JP2013189325A - Method for manufacturing piezoelectric/electrostrictive material film, and powder composition used for manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a piezoelectric/electrostrictive material film having high characteristics with an intended composition using simple steps, the piezoelectric/electrostrictive material film being composed of tetragonal perovskite that is expressed by a general formula ABO(wherein, 0.90≤x≤1.20, and δ represents the amount of excess oxygen or the amount of deficient oxygen and may be 0) and having a basic composition in which site A includes Li, Na and K, and site B includes Nb and/or Sb.SOLUTION: A raw material powder is prepared that contains constituent elements of a basic composition, such that the Li content in terms of molar ratio is twice or more the amount of the basic composition. The raw material powder is calcined, and the calcined material composed of a main phase composed of orthorhombic perovskite and a heterogeneous phase composed of at least LiNbOand/or LiSbOis formed. The calcined material is pulverized, and a film containing the obtained calcined/pulverized powder is formed on a substrate. The film is baked at 950°C or more, and a piezoelectric/electrostrictive material film composed of tetragonal perovskite is formed.

Description

  The present invention relates to a method for producing a piezoelectric / electrostrictive film and a powder composition used for the production.

  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. There are also advantages such as high power, fast response speed, high durability, and low power consumption. Taking advantage of these advantages, they are employed in inkjet printer heads, diesel engine injectors, and the like.

  Conventionally, lead zirconate titanate (PZT) -based compositions have been used as piezoelectric / electrostrictive porcelain compositions for piezoelectric / electrostrictive actuators. However, although PZT has high strain characteristics, it contains lead, which is a harmful substance, and therefore, the influence of elution of lead from the sintered body on the global environment has been strongly concerned.

Thus, in recent years, alkali niobate-based piezoelectric / electrostrictive porcelain compositions have been proposed. For example, in Patent Document 1, the composition formula is Li _x (K _1-y Na _y ) _1-x (Nb _1-z Ta _z ) O ₃ (however, 0.001 ≦ x ≦ 0.2, 0 ≦ y An alkali metal-containing niobium oxide piezoelectric material composition comprising a solid solution represented by ≦ 0.8 and 0 <z ≦ 0.4) is disclosed. Patent Document 2 includes a general formula: {Li _x (K _1−y Na _y ) _1−x } {Nb _1−z−w Ta _z Sb _w } O ₃ (where 0 ≦ x ≦ 0.2, 0 ≦ y ≦ 1, 0 ≦ z ≦ 0.4, 0 ≦ w ≦ 0.2, x + z + w> 0), and a polycrystal having an isotropic perovskite compound as a main phase. A crystal-oriented ceramic in which specific crystal planes of crystal grains constituting a crystal body are oriented is disclosed. Non-Patent Document 1 discloses that a (Li, Na, K) (Nb, Ta) O ₃ piezoelectric material achieves piezoelectric characteristics comparable to PZT while being non-lead. Non-Patent Document 2 describes a lead-free high-temperature piezoelectric ceramic having good [Li _x (Na _0.5 K _0.5 ) _1-x ] NbO ₃ (0.04 ≦ x ≦ 0.20) to which lithium is added. It is disclosed that there is. The piezoelectric / electrostrictive bodies disclosed in these documents are all in bulk form.

On the other hand, a piezoelectric thin film element using a film-type piezoelectric / electrostrictive body is also known. For example, in Patent Document 3, in a piezoelectric thin film element in which a lower electrode, a piezoelectric thin film, and an upper electrode are arranged on a substrate, the piezoelectric thin film is (Na _x1 K _y1 Li _z1 ) NbO ₃ (0 <x1 <1, 0. 4 <y1 <1, 0 ≦ z1 <1, x1 + y1 + z1 = 1), which is a dielectric thin film having an alkali niobium oxide perovskite structure, and (Na _x2 K _y2 Li between the lower electrode and the piezoelectric thin film) _z2 ) an underlayer dielectric thin film of an alkali niobium oxide perovskite structure represented by NbO ₃ (0 <x2 <1, 0 <y2 ≦ 0.4, 0 ≦ z2 <1, x2 + y2 + z2 = 1 and y1> y2) A piezoelectric thin film element is disclosed.

Japanese Patent No. 3531803 Japanese Patent No. 4326374 Japanese Patent No. 4258530

Y. Saito et.al., Nature 432, 84-87 (2004) Y. Guo et al., App. Phys. Lett. 85 (2004) 4121 P. C. Goh et. Al., Appl. Phys. Lett. 99 (2011) 092902

However, a piezoelectric film-type element obtained by forming a (Li, Na, K) (Nb, Ta, Sb) O ₃ -based non-lead piezoelectric film cannot fully exhibit the inherent properties of the material. As mentioned in Non-Patent Document 3 (PC Goh et. Al., Appl. Phys. Lett. 99 (2011) 092902), lithium is applied to the lower electrode (for example, a platinum film) during the heat treatment (during firing). ) And diffuses into the substrate (eg, zirconium oxide), and as a result, the lithium concentration in the (Li, Na, K) (Nb, Ta, Sb) O ₃ -based lead-free piezoelectric film is significantly reduced. it is conceivable that. That is, lithium is an element necessary for making a (Li, Na, K) (Nb, Ta, Sb) O ₃ -based non-lead piezoelectric material into a tetragonal crystal having high piezoelectric characteristics. By diffusing into the substrate through the grain boundary or the like, the lithium concentration of the (Li, Na, K) (Nb, Ta, Sb) O ₃ -based lead-free piezoelectric film is lowered, and the orthorhombic crystal having low characteristics It is considered that. For this reason, it is considered that the performance of the piezoelectric element formed into a film is lower than the characteristics expected from the initial charged composition.

