JP5129067B2 - Piezoelectric / electrostrictive porcelain composition and piezoelectric / electrostrictive element - Google Patents

Description

  The present invention relates to a piezoelectric / electrostrictive porcelain composition and a piezoelectric / electrostrictive element using the piezoelectric / electrostrictive porcelain composition.

  Piezoelectric / electrostrictive actuators have the advantage that displacement can be precisely controlled on the order of submicrons. In particular, a piezoelectric / electrostrictive actuator using a sintered body of a piezoelectric / electrostrictive porcelain composition as a piezoelectric / electrostrictive body can precisely control displacement, and has high electromechanical conversion efficiency. It has the advantages of high power, fast response speed, high durability, and low power consumption. Taking advantage of these advantages, it is employed in inkjet printer heads, diesel engine injectors, and the like.

As a piezoelectric / electrostrictive porcelain composition for a piezoelectric / electrostrictive actuator, a Pb (Zr, Ti) O ₃ (PZT) -based piezoelectric / electrostrictive porcelain composition has been conventionally used. (Li, Na, K) (Nb, Ta) O ₃ -based piezoelectric / electrostrictive porcelain compositions have been studied since the elution of lead on the global environment is strongly concerned. .

Further, as shown in Patent Document 1 and Patent Document 2, a (Li, Na, K) (Nb, Ta, Sb) O ₃ type piezoelectric material containing Sb as a B site element in order to improve piezoelectric / electrostrictive characteristics. / Electrostrictive porcelain compositions are also being studied.

Further, in Patent Document 3, in the (Li, Na, K) (Nb, Ta, Sb) O ₃ -based piezoelectric / electrostrictive porcelain composition, the number of atoms of the A site element is set to be larger than the number of atoms of the B site element. It has been shown that the piezoelectric / electrostrictive characteristics can be improved by making it excessive.

JP 2003-206179 A JP 2004-244299 A International Publication No. 2006/095716

However, the conventional (Li, Na, K) (Nb, Ta, Sb) O ₃ based piezoelectric / electrostrictive porcelain composition does not necessarily have an electric field induced strain when a high electric field is applied, which is important for a piezoelectric / electrostrictive actuator. There was a problem that it was not enough.

The present invention has been made to solve this problem, and (Li, Na, K) (Nb, Ta, Sb) O ₃ type piezoelectric / electrostrictive porcelain having good electric field induced strain when a high electric field is applied. An object is to provide a composition.

The invention of claim 1 is represented by the general formula {Li _y (Na _1−x K _x ) _1−y } _a (Nb _1−z−w Ta _z Sb _w ) O ₃ , and a, x, y, z And w are 1 <a ≦ 1.05, 0.30 ≦ x ≦ 0.70, 0.02 ≦ y ≦ 0.10, 0 ≦ z ≦ 0.5 and 0.01 ≦ w ≦ 0. 1 is a piezoelectric / electrostrictive porcelain composition comprising a perovskite oxide having a composition satisfying 1 and a Mn compound added to the perovskite oxide. Mn is not taken into the crystal lattice of the perovskite oxide. The amount of the Mn compound added to 100 mol parts of the perovskite oxide is 0.001 mol part or more and 0.1 mol part or less in terms of Mn atoms.

The invention of claim 2 is represented by the general formula _{{Li y (Na 1-x} K x) 1-y} a (Nb 1-z-w Ta z Sb w) O 3, a, x, y, z And w are 1 <a ≦ 1.05, 0.30 ≦ x ≦ 0.70, 0.02 ≦ y ≦ 0.10, 0 ≦ z ≦ 0.5 and 0.01 ≦ w ≦ 0. 1 in an X-ray diffraction pattern using a perovskite oxide having a composition satisfying 1 and a Mn compound added to the perovskite oxide, and using Cu—Kα as an X-ray source. Of the two main peaks derived from the perovskite compound found in the range, the ratio of the face spacing determined from the low angle peak to the face spacing determined from the high angle peak is from 1.003 to 1.025 It is a piezoelectric / electrostrictive porcelain composition. Mn is not taken into the crystal lattice of the perovskite oxide. The amount of the Mn compound added to 100 mol parts of the perovskite oxide is 0.001 mol part or more and 0.1 mol part or less in terms of Mn atoms.

The invention of claim 3 is the piezoelectric / electrostrictive porcelain composition according to claim 1 or 2 which does not contain a heterogeneous phase of LiSbO ₃ .

According to a fourth aspect of the present invention, there is provided a piezoelectric / electrostrictive film that is a sintered body of the piezoelectric / electrostrictive porcelain composition according to any one of the first to third aspects, and the piezoelectric / electrostrictive film. A piezoelectric / electrostrictive element including an electrode film on a main surface.

The invention of claim 5, wherein the piezoelectric / electrostrictive film is a piezoelectric / electrostrictive element according to claim 4 containing no hetero-phase of LiSbO _3.

