Piezoelectric ceramic laminate

Abstract

To provide a piezoelectric ceramic laminate capable of improving strength.SOLUTION: The present invention relates to a piezoelectric ceramic laminate in which piezoelectric ceramic layers and internal electrodes are alternately laminated. The piezoelectric ceramic layer comprises a crystal phase composed of an alkali niobate-based perovskite oxide having piezoelectric properties. The internal electrode contains silver (Ag) and a content of silver (Ag) in the piezoelectric ceramic layer obtained by elemental analysis using SEM-EDX is 0.67 wt.% or more and 2.02 wt.% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to piezoelectric ceramic laminates. [Background technology]

[0002] Patent Document 1 discloses a lead-free piezoelectric ceramic composition. This lead-free piezoelectric ceramic composition includes a main phase formed of a first crystalline phase made of a niobium / alkali tantalate-based perovskite oxide having piezoelectric properties, and a subphase including a second crystalline phase made of an M-Ti-O-based spinel compound (element M is a monovalent, trivalent, or tetravalent element). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2014 / 156015 Summary of the Invention [Problem to be solved by the invention]

[0004] The lead-free piezoelectric ceramic composition of Patent Document 1 is a difficult-to-sinter body and has a relatively low specific gravity. This lead-free piezoelectric ceramic composition has abnormal growth in some parts, which increases the particle size and reduces the strength. The present disclosure has been made in view of the above circumstances, and aims to provide a piezoelectric ceramic laminate that can improve strength. The present disclosure can be realized in the following aspects. [Means for solving the problem]

[0005] [1] A piezoelectric ceramic laminate in which piezoelectric ceramic layers and internal electrodes are alternately laminated, the piezoelectric ceramic layer contains a crystalline phase made of an alkali niobate perovskite oxide having piezoelectric properties; The internal electrodes contain silver (Ag), The silver (Ag) content in the piezoelectric ceramic layer obtained by elemental analysis using SEM-EDX is 0.67% by weight or more and 2.02% by weight or less. Piezoelectric ceramic laminate.

[0006] [2] The silver (Ag) content in the piezoelectric ceramic layer obtained by elemental analysis using SEM-EDX is 1.65% by weight or more and 2.02% by weight or less. The piezoelectric ceramic laminate according to [1].

[0007] [3] The average particle size of the crystal grains of the crystalline phase is 2.25 μm or less. The piezoelectric ceramic laminate according to [1] or [2]. [Effects of the Invention]

[0008] The present disclosure can provide a piezoelectric ceramic laminate that can improve strength. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view showing a piezoelectric ceramic laminate according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is an exploded perspective view of the piezoelectric ceramic laminate of FIG. [Figure 3] FIG. 2 is a conceptual diagram illustrating a method for measuring the particle size of crystal particles of the first crystal phase. [Figure 4] 1 is a flowchart showing a method for manufacturing a piezoelectric ceramic laminate. [Figure 5] 1 is a cross-sectional SEM image of Example 1. [Figure 6] 1 is a cross-sectional SEM image of Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present disclosure will be described in detail below. In this specification, when a numerical range is indicated using "-", it is intended to include both the lower limit and the upper limit unless otherwise specified. For example, the expression "10-20" includes both the lower limit "10" and the upper limit "20". In other words, "10-20" has the same meaning as "10 or more and 20 or less". In addition, in this specification, the upper limit and lower limit of each numerical range can be combined in any way.

[0011] 1. Piezoelectric ceramic laminate 10 1 and 2 show an example of a piezoelectric ceramic laminate 10 according to this embodiment. As shown in Fig. 2, the piezoelectric ceramic laminate 10 includes a laminate 20 and a pair of side electrodes 30. The laminate 20 includes a plurality of piezoelectric ceramic layers 22 and a plurality of internal electrodes 24. In the laminate 20, the piezoelectric ceramic layers 22 and the internal electrodes 24 are alternately stacked.

[0012] In the laminate 20, the internal electrodes 24 and the piezoelectric ceramic layers 22 stacked together are referred to as drive layers 41. In the laminate 20, the piezoelectric ceramic layers 22 that are not provided with internal electrodes 24 are referred to as non-drive layers 43.

[0013] The internal electrode 24 has an extraction electrode 24A. The internal electrodes 24 are alternately stacked such that the extraction electrodes 24A face in opposite directions.

[0014] The internal electrodes 24 contain silver (Ag).

[0015] The pair of side electrodes 30 are respectively arranged on a pair of back-to-back side surfaces of the laminate 20. The pair of side electrodes 30 are respectively connected to a plurality of extraction electrodes 24A exposed from different sides of the laminate 20.