The inventors of the present invention have recently used Li ₃ NbO ₄ and / or Li ₃ SbO ₄ as a different phase in addition to orthorhombic perovskite as a main phase, using a raw material powder containing excessive lithium with respect to a target composition. Preliminary calcined / ground powder is prepared, and a simple process of forming a piezoelectric / electrostrictive film on the substrate using the calcined / ground powder has a characteristic of tetragonal perovskite according to the target composition. The knowledge that a high piezoelectric / electrostrictive film can be manufactured was obtained.

  Accordingly, an object of the present invention is to provide a production method and a powder composition therefor, which can produce a piezoelectric / electrostrictive film having high characteristics and comprising a tetragonal perovskite as a target composition containing a desired amount of lithium in a simple process. It is to provide.

According to one embodiment of the present invention, it is represented by the general formula A _x BO _{3 ± δ} (where 0.90 ≦ x ≦ 1.20, δ represents an oxygen excess or oxygen deficiency, but may be 0). A method for producing a piezoelectric / electrostrictive film comprising a tetragonal perovskite having a basic composition in which an A site contains Li, Na, and K and a B site contains Nb and / or Sb,
Preparing a raw material powder containing constituent elements of the basic composition such that the amount of Li is twice or more in molar ratio to the basic composition;
Calcining the raw material powder to form a calcined product composed of a main phase composed of orthorhombic perovskite and a heterogeneous phase composed of at least Li ₃ NbO ₄ and / or Li ₃ SbO ₄ ;
Crushing the calcined product to obtain a calcined / pulverized powder;
Forming a film containing the calcined / ground powder on a substrate;
And baking the coating at 950 ° C. or higher to form a piezoelectric / electrostrictive film made of tetragonal perovskite.

According to another aspect of the present invention, the general formula A _x BO _{3 ± δ} (where 0.90 ≦ x ≦ 1.20, δ represents an oxygen excess or oxygen deficiency, but may be 0) Production of a powder composition used for production of a piezoelectric / electrostrictive film composed of tetragonal perovskite having a basic composition in which the A site contains Li, Na and K and the B site contains Nb and / or Sb A method,
Preparing a raw material powder containing constituent elements of the basic composition so that the amount of Li is twice or more in molar ratio to the basic composition;
Calcining the raw material powder to form a calcined product comprising a main phase composed of orthorhombic perovskite and a heterogeneous phase composed of Li ₃ NbO ₄ and / or Li ₃ SbO ₄ ;
And a step of pulverizing the calcined product to obtain a calcined / pulverized powder.

According to yet another aspect of the present invention, the general formula A _x BO _{3 ± δ} (where 0.90 ≦ x ≦ 1.20, δ represents an oxygen excess or oxygen deficiency, but may be 0) And a powder composition used for manufacturing a piezoelectric / electrostrictive film comprising a tetragonal perovskite having a basic composition in which the A site contains Li, Na and K and the B site contains Nb and / or Sb. There,
A main phase composed of orthorhombic perovskite containing the constituent elements of the basic composition;
A powder composition comprising at least a heterogeneous phase composed of Li ₃ NbO ₄ and / or Li ₃ SbO ₄ is provided.

FIG. 3 is a schematic cross-sectional view of a single layer type piezoelectric / electrostrictive actuator. It is a schematic cross section of a modification of the piezoelectric / electrostrictive actuator shown in FIG. 1A. It is a schematic cross section of a multilayer type piezoelectric / electrostrictive actuator. It is a schematic cross section of a modification of the piezoelectric / electrostrictive actuator shown in FIG. 2A. It is a schematic cross section of a multilayer type piezoelectric / electrostrictive actuator. FIG. 3B is a schematic cross-sectional view of a modified example of the piezoelectric / electrostrictive actuator shown in FIG. 3A.

Method for Manufacturing Piezoelectric / Electrostrictive Film The method according to the present invention has a general formula A _x BO _{3 ± δ} (where 0.90 ≦ x ≦ 1.20, δ represents an oxygen excess amount or an oxygen deficiency amount, but 0 In which the A site contains Li, Na, and K, and the B site contains Nb and / or Sb. The piezoelectric / electrostrictive film is made of tetragonal perovskite. . The basic composition represented by this general formula includes both stoichiometric and non-stoichiometric compositions. However, even with the latest equipment, oxygen excess or oxygen deficiency (δ) can be analyzed and in light of the circumstances that can not be quantified, but that may be abbreviated as customary a _x BO _3. In any case, it is considered that there is no problem if 0 ≦ δ <1. Thus, the piezoelectric / electrostrictive film of the present invention has a (Li, Na, K) (Nb, Sb) O ₃ -based stoichiometric composition and non-stoichiometric composition, and such composition By producing a piezoelectric / electrostrictive film made of tetragonal perovskite according to the target composition, excellent piezoelectric / electrostrictive characteristics can be exhibited while being lead-free.