According to the present invention, it is possible to provide a (Li, Na, K) (Nb, Ta, Sb) O ₃ based piezoelectric / electrostrictive porcelain composition having a good electric field induced strain when a high electric field is applied.

  Hereinafter, a piezoelectric / electrostrictive ceramic composition according to a preferred embodiment of the present invention will be described, and then an actuator using the piezoelectric / electrostrictive ceramic composition will be described. However, the following description does not mean that the application of the piezoelectric / electrostrictive porcelain composition of the present invention is limited to an actuator. For example, the piezoelectric / electrostrictive ceramic composition of the present invention may be used for a piezoelectric / electrostrictive element such as a sensor.

<1 Piezoelectric / electrostrictive porcelain composition>
{composition}
A piezoelectric / electrostrictive porcelain composition according to a preferred embodiment of the present invention includes lithium (Li), sodium (Na), and potassium (K) as A site elements, and niobium (Nb) and antimony (Sb) as B site elements. ), And a perovskite oxide in which the ratio of the total number of atoms of the A site element to the total number of atoms of the B site element (so-called A / B ratio) is greater than 1, a trace amount of Mn compound is added. The perovskite oxide may further contain a monovalent element such as silver (Ag) as the A site element, or a pentavalent element such as tantalum (Ta) or vanadium (V) as the B site element. Further, it may be contained.

The composition of the perovskite oxide as the main component is represented by the general formula {Li _y (Na _1−x K _x ) _1−y } _a (Nb _1−zw Ta _z Sb _w ) O ₃ , a, x, y, z and w are 1 <a ≦ 1.05, 0.30 ≦ x ≦ 0.70, 0.02 ≦ y ≦ 0.10, 0 ≦ z ≦ 0.5 and 0.01 ≦ w, respectively. It is preferable to satisfy ≦ 0.1.

  The reason why the A / B ratio is 1 <a is to promote grain growth and densify. Those having an A / B ratio of 1 ≧ a require heating at 1100 ° C. or higher in order to promote grain growth. In this case, evaporation of the alkali component is likely to occur, and the characteristics become unstable due to fluctuations in the composition. By setting the A / B ratio to 1 <a, the firing temperature can be set to 1100 ° C. or less, and the variation of the composition can be avoided. This is presumed to be due to the presence of a surplus alkali component that affects the generation of a different phase (low melting point phase) during the firing process.

  On the other hand, the reason why the A / B ratio is set to a ≦ 1.05 is that if it exceeds this range, the dielectric loss increases and the electric field induced strain at the time of applying a high electric field tends to decrease. The increase in dielectric loss is a serious problem in a piezoelectric / electrostrictive ceramic composition for an actuator that applies a high electric field.

The reason why the Sb substitution amount is set to 0.01 ≦ w ≦ 0.1 is that a tetragonal-orthorhombic phase transition temperature (hereinafter simply referred to as “phase transition temperature”) in which the piezoelectric / electrostrictive characteristics become high within this range. This is because the electric field induced strain when a high electric field is applied can be increased without greatly changing _TOT (preferably 50 ° C. or less). In particular, when the Sb substitution amount is set to 0.01 ≦ w ≦ 0.05, the electric field induced strain at the time of applying a high electric field is particularly increased without substantially changing the phase transition temperature _TOT (desirably 10 ° C. or less). be able to. This is because, when the A / B ratio is 1 <a, when the Sb substitution amount exceeds the range of 0.01 ≦ w ≦ 0.05, a LiSbO ₃ heterogeneous phase is generated inside the sintered body, and the perovskite unit This is because the phase cannot be obtained and the phase transition temperature _TOT tends to increase.

  The K, Li, and Ta amounts were set to 0.30 ≦ x ≦ 0.70, 0.02 ≦ y ≦ 0.10, and 0 ≦ z ≦ 0.5, respectively. This is because an electrostrictive porcelain composition can be obtained.

  For example, when x is less than this range, the piezoelectric / electrostrictive characteristics are rapidly lowered. On the other hand, if x exceeds this range, sintering becomes difficult and the firing temperature must be increased. It is not desirable to increase the firing temperature because the alkali component contained in the piezoelectric / electrostrictive porcelain composition evaporates and the piezoelectric / electrostrictive characteristics cannot be obtained stably when the firing temperature is increased. is there.

  If y is less than this range, sintering is still difficult, and the firing temperature must be increased. On the other hand, when y exceeds this range, precipitation of heterogeneous phases increases, and the insulation properties decrease.

  Furthermore, if z exceeds this range, sintering is still difficult, and the firing temperature must be increased.

  It is desirable to add the Mn compound, which is a subcomponent, so that the amount of Mn atom conversion relative to 100 mol parts of the perovskite oxide is 3 mol parts or less. The reason why the amount of Mn compound added is 3 mol parts or less is that if it exceeds this range, the dielectric loss increases, and the electric field induced strain when a high electric field is applied tends to decrease.