[0016] The piezoelectric ceramic layer 22 does not contain lead (Pb) and includes a main phase formed of a crystalline phase (first crystalline phase) made of an alkali niobate perovskite oxide having piezoelectric properties, and a subphase. The subphase preferably includes a crystalline phase (second crystalline phase) made of a metal oxide. Hereinafter, the first crystalline phase will also be referred to as the "main phase," and crystalline phases other than the main phase will also be referred to as "subphases."

[0017] (1) Main phase A preferred example of the alkali niobate perovskite oxide is one represented by the following composition formula (formula (1)). (K a Na b Li c M1 d ) e (M2 f )O g …(1) Here, the element M1 is one or more of calcium (Ca), strontium (Sr), and barium (Ba). The element M2 is one or more of niobium (Nb), tantalum (Ta), titanium (Ti), zirconium (Zr), and hafnium (Hf), including at least niobium (Nb). That is, the element M2 is one or more of niobium (Nb), titanium (Ti), zirconium (Zr), and hafnium (Hf). The value of g is any value that can maintain the perovskite crystal structure. That is, the amount of O atoms is set to be sufficient to maintain the perovskite crystal structure.

[0018] The typical composition of alkali niobate perovskite oxides is (K, Na, Li, Ca, Ba) e (Nb,Ti,Zr)O hand has K, Na, and Nb as its main metal components. Because this alkali niobate perovskite oxide has K, Na, and Nb as its main metal components, materials composed of alkali niobate perovskite oxide are also called "KNN" or "KNN material," and the crystalline phase composed of alkali niobate perovskite oxide is also called "KNN phase." Furthermore, materials composed of alkali niobate perovskite oxides whose main metal components are K, Na, Li, Nb, and Ca are also called "KNLNC" or "KNLNC material," and the crystalline phase composed of such materials is also called "KNLNC phase."

[0019] In the above composition formula (1), when M1 is barium (Ba) and calcium (Ca), and M2 is niobium (Nb), zirconium (Zr), and titanium (Ti), composition formula (1) can be expressed as the following composition formula (2): d = X1 + Y1, f = X2 + Y2 + Z2. (K a Na b Li c Ba X1 Ca Y1 ) e (Nb X2 Zr Y2 Ti Z2 )O g …(2)

[0020] (2) Subphase The subphase preferably includes a crystalline phase (second crystalline phase) made of one or more metal oxides selected from the following (a) to (e): (A) A-Ti-BO compound (element A is an alkali metal, and element B is at least one of Nb and Ta) (a) M3-Ti-O spinel compounds (element M is a monovalent to pentavalent metal) (U) A2B6O 13 Compounds (element A is a monovalent metal, element B is a divalent to hexavalent metal) (E) A3B5O 15 Compounds (element A is a monovalent or divalent metal, element B is a divalent or pentavalent metal) (E) Single metal oxides consisting of metal elements selected from magnesium (Mg), nickel (Ni), cobalt (Co), iron (Fe), manganese (Mn), chromium (Cr), zirconium (Zr), titanium (Ti), silver (Ag), zinc (Zn), scandium (Sc), and bismuth (Bi).

[0021] The A-Ti-BO compound is a compound containing a composite oxide of element A (potassium (K), rubidium (Rb), cesium (Cs), etc.), titanium (Ti), and element B. In the present disclosure, the A-Ti-BO compound may be one in which element A is an alkali metal, element B is at least one of Nb and Ta, and the contents of element A, element B, and Ti are all non-zero.

[0022] The A-Ti-BO compound is preferably one represented by the following composition formula (3). A 1-x3 Ti 1-x3 B 1+x3 O5…(3) Here, the element B is at least one of niobium (Nb) and tantalum (Ta), and x3 is an arbitrary value. Specific compounds according to the above composition formula include KTiNbO5, K 0.90 Ti 0.90 Nb 1.10 O5,K 0.85 Ti 0.85 Nb 1.15 O5,RbTiNbO5,Rb 0.90 Ti 0.90 Nb 1.10 O5,Rb 0.85 Ti 0.85 Nb 1.15 O5,CsTiNbO5,Cs 0.90 Ti 0.90 Nb 1.10 O5, KTiTaO5, CsTiTaO5, etc. can be used.

[0023] Among A-Ti-BO compounds, those whose main metal components are niobium (Nb), titanium (Ti), and potassium (K) are also called "NTK materials," and their crystalline phase (secondary crystalline phase) is also called "NTK phase."