  In the above general formula, the A site may further contain at least one A site substitution element selected from the group consisting of Bi, Ba, Sr, Ca, La, Ce, Nd, Sm, Dy, Ho, Yb, and Ag. Good. These A site substitution elements preferably occupy 0.5 atomic percent or less of all atoms constituting the A site, more preferably 0.2 atomic percent or less, and even more preferably 0.1 atomic percent or less. is there.

  In the above general formula, the B site may further contain at least one B site substitution element selected from the group consisting of Ta, Ti, Zr, V, Cr, Fe, Co, and Ni, and is more preferably Ta. These B site substitution elements preferably occupy 50 atomic percent or less of all atoms constituting the B site, more preferably 25 atomic percent or less, and even more preferably 15 atomic percent or less.

  In the above general formula, the ratio x of the atoms constituting the A site to the atoms constituting the B site is 0.90 ≦ x ≦ 1.20, but preferably 1 ≦ x ≦ 1.20. Preferably 1 <x ≦ 1.05. As described above, when the atoms constituting the A site are richer than the atoms constituting the B site, high piezoelectric / electrostrictive characteristics are easily obtained, but the stoichiometric composition is caused by excess alkali metal. It is easier to produce a heterogeneous phase than the alkali element, thereby diffusing the alkali element into the substrate. In this regard, according to the method of the present invention, by using a calcined / ground powder containing a specific heterogeneous phase having heat resistance, it is possible to suppress loss due to diffusion of alkali elements into the substrate, A piezoelectric / electrostrictive film made of tetragonal perovskite according to the target composition can be manufactured.

  The piezoelectric / electrostrictive film may further include at least one selected from the group consisting of Mn, Cu, and Zn. These elements contribute to improvement of densification. All of Mn, Cu and Zn tend not to be dissolved in the B site of the perovskite but to be included in the heterogeneous phase or the grain boundary phase. However, the present invention is not necessarily limited to this and may be included in any part of the film. Good.

Preparation of Raw Material Powder In the method of the present invention, first, the amount of lithium is 2 in molar ratio to the basic composition of the piezoelectric / electrostrictive film to be finally obtained (hereinafter referred to as the target basic composition). A raw material powder containing constituent elements of the basic composition is prepared so as to be twice or more. Such raw material powder is preferably obtained by weighing the raw material powder at a blending ratio such that the constituent metal elements other than lithium satisfy the element ratio of the target basic composition and lithium is in a predetermined excess ratio. However, the present invention is not limited to this as long as a piezoelectric / electrostrictive film composed of tetragonal perovskite is finally obtained. The target basic composition is a composition corresponding to tetragonal perovskite, but the raw material powder containing an excessive amount of lithium in a molar ratio of 2 times or more with respect to this basic composition is the main phase by calcining. In addition to orthorhombic perovskite, a calcined product containing a heterogeneous phase composed of at least Li ₃ NbO ₄ and / or Li ₃ SbO ₄ can be provided.

As described above, lithium is an element necessary for making a (Li, Na, K) (Nb, Ta, Sb) O ₃ -based non-lead piezoelectric body into a tetragonal crystal having high piezoelectric characteristics. Diffusing into the substrate through the crystal grain boundaries, etc., the lithium concentration of the (Li, Na, K) (Nb, Ta, Sb) O ₃ -based lead-free piezoelectric film is lowered, and the low characteristic of Tend to be tetragonal. Such diffusion of lithium into the substrate is likely to occur particularly when LiNbO ₃ is included as a different phase. In this regard, the heterogeneous phase composed of at least Li ₃ NbO ₄ and / or Li ₃ SbO ₄ that is positively generated in the calcining process of the present invention has higher heat resistance than that of the heterogeneous phase such as LiNbO _3, and is about 900, for example. Since it is difficult to decompose even in a temperature range of about 1000 ° C., loss due to diffusion of lithium into the substrate can be suppressed in the firing temperature range. That is, an orthorhombic crystal in the solid-phase reaction is supplied in an amount sufficient to compensate for the loss of lithium during firing by maintaining this heat-resistant heterogeneous phase as a lithium supply source up to the firing temperature range (950 ° C. or higher). It can be efficiently supplied into the perovskite system, and as a result, it is possible to form a piezoelectric / electrostrictive film made of tetragonal perovskite. In addition, the piezoelectric / electrostrictive film thus obtained has high density.

  The raw material powder is produced by adding a dispersion medium to the raw material powder of the constituent elements (Li, Na, K, Nb, Ta, Sb, etc.) of the perovskite oxide, and then adding the raw material powder to which the dispersion medium has been added to the mortar. What is necessary is just to mix and mix by pot mills, such as a ball mill, bead mill, a hammer mill, a jet mill. 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 can be used. As the dispersion medium, an organic solvent such as ethanol, toluene, or acetone can be used. The dispersion medium is removed from the mixed slurry thus obtained by evaporation drying, filtration or the like, and a dried raw material powder is obtained.

  The raw material powder contains 2 times or more of Li in a molar ratio with respect to the target basic composition, preferably 2 to 20 times, more preferably 4 to 12 times, still more preferably 6 to 10 times. . Within such a range, the relative density of the piezoelectric / electrostrictive film after firing can be increased, thereby improving the piezoelectric characteristics of the piezoelectric / electrostrictive film.