  Here, 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 added to 100 mole parts of perovskite oxide, the sintered body can be easily polarized, and synergistic with substitution by Sb. Due to the effect, the electric field induced strain when a high electric field is applied can also be increased.

The Mn compound is desirably a compound of Mn whose valence is mainly divalent. For example, manganese oxide (MnO) or another compound in which manganese is dissolved is desirable, and a compound in which manganese is dissolved in trilithium niobate (Li ₃ NbO ₄ ) is particularly desirable. Here, “mainly divalent” may include a compound of Mn whose valence is other than divalent, and it means that the most contained valence may be divalent. The valence of Mn can be confirmed by an X-ray absorption near-edge structure (XANES). Further, it is desirable that Mn is present in the ceramic sintered body as an element constituting a heterogeneous phase of the manganese compound without being taken into the crystal lattice of the perovskite oxide that is the parent phase.

By introducing such a Mn compound into the sintered body, hardening due to the addition of the Mn compound can be prevented, and the electric field induced strain can be increased.

{Phase transition temperature}
Generally speaking, (Li, Na, K) (Nb, Ta, Sb) O ₃ -based perovskite oxides and modified products thereof are cubic, tetragonal, or orthorhombic from high temperature to low temperature. In the piezoelectric / electrostrictive ceramic composition according to the preferred embodiment of the present invention, it is desirable to select the composition so that the phase transition temperature T _OT is in the vicinity of room temperature. It is further desirable to select the composition so that This is because if the phase transition temperature _TOT is in the vicinity of room temperature, the electric field induced strain at the time of applying a high electric field can be increased. Here, the phase transition temperature is a temperature at which the dielectric constant has an extreme value with respect to the temperature. (The first peak when the temperature is lowered from a high temperature is the cubic-tetragonal phase transition temperature, and the second peak is the tetragonal-orthorhombic phase transition temperature. peak at different slightly here, tetragonal during heating -. the orthorhombic phase transition temperature T _OT)..

{Crystal system and lattice strain}
Moreover, in the piezoelectric / electrostrictive porcelain composition according to a preferred embodiment of the present invention, it is desirable to select a composition so that the crystal system is tetragonal or orthorhombic and the lattice strain is reduced to some extent. Specifically, in the X-ray diffraction pattern using Cu-Kα ray as the X-ray source, among the two main peaks derived from the perovskite compound having a large intensity found in the range of 2θ = 44 to 47 °, It is desirable to select the composition so that the ratio of the interplanar spacing obtained from the low angle peak to the interplanar spacing obtained from the high angle peak is 1.003 or more and 1.025 or less. Here, when the crystal system is a tetragonal system, the plane spacing obtained from the high-angle peak corresponds to the (200) plane spacing, and the plane spacing obtained from the low-angle peak corresponds to the (002) plane spacing. The ratio means the ratio c / a of the lattice constant c in the c-axis direction to the lattice constant a in the a-axis direction. That is, when the crystal system is tetragonal, it is desirable to select the composition so that c / a is 1.003 or more and 1.025 or less. This is because if the interplanar spacing is within these ranges, the domain can be easily rotated, and the electric field induced strain when a high electric field is applied can be improved.

{Manufacture of raw material powder}
In the production of the raw material powder of the piezoelectric / electrostrictive porcelain composition, first, a dispersion medium is added to the raw material of the constituent elements (Li, Na, K, Nb, Ta, Sb, Mn, etc.) of the piezoelectric / electrostrictive porcelain composition. Add and mix with a ball mill. Compounds such as oxides, carbonates and tartrates can be used as the raw material, and organic solvents such as ethanol, toluene and acetone can be used as the dispersion medium. Then, the dispersion medium is removed from the obtained mixed slurry by a technique such as evaporation drying or filtration to obtain a mixed raw material. Subsequently, the raw material powder can be obtained by calcining the mixed raw material at 600 to 1300 ° C. In addition, in order to obtain the raw material powder of a desired particle diameter, you may grind | pulverize with a ball mill etc. after calcination. Further, the raw material powder may be produced by an alkoxide method or a coprecipitation method instead of the solid phase reaction method. Further, a raw material of Mn for supplying Mn constituting the Mn compound may be added after the perovskite oxide is synthesized. In this case, it is desirable to add to the perovskite oxide synthesized with manganese dioxide (MnO ₂ ) as a raw material for Mn. The tetravalent Mn constituting the manganese dioxide added in this way is reduced during firing to divalent Mn, contributing to the improvement of the electric field induced strain. Alternatively, a perovskite oxide may be synthesized through a B-site element columbite compound.

  The average particle diameter of the raw material powder is preferably 0.07 to 10 μm, and more preferably 0.1 to 3 μm. Moreover, you may heat-process raw material powder at 400-850 degreeC in order to adjust the particle diameter of raw material powder. Finer particles are easier to be integrated with other particles. Therefore, when this heat treatment is performed, a raw material powder having a uniform particle size can be obtained, and a sintered body having a uniform particle size can be obtained.