[0024] As the A-Ti-BO compound, the above-mentioned A 1-x3 Ti 1-x3 B 1+x3 In addition to the compound represented by O5, the compound represented by A1Ti3B1O9 is also available.

[0025] The M3-Ti-O based spinel compound is preferably one represented by the following composition formula: M3 x4 TiO y4 …(4) Here, element M3 is a monovalent to tetravalent metal element, and is at least one of lithium (Li), magnesium (Mg), aluminum (Al), scandium (Sc), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), gallium (Ga), yttrium (Y), zirconium (Zr), tin (Sn), antimony (Sb), silicon (Si), and hafnium (Hf). When lithium (Li) is included as element M3, it is preferable that one or more metal elements other than lithium (Li) be included together with lithium (Li) so that the second crystal phase forms a spinel compound. The coefficients x4 and y4 are relative values ​​when the Ti content is set to 1. To form a spinel compound, coefficient x4 preferably satisfies 0.5≦x≦5.0. Furthermore, coefficient y4 can be any value that forms a spinel compound, but typically satisfies 2≦y4≦8. The second crystal phase, which is composed of a spinel compound, stabilizes the structure of the first crystal phase, thereby providing a piezoelectric ceramic layer 22 with excellent piezoelectric properties. From the viewpoint of piezoelectric properties, it is preferable to use a second crystal phase represented by the composition formula M32TiO4 or (M4,M5)TiO4, which contains two divalent metal elements M3. Here, elements M4 and M5 are two different metal elements contained in element M3.

[0026] It is particularly preferable that the piezoelectric ceramic layer 22 contains two or more metal elements as the element M3. In this specification, a spinel compound containing two or more metal elements as the element M3 is also referred to as a "composite spinel compound." When the second crystal phase contains a composite spinel compound, the properties of the piezoelectric ceramic layer 22 can be improved.

[0027] As specific examples of the second crystal phase, the following various spinel compounds can be used. Examples of spinel compounds containing Li LiAlTiO4,LiCrTiO4,LiFeTiO4,LiGaTiO4,LiMnTiO4,LiYTiO4,LiScTiO4,LiCo 0.5Ti 1.5 O4, LiMg 0.5 Ti 1.5 O4, LiMn 0.5 Ti 1.5 O4,LiZn 0.5 Ti 1.5 O4,Li 1.33 (Zr,Ti) 1.67 O4 Examples of spinel compounds containing Co Co2TiO4,CoZnTiO4,CoMgTiO4,CoNiTiO4,CoFeTiO4,CoMnTiO4 Examples of spinel compounds containing Zn Zn2TiO4,ZnMgTiO4,ZnNiTiO4,ZnFeTiO4,ZnMnTiO4 Examples of spinel compounds containing Mg Mg2TiO4,MgNiTiO4,MgFeTiO4,MgMnTiO4 Examples of spinel compounds containing Ni Ni2TiO4,NiFeTiO4,NiMnTiO4,Ni 1.5 FeTi 0.5 O4,Ni2(Ti,Zr)O4 Examples of spinel compounds containing Fe Fe2TiO4,FeMnTiO4,Mn 1.5 FeTi 0.5 O4 Examples of spinel compounds containing Mn Mn2TiO4

[0028] A2B6O 13 In the compound, the element A preferably contains at least one of Li (lithium), Na (sodium), and K (potassium), and the element B preferably contains at least one of Co (cobalt), Fe (iron), Mg (magnesium), Ni (nickel), Zr (zirconium), Mn (manganese), Al (aluminum), Nb (niobium), Ta (tantalum), W (tungsten), and Ti (titanium).

[0029] A3B5O 15As the compound, a compound in which the element A (monovalent or divalent metal) is at least one of Ba, Ca, Sr, Na, K, and Li, and the element B (divalent or pentavalent metal) is at least one of Nb, Ta, Ti, Mn, Fe, Ni, Co, Zn, and Zr can be used. Specifically, for example, (Ba,Na,K)3(Nb,Fe)5O 15 ,(Ba,Na,K)3(Nb,Ni,Fe)5O 15 ,(Ba,Na,K)3(Nb,Co,Ni)5O 15 ,(Ba,Na,K)3(Nb,Zn)5O 15 ,(Ba,Na,K)3(Nb,Mn)5O 15 ,(Ba,Na,K)3(Nb,Fe,Zn,Co)5O 15 etc. can be used.

[0030] The subphase may contain a metal oxide other than the above metal oxides (A) to (E). When the subphase contains a metal oxide other than the above metal oxides (A) to (E), the volume ratio of the above metal oxides (A) to (E) to the total volume of the subphase (100%) is preferably greater than 50%, more preferably 70% or more, and even more preferably 80% or more.