Formation and pulverization of calcined material The calcined raw material powder is calcined, and is composed of a main phase composed of orthorhombic perovskite and a heterogeneous phase composed of at least Li ₃ NbO ₄ and / or Li ₃ SbO _4. A ceramic is formed. This calcination is carried out by heating the raw material powder to a temperature of 600 to 950 ° C., preferably 700 to 900 ° C., and then holding within this temperature range for 0 to 20 hours, preferably 30 seconds to 10 hours. Is preferred. Here, the holding time of 0 hours does not mean that the calcination is not performed, but means that the temperature is raised immediately and then cooled immediately after reaching a predetermined temperature. Further, the hetero phase may further include at least one selected from the group consisting of Li ₃ TaO ₄ and Li ₃ (Nb, Ta, Sb) O ₄ . The amount of the heterogeneous phase in the calcined product is preferably 1 to 40 mol%, more preferably 5 to 25 mol%, still more preferably 8 to 20 mol% with respect to the entire calcined product. The calcined product may contain other crystal phases having an impurity level of less than 5% by weight, preferably less than 2% by weight, more preferably less than 1% by weight.

By the way, according to a known method, the piezoelectric powder raw material before film formation is prepared by mixing raw materials, calcining and pulverization. However, due to contamination during pulverization and insufficient densification leading to performance degradation. In order to avoid the coarsening of the connected particle diameter, calcination at high temperature is not performed. As a result, the piezoelectric raw material powder is not a perovskite single phase, and LiNbO _{3, which} is liable to preferentially diffuse lithium when firing on a substrate (particularly zirconium oxide substrate) during film firing, is generated as a different phase. However, as described above, in the method of the present invention, the heterogeneous phase composed of at least Li ₃ NbO ₄ and / or Li ₃ SbO ₄ is actively generated in the calcined product, so that the Loss due to diffusion of the substrate into the substrate can be suppressed. That is, an orthorhombic crystal in the solid-phase reaction is supplied in an amount sufficient to compensate for the loss of lithium during firing by maintaining this heat-resistant heterogeneous phase as a lithium supply source up to the firing temperature range (950 ° C. or higher). It can be efficiently supplied into the perovskite system, and as a result, it is possible to form a piezoelectric / electrostrictive film made of tetragonal perovskite.

  The calcination may be performed only once or may be performed twice or more. When two or more calcinations are performed, the conditions for each calcination may be the same or different. The atmosphere at the time of calcination may be an air atmosphere or an oxygen atmosphere. It is preferable that the temperature increase rate and the temperature decrease rate during calcination are 20 to 2000 ° C./hour. The mixed raw material may be calcined with a commonly used one-stage calcining schedule (trapezoidal or acute temperature profile), may be calcined with a multi-stage calcining schedule, or It may be calcined by a three-stage calcining schedule that combines the above two-stage calcining schedules. According to a preferred embodiment of the present invention, the calcining is performed by heating the raw material powder to a temperature of 900 to 1200 ° C. at a temperature rising rate of 200 to 2000 ° C./h, and holding at this temperature for 0 to 10 minutes. It may be performed according to a temperature profile including cooling to 800 ° C. at a rate of temperature decrease of 200 to 2000 ° C./h, where the temperature profile is calculated by multiplying the temperature in the temperature region of 800 ° C. or higher by time. The temperature operation is preferably performed so that the temperature time area is 67 to 200 ° C. · h. Moreover, you may further perform the process of pre-calcining raw material powder at the temperature of 600-900 degreeC before a calcination process, and obtaining a pre-calcination thing.

  The obtained calcined product is pulverized by a ball mill or the like to obtain a calcined / pulverized powder having a desired particle size. The pulverization may be performed by a pulverization method such as mortar pulverization, pot mill, bead mill, hammer mill, jet mill, mesh or screen pressing method, and is not particularly limited. Alternatively, the perovskite-type oxide powder containing the heterogeneous phase may be synthesized by an alkoxide method or a coprecipitation method instead of the solid phase reaction method. Further, after synthesizing a solid solution of B-site elements in advance (for example, a composite oxide of a plurality of B-site elements), it is mixed with a raw material of the constituent elements of the A site and calcined, and the perovskite containing the above heterogeneous phase A type oxide powder may be synthesized.

  The volume standard D50 (median diameter) of the calcined / ground powder is preferably 0.07 to 10 μm, and more preferably 0.1 to 3 μm. Further, the calcined / ground powder may be heat treated at 400 to 850 ° C. in order to adjust the particle size of the calcined / ground powder. Since finer particles are easier to be integrated with other particles, by performing this heat treatment, a calcined / ground powder having a uniform particle size is obtained, and a sintered body having a uniform particle size is obtained.

Powder composition The calcined / pulverized powder obtained as described above has a main phase composed of orthorhombic perovskite containing constituent elements of a target basic composition, and at least Li ₃ NbO ₄ and / or Li ₃ SbO. ₄ is a powder composition comprising a heterogeneous phase composed of ₄ , and can be preferably used for the production of a piezoelectric / electrostrictive film described below.