<2 Piezoelectric / electrostrictive actuator>
{Overall structure}
1 and 2 are schematic views of structural examples of the piezoelectric / electrostrictive actuators 1 and 2 using the above-described piezoelectric / electrostrictive porcelain composition, and FIG. 1 shows a single-layer piezoelectric / electrostrictive actuator 1. FIG. 2 is a sectional view of the multilayer piezoelectric / electrostrictive actuator 2.

  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 stacked 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 are opposed to 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.

  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 substrate 21. Are stacked in this order. The electrode films 221 and 223 on both main surfaces of the piezoelectric / electrostrictive film 222 are opposed to each other with the piezoelectric / electrostrictive film 222 interposed therebetween, and the electrode films on both main surfaces of the piezoelectric / electrostrictive film 224 are disposed. 223 and 225 are opposed to each other 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.

  Here, “adhesion” means that the laminates 12 and 22 are bonded to the substrates 11 and 21 by a solid-phase reaction at the interface between the substrates 11 and 21 and the laminates 12 and 22 without using an organic adhesive or an inorganic adhesive. It means joining. 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 actuators 1 and 2, when a voltage is applied, the piezoelectric / electrostrictive bodies 122, 222, and 224 expand and contract in a direction perpendicular to the electric field according to the applied voltage, and as a result, bending displacement is caused. Arise.

{Piezoelectric / electrostrictive film}
The piezoelectric / electrostrictive films 122, 222, and 224 are sintered bodies of the above-described piezoelectric / electrostrictive ceramic composition.

  The film thickness of the piezoelectric / electrostrictive films 122, 222, and 224 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 it falls below this range, densification tends to be insufficient. Further, if it exceeds this range, the shrinkage stress at the time of sintering increases, so that it is necessary to increase the thickness of the substrates 11 and 21, and it becomes difficult to miniaturize the piezoelectric / electrostrictive actuators 1 and 2. is there.

{Electrode film}
The material of the electrode films 121, 123, 221, 223, and 225 is a metal such as platinum, palladium, rhodium, gold, 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. Also, depending on the firing temperature, an alloy such as silver-palladium can be suitably used.

  The film thicknesses of the electrode films 121, 123, 221, 223, and 225 are preferably 15 μm or less, and more preferably 5 μm or less. This is because exceeding this range, the electrode films 121, 123, 221, 223, and 225 function as relaxation layers, and the flexural displacement tends to decrease. Moreover, in order for the electrode films 121, 123, 221, 223, and 225 to appropriately fulfill their roles, the film thickness is preferably 0.05 μm or more.

  The electrode films 121, 123, 221, 223, and 225 are preferably formed so as to cover regions that substantially contribute to the bending displacement of the piezoelectric / electrostrictive films 122, 222, and 224. For example, it is preferable that the piezoelectric / electrostrictive films 122, 222, and 224 are formed so as to cover regions of 80% or more of both main surfaces of the piezoelectric / electrostrictive films 122, 222, and 224, including the central portion.

{Substrate}
Although the material of the base | substrates 11 and 21 is ceramics, there is no restriction | limiting in the kind. However, from the viewpoint of heat resistance, chemical stability, and insulation, 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. Is preferred. Among these, stabilized zirconium oxide is more preferable from the viewpoint of mechanical strength and toughness. Here, “stabilized zirconium oxide” refers to zirconium oxide in which the phase transition of the crystal is suppressed by addition of a stabilizer, and includes partially stabilized zirconium oxide in addition to stabilized zirconium oxide.

  Examples of 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. it can. Of these, zirconium oxide containing yttrium oxide as a stabilizer is preferred because of its particularly high mechanical strength. The content of yttrium oxide is preferably 1.5 to 6 mol%, and more preferably 2 to 4 mol%. In addition to yttrium oxide, it is more preferable 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 substrates 11 and 21 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 actuators 1 and 2 tends to be lower than this range. Further, if the range is exceeded, the rigidity of the substrates 11 and 21 is increased, and the bending displacement due to expansion / contraction of the piezoelectric / electrostrictive films 122, 222, and 224 when a voltage is applied tends to decrease.

  The surface shape of the substrates 11 and 21 (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. Rounding may be performed. It is good also as a compound form which combined these basic forms.

  The plate thickness of the substrate 11 of the single-layer piezoelectric / electrostrictive actuator 1 is uniform. In contrast, the thickness of the base 21 of the multilayer piezoelectric / electrostrictive actuator 2 is such that the central portion 215 to which the laminate 22 is bonded is thinner than the peripheral portion 216. This is to increase the bending displacement while maintaining the mechanical strength of the base 21. The substrate 21 may be used for the single-layer piezoelectric / electrostrictive actuator 1.

  As shown in the sectional view of FIG. 3, the base body 21 shown in FIG. 2 may be used as a unit structure, and a base body 31 in which the unit structure is repeated may be used. In this case, the piezoelectric / electrostrictive actuator 3 is configured by fixing the laminated body 32 on each of the unit structures.

