the piezoelectric constant (d ₃₁ ) and the strain rate (S) when a high electric field is applied are compared with Comparative Example 1 in which no Zn is added. ₄₀₀₀ ) were significantly reduced. This is considered to be due to the occurrence of a heterogeneous phase derived from Zn in the oxide after firing. In addition, about Curie temperature, practical temperature (specifically, 200 degreeC or more) was achieved in both the experiment example and comparative example concerning a present Example.

  From the above results, the suitable content of Zn derived from the third component for obtaining desired piezoelectric / electrostrictive characteristics in the piezoelectric / electrostrictive crystal according to the present invention is 0.01 to 2.50 mol%. It is concluded that

  In this example, the first perovskite oxide and the second perovskite oxide are suitable for obtaining desired piezoelectric / electrostrictive characteristics in the piezoelectric / electrostrictive sintered body according to the present invention. Check and verify the correct ratio.

(Manufacture of piezoelectric / electrostrictive element for evaluation)
In the sintered oxide (piezoelectric / electrostrictive sintered body), the content of the third component (ZnO in this example) containing Zn as a main component is fixed at 0.50 mol% in terms of Zn atoms, and The ratio (α) of the second perovskite oxide to the total sum of the first perovskite oxide and the second perovskite oxide is 0.0 (Comparative Example 3), 0.1, 0 .3, 0.5, and 0.75 (Experimental Examples 6 to 9) and 0.8 (Comparative Example 4). An evaluation piezoelectric / electrostrictive element used in the examples was prepared.

(Piezoelectric / electrostrictive properties)
Using the piezoelectric / electrostrictive element for evaluation prepared as described above, the piezoelectric constant d ₃₁ (pm / V) and the strain rate S ₄₀₀₀ (ppm) when a high electric field was applied were measured. The measurement results are shown in Table 2 below.

As shown in Table 2, in Comparative Example 3 in which the second perovskite oxide (rhombohedral crystal) is not contained in the sintered body, the piezoelectric constant (d ₃₁ ) is remarkably small. In addition, despite the addition of a suitable amount of Zn (confirmed in Example 1 above), the effect of improving the distortion rate (S ₄₀₀₀ ) when a high electric field is applied is insufficient. On the other hand, the ratio (α) of the second perovskite oxide to the total sum of the first perovskite oxide and the second perovskite oxide is 0.1 mol% or more and less than 0.8 mol%. In Experimental Examples 6 to 9 in the range, the strain rate (S ₄₀₀₀ ) when a high electric field was applied was further improved while achieving a piezoelectric constant (d ₃₁ ) of a desired level or higher. However, in Comparative Example 4 in which the ratio α is 0.8, a phenomenon such as insufficient density of the sintered body occurs, and the composition corresponding to these Comparative Examples is fired to obtain a desired sintered material. No body could be obtained and the piezoelectric / electrostrictive properties of these compositions could not be evaluated. Furthermore, in Comparative Example 4, a practical Curie temperature (specifically, 200 ° C. or higher) could not be achieved.

  From the above results, the first perovskite type oxide and the second perovskite type oxide with respect to the sum total of the first perovskite type oxide to obtain desired piezoelectric / electrostrictive characteristics in the piezoelectric / electrostrictive crystal according to the present invention. The ratio (α) of the perovskite oxide 2 is determined to be in the range of 0.1 mol% or more and less than 0.8 mol%.

  As described above, a piezoelectric / electrostrictive obtained by blending a tetragonal component having a specific composition, a rhombohedral component having a specific composition, and zinc oxide so that the composition after firing satisfies a specific condition The piezoelectric / electrostrictive sintered body according to the present invention, which is obtained by preparing a porcelain composition and firing it, is a non-leaded piezoelectric / electrostrictive sintered body, but has a low firing temperature, While having a high electric field and high strain rate and a high Curie temperature (Tc), it is possible to achieve piezoelectric properties that surpass PZT-based piezoelectric / electrostrictive sintered bodies.

  In addition, said description is an illustration in all the phases, Comprising: This invention is not limited to it. It is understood that countless variations that are not illustrated can be envisaged without departing from the scope of the present invention.

  As described above, according to the present invention, a lead-free piezoelectric / electrostrictive firing exhibiting a high electric field induced strain rate not only when a low electric field is applied but also when a high electric field is applied while maintaining a practical Curie temperature. There are provided a bonded body and a piezoelectric / electrostrictive element comprising the piezoelectric / electrostrictive sintered body.

Claims (5)

The first perovskite oxide represented by the general formula (1) {Li _y (Na _1−x K _x ) _1−y } _a (Nb _1−z−w Ta _z Sb _w ) O ₃ , Ba, Sr A first component comprising a compound of one or more selective elements selected from the group consisting of Ca, La, Ce, Nd, Sm, Dy, Ho and Yb, and a compound of Mn,
A second component that is a second perovskite oxide represented by the general formula (2) {Ba _t (K _p Na _1-p ) _1-t } (Zr _t Nb _1-t ) O ₃ , and Zn A third component as a main component,
A piezoelectric / electrostrictive sintered body obtained by firing a composition comprising
In the piezoelectric / electrostrictive sintered body, the content of the third component is in a range that does not cause a Zn-derived heterogeneous phase in the piezoelectric / electrostrictive sintered body, and in the composition of the piezoelectric / electrostrictive sintered body ,
In the general formula (1), a, x, y, z and w are 1 <a ≦ 1.1, 0.30 ≦ x ≦ 0.70, 0.02 ≦ y ≦ 0.10, 0, respectively. ≦ z ≦ 0.5 and 0.01 ≦ w ≦ 0.1 are satisfied,
In the general formula (2), p and t satisfy 0 ≦ p ≦ 1 and 0 <t ≦ 0.5, respectively.
Piezoelectric / electrostrictive sintered body.   2. The piezoelectric / electrostrictive sintered body according to claim 1, wherein the first perovskite oxide and the second perovskite oxide in the piezoelectric / electrostrictive sintered body after firing are combined with each other. A piezoelectric / electrostrictive sintered body in which the ratio of the second perovskite oxide is 10 mol% or more and less than 80 mol%.   The piezoelectric / electrostrictive sintered body according to claim 1 or 2, wherein the content of the third component in the piezoelectric / electrostrictive sintered body after firing is 0.01 mol% or more in terms of Zn atoms. The piezoelectric / electrostrictive sintered body is less than 3.00 mol%.   The piezoelectric / electrostrictive sintered body according to any one of claims 1 to 3, wherein the first perovskite oxide in the first component in the piezoelectric / electrostrictive sintered body after firing. The piezoelectric / electrostrictive sintered body, wherein a content of the Mn compound with respect to 100 mol parts in terms of Mn atoms is 5 mol parts or less.   A piezoelectric / electrostrictive element comprising the piezoelectric / electrostrictive sintered body according to any one of claims 1 to 4, and at least a pair of electrodes.

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