Production of Piezoelectric / Electrostrictive Film A film containing the calcined / ground powder or powder composition is formed on a substrate. This film can be formed by various film forming methods that can use powder. The substrate on which the film is formed preferably includes an inorganic oxide base material and a lower electrode layer formed on the inorganic oxide base material, and a piezoelectric / electrostrictive film is formed on the lower electrode layer. It is formed. Further, before firing, a step of forming an intermediate electrode layer on the film containing the calcined / ground powder and further forming a film containing the calcined / ground powder on the intermediate electrode layer may be performed. Can be performed once or multiple times. An upper electrode layer may be further formed on the piezoelectric / electrostrictive film as the uppermost layer in the same manner as the intermediate electrode layer.

  The film thus formed is baked to form a piezoelectric / electrostrictive film made of tetragonal perovskite. This piezoelectric / electrostrictive film is preferably composed of a single phase of tetragonal perovskite, but also includes a crystal phase having an impurity level of less than 5% by weight, preferably less than 2% by weight, more preferably less than 1% by weight. Permissible. Since the piezoelectric / electrostrictive film thus obtained is composed of tetragonal perovskite, it exhibits high piezoelectric characteristics, and a piezoelectric / electrostrictive element such as a piezoelectric / electrostrictive actuator having high piezoelectric / electrostrictive characteristics is realized. Can do.

  Hereinafter, the manufacturing process of the piezoelectric / electrostrictive film will be described based on specific embodiments of the piezoelectric / electrostrictive actuator including the piezoelectric / electrostrictive film manufactured according to the present invention. It is not limited to the specific embodiment.

  FIG. 1A shows a schematic cross-sectional view of a single-layer piezoelectric / electrostrictive actuator 1. As shown in FIG. 1A, the piezoelectric / electrostrictive actuator 1 has a structure in which an electrode layer 121, a piezoelectric / electrostrictive film 122, and an electrode layer 123 are laminated on the upper surface of a substrate 11 in this order. The electrode layers 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 layer 121, the piezoelectric / electrostrictive film 122 and the electrode layer 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. Note that 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 layers 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.

  The piezoelectric / electrostrictive film 122 is a film made of tetragonal perovskite obtained by the production method of the present invention. 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. When the film thickness is in such a range, sufficient densification can be obtained, and the shrinkage stress during sintering does not become too large. Therefore, the thickness of the substrate 11 can be reduced to reduce the thickness of the piezoelectric / electrostrictive actuator 1. Miniaturization can be realized.

  The material of the electrode layers 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 layers 121 and 123 are preferably 15 μm or less, and more preferably 5 μm or less. When the film thickness is in such a range, the electrode layers 121 and 123 can be prevented from functioning as a relaxation layer, and a large bending displacement can be secured. In addition, in order for the electrode layers 121 and 123 to appropriately perform their roles, the film thickness of the electrode layers 121 and 123 is preferably 0.05 μm or more. The electrode layers 121 and 123 are preferably formed so as to cover regions that substantially contribute to the bending displacement of the piezoelectric / electrostrictive film 122. For example, the piezoelectric / electrostrictive film 122 is preferably 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.

  Although the material of the board | substrate 11 is ceramics, there is no restriction | limiting in the kind. 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 preferable that Among these, stabilized zirconium oxide is more preferable 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. 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 thickness of the substrate 11 is uniform. The 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. When the plate thickness is in such a range, high mechanical strength of the piezoelectric / electrostrictive actuator 1 can be secured, and the rigidity of the substrate 11 is prevented from becoming too high, and the piezoelectric / electrostrictive film at the time of voltage application is prevented. The bending displacement due to the expansion and contraction of 122 can be increased. The surface shape of the substrate 11 (the shape of the surface to which the laminate is fixed) is not particularly limited, and can 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.

  In manufacturing the piezoelectric / electrostrictive actuator 1, the electrode layer 121 is formed on the substrate 11. The electrode layer 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, dipping, or the like. . 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 layer 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 layer 121 and the formation method.

  Subsequently, the piezoelectric / electrostrictive film 122 is formed on the electrode layer 121 using the calcined / ground powder according to the present invention. Piezoelectric / electrostrictive film 122 includes 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 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 layer 123 is formed on the piezoelectric / electrostrictive film 122. The electrode layer 123 is formed in the same manner as the electrode layer 121.

  After forming the electrode layer 123, 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 layers 121 and 123 are heat-treated. The firing temperature of the piezoelectric / electrostrictive film 122 is preferably 950 ° C. or higher, more preferably 950 to 1200 ° C., and still more preferably 970 to 1100 ° C. When the temperature is in such a range, the piezoelectric / electrostrictive film 122 is sufficiently densified, and the substrate 11 and the electrode layer 121 are fixed, and the electrode layers 121 and 123 and the piezoelectric / electrostrictive film 122 are fixed. And a high piezoelectric / electrostrictive characteristic can be realized. In addition, the holding time in the firing temperature range is preferably 0 to 20 hours, more preferably 1 minute to 10 hours, and further preferably 5 minutes to 4 hours. Within this range, the piezoelectric / electrostrictive film 122 can be sufficiently densified and high piezoelectric / electrostrictive characteristics can be realized. Here, the holding time of 0 hour does not mean that the firing is not performed, but means that the temperature is raised and reaches a predetermined temperature, and then immediately cooled.

  Note that the heat treatment of the electrode layers 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 layers 121 and 123 are formed. However, when the piezoelectric / electrostrictive film 122 is fired before the heat treatment of the electrode layer 123, the electrode layer 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 having the electrode paste film printed on both main surfaces and the substrate are pressure-bonded. 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.