{Manufacture of piezoelectric / electrostrictive actuators}
In manufacturing the single-layer piezoelectric / electrostrictive actuator 1, first, 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. Can do. Among these, from the viewpoint of bonding properties with the substrate 11 and the piezoelectric / electrostrictive film 122, a sputtering method or a screen printing method is preferable. The formed electrode film 121 can be 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, or the like. It can form by the method of. Among them, the screen printing method is preferable in that the accuracy of the planar shape and the film thickness is high and the piezoelectric / electrostrictive film can be continuously formed.

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

  Thereafter, the substrate 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 preferably 800 to 1250 ° C, and more preferably 900 to 1200 ° C. Below this range, densification of the piezoelectric / electrostrictive film 122 becomes insufficient, and adhesion between the substrate 11 and the electrode film 121 and adhesion between the electrode films 121 and 123 and the piezoelectric / electrostrictive film 122 are not achieved. This is because they tend to be perfect. In addition, if it exceeds this range, the piezoelectric / electrostrictive characteristics of the piezoelectric / electrostrictive film 122 tend to deteriorate. The maximum temperature holding time during firing is preferably 1 minute to 10 hours, and more preferably 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 firing 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 firing is complete, polarization treatment is performed under appropriate conditions. The polarization treatment can be performed by a well-known method, and although it depends on the Curie temperature of the piezoelectric / electrostrictive film 122, it is preferably performed by heating to 40 to 200 ° C.

  The multilayer piezoelectric / electrostrictive actuator 2 is 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. Can do.

  The piezoelectric / electrostrictive actuator 1 can also be 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, first, a binder, a plasticizer, a dispersant and a dispersion medium are added to the raw material powder and mixed by a ball mill or the like. And the obtained slurry is shape | molded by the doctor blade method etc. in a sheet shape, and a molded object is obtained.

  Subsequently, a film of electrode paste 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 is performed under appropriate conditions.

<3 Another example of piezoelectric / electrostrictive actuator>
4 to 6 are schematic views of structural examples of the piezoelectric / electrostrictive actuator 4 using the piezoelectric / electrostrictive porcelain composition described above. FIG. 4 is a perspective view of the piezoelectric / electrostrictive actuator 4, FIG. FIG. 6 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 films 406 and the second internal electrode films 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 above-described piezoelectric / electrostrictive ceramic composition. 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, depending on the firing temperature, an alloy such as silver-palladium can also be suitably used.

  The film thickness of the internal electrode film 402 is preferably 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. In order for the internal electrode film 402 to properly fulfill its role, the film thickness is preferably 0.1 μm or more.

  4 to 6 show 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, first, a binder, a plasticizer, a dispersant, and a dispersion medium are added to the raw material powder of the above-described piezoelectric / electrostrictive porcelain composition and mixed by a ball mill or the like. Then, 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 to obtain a green sheet on which an electrode paste pattern is formed. 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 on which the electrode paste is not applied is placed on the top. After further overlapping, the stacked green sheets are pressed in the thickness direction and pressure bonded. 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 laminate 410 can be obtained by firing the pressure-bonded green sheet thus obtained and processing the obtained sintered body with a dicing saw or the like. The piezoelectric / electrostrictive actuator 4 can be obtained by forming the external electrode films 416 and 418 on the end faces 412 and 414 of the laminated body 410 by baking, vapor deposition, sputtering, or the like and performing polarization treatment.

  Hereinafter, Examples 1 to 8 relating to the piezoelectric / electrostrictive ceramic composition of the present invention and Comparative Examples 1 to 8 relating to the piezoelectric / electrostrictive ceramic composition outside the scope of the present invention will be described. However, the examples described below do not limit the scope of the present invention.

{Manufacture of piezoelectric / electrostrictive element for evaluation}
In producing a piezoelectric / electrostrictive element for evaluation, first, lithium carbonate (Li ₂ CO ₃ ), sodium tartrate monohydrate (C ₄ H ₅ O ₆ Na.H ₂ O), potassium tartrate (C ₄ H) _The raw materials such as ₅ O ₆ K), niobium oxide (Nb ₂ O ₅ ), tantalum oxide (Ta ₂ O ₅ ), and antimony oxide (Sb ₂ O ₃ ) are made to have the compositions shown in Tables 1 to 3. Weighed. X, y, z, w and a in the list of Tables 1 to 3 are represented by the general formula {Li _y (Na _1−x K _x ) _1−y } _a (Nb _1−zw Ta _z Sb _w ) O ₃ , the amount of Mn is the amount added relative to 100 mole parts of the perovskite oxide represented by the general formula.

Subsequently, alcohol was added to the raw material as a dispersion medium and mixed for 16 hours by a ball mill. Subsequently, the obtained mixed raw material was dried, calcined at 800 ° C. for 5 hours, and pulverized with a ball mill twice to obtain a raw material powder of a piezoelectric / electrostrictive ceramic composition. Note that the raw material powder, for Examples 1 to 21 and Comparative Example 1, was added MnO ₂ so that the amount shown in Table 1 and Table 3.