FIG. 1B shows a schematic cross-sectional view of a modified example of the single-layer piezoelectric / electrostrictive actuator 1.
The piezoelectric / electrostrictive actuator 1 ′ shown in FIG. 1B is a single-layer type shown in FIG. 1A except that the electrode layer 121 ′ in contact with the substrate 11 ′ is formed over a wider area than the piezoelectric / electrostrictive film 122 ′. This is the same as the piezoelectric / electrostrictive actuator 1 of FIG. According to this configuration, there is an advantage that the piezoelectric / electrostrictive film 122 ′ is unlikely to contact the substrate 11 ′, and as a result, diffusion of lithium to the substrate 11 ′ is easily suppressed.

  FIG. 2A shows a schematic cross-sectional view of the multilayer piezoelectric / electrostrictive actuator 2. As shown in FIG. 2A, the piezoelectric / electrostrictive actuator 2 includes an electrode layer 221, a piezoelectric / electrostrictive film 222, an electrode layer 223, a piezoelectric / electrostrictive film 224, and an electrode layer 225 on the upper surface of the substrate 21. It has a structure laminated in this order. The electrode layers 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 layers 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 layer 221, the piezoelectric / electrostrictive film 222, the electrode layer 223, the piezoelectric / electrostrictive film 224 and the electrode layer 225 are laminated is fixed to the substrate 21. 2A shows a case where the piezoelectric / electrostrictive film has two layers, the piezoelectric / electrostrictive film may have three or more layers. As for the thickness of the substrate 21 of the piezoelectric / electrostrictive actuator 2, the central portion 215 to which the laminated body 22 is bonded is thinner than the peripheral portion 216. Thereby, the bending displacement can be increased while maintaining the mechanical strength of the substrate 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 layers to be formed is increased.

FIG. 2B shows a schematic cross-sectional view of a modified example of the multilayer piezoelectric / electrostrictive actuator 2.
The piezoelectric / electrostrictive actuator 2 ′ shown in FIG. 2B is the multilayer type shown in FIG. 2A except that the electrode layer 221 ′ in contact with the substrate 21 ′ is formed over a wider area than the piezoelectric / electrostrictive film 222 ′. Similar to the piezoelectric / electrostrictive actuator 2. According to this configuration, there is an advantage that the piezoelectric / electrostrictive film 222 ′ is less likely to contact the substrate 21 ′, and as a result, diffusion of lithium to the substrate 21 ′ is easily suppressed.

  FIG. 3A shows a schematic cross-sectional view of the multilayer piezoelectric / electrostrictive actuator 3. As shown in FIG. 3A, the piezoelectric / electrostrictive actuator 3 includes a substrate 31 on which a unit structure having the same structure as the substrate 21 of the third embodiment is repeated. On each of the unit structures of the substrate 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 layers are increased. The

  FIG. 3B shows a schematic cross-sectional view of a modification of the multilayer piezoelectric / electrostrictive actuator 3. The piezoelectric / electrostrictive actuator 3 ′ shown in FIG. 3B is the multilayer type shown in FIG. 3A except that the electrode layer 321 ′ in contact with the substrate 31 ′ is formed over a wider area than the piezoelectric / electrostrictive film 322 ′. The same as the piezoelectric / electrostrictive actuator 3. According to this configuration, there is an advantage that the piezoelectric / electrostrictive film 322 'is unlikely to contact the substrate 31', and as a result, diffusion of lithium to the substrate 31 'is easily suppressed.

  The invention is further illustrated by the following examples.

Example 1: Production of Piezoelectric / Electrostrictive Film and Piezoelectric / Electrostrictive Actuator Piezoelectric / electrostrictive films having various target compositions shown in Samples 1 to 16 in Table 1 were produced by the following procedure.

(1) Preparation of calcined / ground powder 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 ) and tantalum oxide (Ta ₂ O ₅ ) raw material powders were prepared. These powders were weighed so that a metal element other than Li gives the “target composition of the piezoelectric / electrostrictive film” shown in Table 1, but the amount of Li added was the Li excess ratio shown in Table 1. . At that time, for comparison, Samples 1 to 4 were weighed according to the target composition with an excess Li ratio of 1. Subsequently, alcohol was added as a dispersion medium to the weighed raw material powders 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 calcined powder containing a perovskite oxide as a main phase. Subsequently, the calcined powder was coarsely pulverized and then passed through a 100 mesh sieve to adjust the particle size. Thus, a calcined / ground powder containing a perovskite oxide as a main phase was obtained.

The X-ray diffraction pattern of the calcined / ground powder obtained was measured with an X-ray diffractometer (Bulker AXS, D8ADVANCE) under the following conditions, and subjected to Rietveld analysis (analysis software: Bruker AXS, TOPAS). Thus, the crystal structure and the amount of different phases contained in the calcined / ground powder were analyzed.
-X-ray output: 40 kV x 40 mA
-Goniometer radius: 250mm
-Divergent slit: 0.6 °
-Scattering slit: 0.6 °
-Light receiving slit: 0.2mm
-Solar slit: 4 ° (incident side, light receiving side)
-Measurement method: 2θ / θ method using a sample horizontal type concentrated optical system (2θ = 20-60 ° is measured, step width is 0.01 °)
As a result, in addition to the orthorhombic perovskite that is the main phase, the presence of a heterogeneous phase composed of LiNbO ₃ was confirmed for samples 1 to 4, whereas the samples were added to the orthorhombic perovskite that was the main phase. Thus, the presence of a heterogeneous phase composed of Li ₃ NbO ₄ was confirmed.

(2) Production of Piezoelectric / Electrostrictive Actuator Using the obtained perovskite calcined / ground powder, a piezoelectric / electrostrictive actuator 1 ′ shown in FIG. 1B was produced. First, a platinum paste was screen-printed on a stabilized zirconium oxide substrate as the substrate 11 ′, and a platinum electrode layer 121 ′ was formed by heat treatment. Next, an unfired piezoelectric / electrostrictive film 122 ′ was formed on the platinum electrode layer 121 ′ by screen printing a paste prepared by mixing calcined / ground powder with a binder. Subsequently, a composition composed of the base material 11 ′, the platinum electrode layer 121 ′ and the unfired piezoelectric / electrostrictive film 122 ′ was housed in an alumina container and fired at 1050 ° C. for 3 hours. Subsequently, a gold paste was screen printed on the fired piezoelectric / electrostrictive film 122 ′, and a gold electrode layer 123 ′ was formed by heat treatment. Thus, a piezoelectric / electrostrictive actuator provided with a piezoelectric / electrostrictive film made of tetragonal perovskite was obtained.

Example 2 Evaluation of Piezoelectric / Electrostrictive Films The piezoelectric / electrostrictive films of Samples 1 to 16 prepared in Example 1 were evaluated as follows.

(1) Crystal structure analysis The X-ray diffraction pattern of the fired piezoelectric / electrostrictive film element was measured with an X-ray diffractometer (Bulker AXS, D8ADVANCE) under the following conditions to analyze the crystal structure.
-X-ray output: 40 kV x 40 mA
-Goniometer radius: 250mm
-Divergent slit: 0.6 °
-Scattering slit: 0.6 °
-Light receiving slit: 0.2mm
-Solar slit: 4 ° (incident side, light receiving side)
-Measurement method: 2θ / θ method using a sample horizontal type concentrated optical system (2θ = 20-60 ° is measured, step width is 0.01 °)

(2) Surface microstructure observation After the surface of the fired piezoelectric / electrostrictive element was sputtered with an ion sputtering apparatus (JFC-1500, manufactured by JEOL Ltd.) to a thickness of about 10 nm, the surface The microstructure was observed with a scanning electron microscope (JSM-6390, manufactured by JEOL Ltd.) to obtain a secondary electron image.

(3) Cross-sectional microstructure observation and elemental analysis The piezoelectric / electrostrictive film element was mechanically polished, and the cross section of the piezoelectric / electrostrictive film element was observed with FE-EPMA (JXA-8530F, manufactured by JEOL Ltd.). The degree of densification of the film was evaluated. In addition, elemental analysis was performed to calculate the composition of elements other than lithium.

(4) Lithium concentration analysis Li-direction analysis of the piezoelectric / electrostrictive film element after firing was performed using D-SIMS (manufactured by CAMCA, IMS-6f), and the lithium concentration of the piezoelectric / electrostrictive film was Was calculated.

(5) Measurement of relative density From the cross-sectional photograph of the piezoelectric / electrostrictive film obtained in (3) above, using image editing software (trade name “Image-Pro”, manufactured by Media Cybernetics), the pore portion The relative density of the piezoelectric / electrostrictive film was evaluated.

  The obtained results were as shown in Table 1. In Table 1, the crystal system of the obtained piezoelectric / electrostrictive film was determined by the above (1), the Li amount was determined by the above (4), and the obtained piezoelectric / electrostrictive film was The final composition of the strained film is determined based on the evaluation results (3) and (4) above. As can be seen from Table 1, in Samples 5 to 16 produced using the raw material having an excess of Li according to the method of the present invention, a piezoelectric / electrostrictive film having high characteristics according to the target composition made of tetragonal perovskite. was gotten. On the other hand, in the samples 1 to 4 produced without following the method of the present invention, piezoelectric / electrostrictive films having low characteristics made of orthorhombic perovskite were obtained. Moreover, as can be seen from the results of Samples 9 to 16 produced using various Li excess ratios, the Li excess ratio in the raw material powder is preferable in that the samples 10 to 14 having 4 to 12 exhibit a high relative density, and more Samples 11 to 13 having a Li excess ratio of 6 to 10 and exhibiting a relative density of 95% or more are preferable. Such a high relative density results in high piezoelectric properties. In addition, it is surmised that the excess lithium escaped out of the film through evaporation and diffusion to the substrate.

Example 3: a powder of example Motogenryo using other heterogeneous phase, except that antimony oxide and _(Sb 2 _{O 3)} was added, the heterogeneous phase of the calcined / crushed powder was produced as _Li 3 SbO _4, Example 1 and The piezoelectric / electrostrictive film was prepared and evaluated in the same manner as in 2. As a result, in the same manner as in Examples 1 and 2, a piezoelectric / electrostrictive film having high characteristics as a target composition made of tetragonal perovskite was obtained.