  Next, the raw material powder was coarsely pulverized and then passed through a 500 mesh sieve to adjust the particle size.

The raw material powder thus obtained was compacted into a disc shape having a diameter of 18 mm and a plate thickness of 5 mm at a pressure of 2.0 × 10 ⁸ Pa. And the compacting body was accommodated in the alumina container, and it baked at 950-1050 degreeC for 3 hours, and obtained the sintered compact (piezoelectric / electrostrictive body).

  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 by sputtering on both main surfaces of the rectangular sample. This was immersed in silicon oil at room temperature, and a voltage of 5 kV / mm was applied to the gold electrodes on both main surfaces for 15 minutes to perform polarization treatment in the thickness direction.

{Electrical and temperature characteristics}
Using the piezoelectric / electrostrictive elements for evaluation of Examples 1 to 8 and Comparative Examples 1 to 8 fired at 1000 ° C., near the piezoelectric constant d ₃₁ (pm / V), room temperature, and phase transition temperature T _OT The distortion rate S ₄₀₀₀ (ppm) was measured. The measurement results are shown in Tables 1 to 3. The piezoelectric constant d ₃₁ is a fundamental wave of the longitudinal vibration of the long side direction 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. It was obtained by calculating from the resonance frequency and antiresonance frequency, capacitance, and dimensions. Strain ratio S ₄₀₀₀ was obtained by measuring a strain gauge affixed to the electrode with an adhesive electric-field-induced strain in the long side direction at the time of applying a voltage of 4 kV / mm to the gold electrode on both main surfaces. A method for measuring the phase transition temperature _TOT will be described later.

  The piezoelectric / electrostrictive porcelain composition described above can be satisfactorily sintered at least in the range of 950 to 1050 ° C., and the piezoelectric / electrostrictive element of the piezoelectric / electrostrictive element fired at 970 ° C. and 1030 ° C. Since the tendency of the strain characteristics was the same as that of the piezoelectric / electrostrictive element fired at 1000 ° C., Tables 1 to 3 show the piezoelectric / electrostrictive elements of the piezoelectric / electrostrictive element fired at 1000 ° C. Only the distortion characteristics are shown.

With reference to Tables 1 and 2, as is clear when Examples 1 to 3 and 5 to 6 are compared with Comparative Examples 2 to 7, the Sb substitution amount is in the range of 0.01 ≦ w ≦ 0.10. In the formula, {Li _0.06 (Na _0.55 K _0.45 ) _0.94 } _1.01 (Nb _0.918-w Ta _0.082 Sb _w ) O ₃ is represented by 0.02 mole part (in terms of Mn atom) per 100 mole parts of perovskite oxide. The strain ratio S ₄₀₀₀ can be remarkably improved by adding 0.02 mol part of Mn compound. As is clear from Examples 3 and 8 and Comparative Example 4, the amount of Sb substitution represented by the chemical formula {Li _0.06 (Na _0.55 K _0.45 ) _0.94 } _1.01 (Nb _0.878 Ta _0.082 Sb _0.04 ) O ₃ is w = The amount of Mn compound added to 100 mol parts of 0.04 perovskite oxide is 0,0.02,0.1 mol parts (respectively, 0.02,0.1 mol parts in terms of Mn atoms) By increasing in this order, the distortion rate S ₄₀₀₀ can be improved.

However, as is clear from comparison between Comparative Example 1 and Comparative Example 8, the amount of Sb substitution represented by the chemical formula {Li _0.06 (Na _0.55 K _0.45 ) _0.94 } _1.01 (Nb _0.798 Ta _0.082 Sb _0.12 ) O ₃ is Even if 0.02 mole part (0.02 mole part in terms of Mn atom) of Mn compound is added to 100 mole part of perovskite oxide having w = 0.12, the strain rate _S4000 cannot be improved.

Furthermore, the amount of Li substitution was decreased (y = 0.06 → 0.05) and the amount of Ta substitution was increased (z = 0.082 → 0.160) compared to Examples 1 to 3 and Examples 9 to 12, the Li substitution amount was increased (y = 0.06 → 0.07) and the Ta substitution amount was decreased (z = 0.082 → 0) compared with Examples 1 to 3 and Examples 13 to 16. The A / B ratio was increased / decreased from Example 3 (a = 1.01 → 1.005 to 1.03), and the K amount was increased / decreased from Examples 17 to 19 and Example 3 (x = 0.45 → 0.3 to 0.7) Also in Examples 13 and 14, a good distortion _S4000 could be obtained except for Example 19 in which some kind of heterogeneous phase was considered to be generated.

In addition, as is apparent from Examples 1 to 7, it is possible to obtain a particularly good strain rate S ₄₀₀₀ near room temperature when the Sb substitution amount is in the range of 0.01 ≦ w ≦ 0.05.