1,1 ′, 2,2 ′, 3,3 ′ Piezoelectric / electrostrictive actuator 11,11 ′, 21,21 ′, 31,31 ′ Substrate 122,122 ′, 222,224,222 ′, 224 ′, 322 , 324, 322 ', 324' Piezoelectric / electrostrictive film 121, 121 ', 123, 123', 221, 221 ', 223, 223', 225, 225 ', 321, 321', 323, 323 ', 325 , 325 'electrode layer

Claims (21)

It is represented by the general formula A _x BO _{3 ± δ} (where 0.90 ≦ x ≦ 1.20, δ represents oxygen excess or oxygen deficiency, but may be 0), and the A site is Li, Na and A method for producing a piezoelectric / electrostrictive film comprising a tetragonal perovskite having a basic composition containing K and having a B site containing Nb and / or Sb,
Preparing a raw material powder containing constituent elements of the basic composition such that the amount of Li is twice or more in molar ratio to the basic composition;
Calcining the raw material powder to form a calcined product composed of a main phase composed of orthorhombic perovskite and a heterogeneous phase composed of at least Li ₃ NbO ₄ and / or Li ₃ SbO ₄ ;
Crushing the calcined product to obtain a calcined / pulverized powder;
Forming a film containing the calcined / ground powder on a substrate;
And baking the film at 950 ° C. or higher to form a piezoelectric / electrostrictive film made of tetragonal perovskite.   The method according to claim 1, wherein the raw material powder contains Li in a molar ratio of 2 to 20 times the basic composition.   The method according to claim 1 or 2, wherein the raw material powder contains Li in a molar ratio of 4 to 12 times the basic composition.   In the general formula, the A site further contains at least one A site substitution element selected from the group consisting of Bi, Ba, Sr, Ca, La, Ce, Nd, Sm, Dy, Ho, Yb, and Ag. The method as described in any one of Claims 1-3.   The method according to claim 4, wherein the A site substitution element accounts for 0.5 atomic% or less of all atoms constituting the A site.   In the general formula, the B site further includes at least one B site substitution element selected from the group consisting of Ta, Ti, Zr, V, Cr, Fe, Co, and Ni. The method according to item.   The method according to claim 6, wherein the B site substitution element is Ta.   The method according to claim 6 or 7, wherein the B site substitution element occupies 50 atomic% or less of all atoms constituting the B site.   The method according to claim 1, wherein 1 <x ≦ 1.05 in the general formula.   The method according to claim 1, wherein the piezoelectric / electrostrictive film further includes at least one selected from the group consisting of Mn, Cu, and Zn. The method according to claim 1, wherein the heterogeneous phase further includes at least one selected from the group consisting of Li ₃ TaO ₄ and Li ₃ (Nb, Ta, Sb) O ₄ .   The said calcining is performed by heating the said raw material powder to the temperature of 600-950 degreeC, and hold | maintaining for 0 to 20 hours within this temperature range, The method as described in any one of Claims 1-11. .   The method according to any one of claims 1 to 12, wherein the baking is performed by heating the coating to a temperature of 950 to 1200 ° C and then holding the coating within the temperature range for 0 to 20 hours.   The method according to claim 1, wherein the coating is formed by a screen printing method.   The substrate includes an inorganic oxide base material and a lower electrode layer formed on the inorganic oxide base material, and the piezoelectric / electrostrictive film is formed on the lower electrode layer. 15. A method according to any one of claims 1-14.   The method according to claim 15, wherein the inorganic oxide substrate comprises at least one selected from the group consisting of zirconium oxide, aluminum oxide, magnesium oxide, mullite, aluminum nitride, silicon nitride, and glass.   The method of claim 15, wherein the inorganic oxide substrate comprises zirconium oxide.   The lower electrode layer comprises at least one selected from the group consisting of at least one metal selected from platinum, palladium, rhodium, gold and silver, or an alloy of two or more metals selected from the group. The method according to any one of claims 15 to 17.   Forming the intermediate electrode layer on the coating containing the calcined / ground powder before the firing, and further forming the coating containing the calcined / ground powder on the intermediate electrode layer, The method according to any one of claims 1 to 18, which is performed once or a plurality of times. It is represented by the general formula A _x BO _{3 ± δ} (where 0.90 ≦ x ≦ 1.20, δ represents oxygen excess or oxygen deficiency, but may be 0), and the A site is Li, Na and A method for producing a powder composition used for producing a piezoelectric / electrostrictive film comprising a tetragonal perovskite having a basic composition containing K and containing a B site containing Nb and / or Sb,
Preparing a raw material powder containing constituent elements of the basic composition so that the amount of Li is twice or more in molar ratio to the basic composition;
Calcining the raw material powder to form a calcined product comprising a main phase composed of orthorhombic perovskite and a heterogeneous phase composed of Li ₃ NbO ₄ and / or Li ₃ SbO ₄ ;
And crushing the calcined product to obtain a calcined / pulverized powder. It is represented by the general formula A _x BO _{3 ± δ} (where 0.90 ≦ x ≦ 1.20, δ represents oxygen excess or oxygen deficiency, but may be 0), and the A site is Li, Na and A powder composition used for the production of a piezoelectric / electrostrictive film comprising a tetragonal perovskite having a basic composition containing K and having a B site containing Nb and / or Sb,
A main phase composed of orthorhombic perovskite containing the constituent elements of the basic composition;
A powder composition comprising at least a heterogeneous phase composed of Li ₃ NbO ₄ and / or Li ₃ SbO ₄ .

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