8, Sb substitution amount for Examples 2 to 6 w = 0.02,0.04,0.05,0.06,0.08, a diagram showing the temperature change of the strain ratio S _4000.

As shown in FIG. 8, 0.02 mol part per 100 mol part of the perovskite oxide represented by the general formula {Li _0.06 (Na _0.55 K _0.45 ) _0.94 } _1.01 (Nb _0.918-w Ta _0.082 Sb _w ) O ₃ When the amount of Sb substitution is in the range of w ≦ 0.5 when the amount of MnO ₂ is added, the temperature at which the strain rate S ₄₀₀₀ becomes maximum is hardly changed even when the amount of Sb substitution increases. When the Sb substitution amount exceeds the range, the Sb substitution amount increases and the temperature at which the strain rate _S4000 becomes maximum increases. Therefore, 0.02 mol part of Mn compound is added to 100 mol part of the perovskite oxide represented by the general formula {Li _0.06 (Na _0.55 K _0.45 ) _0.94 } _1.01 (Nb _0.918-w Ta _0.082 Sb _w ) O _3. When added, if the Sb substitution amount is in the range of w ≦ 0.5, a high strain rate S ₄₀₀₀ can be obtained without changing the temperature characteristics, whereas if the Sb substitution amount exceeds the range, As the Sb substitution amount increases, the temperature characteristics tend to change.

{X-ray diffraction pattern}
FIG. 9 shows a sintered body used in the piezoelectric / electrostrictive elements of Examples 2 to 6 in which the Sb substitution amount is w = 0.02, 0.04, 0.05, 0.06, 0.08. It is a figure which shows an X-ray diffraction pattern. FIG. 9 also shows an X-ray diffraction pattern of the sintered body in which the Sb substitution amount is w = 0.

  The sample was set so that X-rays were irradiated onto the 12 mm × 3 mm surface of the processed sample, and the X-ray diffraction pattern of the sample was measured in the range of 20 ° to 60 ° by the 2θ / θ method. The X-ray diffraction pattern was measured using an X-ray diffractometer with a Cu-Kα ray as a radiation source and a graphite monochromator installed in front of the detector. X-ray generation conditions were measured as 35 kV-30 mA, scan width 0.02 °, scan speed 2 ° / min, diverging slit 1 °, and light receiving slit 0.3 mm, and the intensity ranged from 2θ = 44 ° to 47 °. It was confirmed that two large peaks were present. At this time, when the peak intensity on the high angle side is about twice the peak intensity on the low angle side, it is mainly tetragonal, the peak on the low angle side is the (002) plane, and the peak on the high angle side is (200). It can be determined as a surface.

  As shown in FIG. 9, when the Sb substitution amount is in the range of 0 ≦ w ≦ 0.06, an X-ray diffraction pattern specific to the tetragonal perovskite is observed, and the crystal system of the sintered body is a tetragonal crystal. I understand that. On the other hand, when the Sb substitution amount is w = 0.08, an X-ray diffraction pattern unique to the orthorhombic perovskite is observed, and it can be seen that the crystal system of the sintered body is orthorhombic.

  In Tables 1 to 3, the X-ray diffraction patterns of the sintered bodies used in the piezoelectric / electrostrictive elements of Examples 1 to 21 and Comparative Examples 1 to 8 are found in the range of 2θ = 44 to 47 °. Also shown is a lattice strain parameter, which is the ratio of the two face spacings calculated from the two strong peaks by the half-width midpoint method. This “lattice strain parameter” is an index value representing the degree of lattice strain. When the crystal system is a tetragonal system, it generally means the ratio of the (002) plane spacing to the (200) plane spacing. To do.

  As shown in Examples 1 to 7 and Comparative Example 1, the lattice strain parameter decreases as the Sb substitution amount increases, and is 1.003 when the Sb substitution amount is within the range of 0.01 ≦ w ≦ 0.10. It is 1.025 or less.

In the (Li, Na, K) (Nb, Ta, Sb) O ₃ -based piezoelectric / electrostrictive porcelain composition, the crystal system is tetragonal or oblique even if the composition is other than the compositions of Examples 2 to 6. If the tetragonal and lattice strain parameters are 1.003 or more and 1.02 or less, the domain can be easily rotated, and the distortion rate _S4000 can be improved. This is inferred from the fact that the increase in the strain rate S ₄₀₀₀ is larger in Tables 1 and 2 than the increase in the piezoelectric constant. In fact, even in the strain ratio S ₄₀₀₀ good examples 9 to 21, the lattice strain parameter, which is 1.003 or more 1.025 or less.

Further, as shown in FIG. 8, when the Sb substitution amount is in the range of 0 ≦ w ≦ 0.06, no peak derived from a heterogeneous phase is observed, but when the Sb substitution amount is w = 0.08, Peaks derived from the different phases shown are observed. This heterogeneous phase is considered to be LiSbO ₃ . When the polished surface of the sintered body used in the piezoelectric / electrostrictive element of Example 6 was observed with a scanning electron microscope (SEM), needle crystals were observed, and the constituent elements of the needle crystals were EDS. Analysis with an energy dispersive X-ray spectrometer revealed that it contained a large amount of Sb. This confirms that the heterophasic peak observed in the X-ray diffraction pattern is derived from LiSbO ₃ .

The Sb substitution amount at which such a peak derived from a different phase is observed varies slightly depending on the composition of the perovskite oxide and the amount of Mn compound added. However, when the Sb substitution amount is in the range of 0 ≦ w ≦ 0.05, such a peak derived from a different phase is observed regardless of the composition of the perovskite oxide and the addition amount of the Mn compound. Absent. Actually, in Examples 9 to 11, 13 to 15, and 17 to 21, no LiSbO ₃ heterogeneous phase was observed.

Next, the phase transition temperature T _OT of the sintered bodies used in the piezoelectric / electrostrictive elements of Examples 1 to 21 and Comparative Examples 1 to 8 was measured. The measurement results are shown in Tables 1 to 3. The phase transition temperature T _OT was determined by measuring the temperature dependence of the relative dielectric constant ε / ε ₀ with an impedance analyzer. As apparent from the measurement results, when the Sb substitution amount is in the range of 0.01 ≦ w ≦ 0.05, the phase transition temperature _TOT is hardly changed, as described in the explanation of FIG. The distortion rate S ₄₀₀₀ can be increased overall without changing the temperature characteristics. However, if the Sb substitution amount exceeds this range, the phase transition temperature increases, as a result, strain ratio S ₄₀₀₀ at room temperature by a temperature characteristic changes is reduced. Such an increase in the phase transition temperature T _OT is considered to be caused by the occurrence of a different phase of LiSbO ₃ causing a decrease in the amount of Li contained in the perovskite phase.

  The above description is illustrative in all aspects, and the present invention is not limited thereto. It is understood that countless variations that are not illustrated can be envisaged without departing from the scope of the present invention.

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. It is a figure which shows the temperature change of a distortion. It is a figure which shows the X-ray-diffraction pattern of a sintered compact.

Explanation of symbols

1, 2, 3, 4 Piezoelectric / electrostrictive actuators 122, 222, 224, 402 Piezoelectric / electrostrictive film 121, 123, 221, 223, 225 Electrode film 404 Internal electrode film

Claims (5)

General formula {Li _y (Na _1-x K _x ) _1-y } _a (Nb _1-z-w Ta _z Sb _w ) O ₃ A, x, y, z, and w are 1 <a ≦ 1.05, 0.30 ≦ x ≦ 0.70, 0.02 ≦ y ≦ 0.10, and 0 ≦ z ≦ 0, respectively. Perovskite oxide having a composition satisfying .5 and 0.01 ≦ w ≦ 0.1;
A Mn compound added to the perovskite oxide;
Consists of
Mn is not taken into the crystal lattice of the perovskite oxide,
The amount of the Mn compound added to 100 mol parts of the perovskite oxide is 0.001 mol part or more and 0.1 mol part or less in terms of Mn atoms.
Piezoelectric / electrostrictive porcelain composition. General formula {Li _y (Na _1-x K _x ) _1-y } _a (Nb _1-z-w Ta _z Sb _w ) O ₃ A, x, y, z, and w are 1 <a ≦ 1.05, 0.30 ≦ x ≦ 0.70, 0.02 ≦ y ≦ 0.10, and 0 ≦ z ≦ 0, respectively. Perovskite oxide having a composition satisfying .5 and 0.01 ≦ w ≦ 0.1;
A Mn compound added to the perovskite oxide;
Consists of
In an X-ray diffraction pattern using Cu—Kα ray as an X-ray source, a surface obtained from a peak on the high angle side among two main peaks derived from the perovskite compound found in a range of 2θ = 44 to 47 ° The ratio of the surface interval obtained from the low angle side peak to the interval is 1.003 or more and 1.025 or less,
Mn is not taken into the crystal lattice of the perovskite oxide,
The amount of the Mn compound added to 100 mol parts of the perovskite oxide is 0.001 mol part or more and 0.1 mol part or less in terms of Mn atoms.
Piezoelectric / electrostrictive porcelain composition. LiSbO ₃ The piezoelectric / electrostrictive porcelain composition according to claim 1 or 2, wherein the piezoelectric / electrostrictive ceramic composition according to claim 1 or 2 is not contained. A piezoelectric / electrostrictive film, which is a sintered body of the piezoelectric / electrostrictive ceramic composition according to any one of claims 1 to 3,
Electrode films on both principal surfaces of the piezoelectric / electrostrictive film;
A piezoelectric / electrostrictive element comprising: The piezoelectric / electrostrictive film is LiSbO. ₃ The piezoelectric / electrostrictive element according to claim 4, which does not include the different phase.

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