[0031] (3) Silver (Ag) content in the piezoelectric ceramic layer 22 The silver (Ag) content in the piezoelectric ceramic layer 22 can be obtained by, for example, SEM-EDX elemental analysis. For example, SEM-EDX elemental analysis is performed on a cross section of the piezoelectric ceramic layer 22 sandwiched between a pair of internal electrodes 24 at the center position in the thickness direction (stacking direction).

[0032] The silver (Ag) content in the piezoelectric ceramic layer 22 obtained by SEM-EDX elemental analysis is 0.67 wt % or more, preferably 1.65 wt % or more, and more preferably 1.93 wt % or more, from the viewpoint of reducing the particle size of the first crystal phase in the piezoelectric ceramic layer 22, where the total content of sodium (Na), potassium (K), niobium (Nb), palladium (Pd), and silver (Ag) in the piezoelectric ceramic layer 22 is taken as 100 wt %. The silver (Ag) content is 2.02 wt % or less, preferably 2.00 wt % or less, and more preferably 1.95 wt % or less, from the viewpoint of suppressing a decrease in the insulating properties of the piezoelectric ceramic layer 22. From these viewpoints, the silver (Ag) content is 0.67 wt % or more and 2.02 wt % or less, preferably 1.65 wt % or more and 2.00 wt % or less, and more preferably 1.93 wt % or more and 1.95 wt % or less.

[0033] (4) Average particle size of the crystal grains of the first crystal phase The average particle size of the crystal grains of the first crystal phase (also simply referred to as the average particle size of the first crystal phase) can be determined as follows. First, the particles of the first crystal phase are observed in the cross section of the piezoelectric ceramic layer 22 using an SEM. For example, the piezoelectric ceramic layer 22 sandwiched between a pair of internal electrodes 24 is observed at a viewing angle of 50 μm × 70 μm in a cross section including the center position in the thickness direction (stacking direction). For the observed image, the projected outline of the particles of the first crystal phase (see FIG. 3) is measured using image analysis software (PhotoRuler). The maximum distance L between two points on this projected outline is defined as the particle size. The particle sizes of all particles in the image are calculated, and the average value of the particle sizes of all particles is defined as the average particle size of the first crystal phase.

[0034] The average particle size of the first crystal phase (a crystal phase made of alkali niobate perovskite oxide) in the piezoelectric ceramic layer 22 is preferably 2.25 μm or less, more preferably 2.20 μm or less, and even more preferably 1.80 μm or less, from the viewpoint of improving the strength of the laminate 20 (specifically, the piezoelectric ceramic layer 22). From the viewpoint of piezoelectric characteristics (displacement), the average particle size of the first crystal phase is preferably 1.30 μm or more, more preferably 1.50 μm or more, and even more preferably 1.70 μm or more. From these viewpoints, the average particle size of the first crystal phase is preferably 1.30 μm or more to 2.25 μm or less, more preferably 1.50 μm or more to 2.20 μm or less, and even more preferably 1.70 μm or more to 1.80 μm or less.

[0035] (4) Specific gravity of the piezoelectric ceramic layer 22 The specific gravity of the piezoelectric ceramic layer 22 is, for example, the specific gravity near the center position in the thickness direction (stacking direction) of the piezoelectric ceramic layer 22 sandwiched between a pair of internal electrodes 24. The measurement method can be performed by polishing both the top and bottom surfaces to expose the ceramic, and then measuring using the Archimedes method.

[0036] From the viewpoint of suppressing abnormal grain growth, the specific gravity of the piezoelectric ceramic layer 22 is preferably 4.30 or more, more preferably 4.35 or more, and even more preferably 4.40 or more. There is no particular upper limit to the specific gravity of the piezoelectric ceramic layer 22.

[0037] (5) Strength of the laminate 20 (flexural strength) The strength (flexural strength) of the laminate 20 can be measured as follows. The laminate 20 used for strength measurement has, for example, a rectangular parallelepiped shape. The size of the laminate 20 is, for example, 8 mm in width along the electrode lead-out direction (dimension in the X direction in FIG. 1), 3 mm in width along the direction perpendicular to the electrode lead-out direction (dimension in the Y direction in FIG. 1), and 50 mm in stack height (dimension in the Z direction in FIG. 1). Strength measurement can be performed in accordance with JIS R 1601, where the three-point bending strength of each sample can be determined under the condition of an external support distance (span) of 30 mm.

[0038] The strength (flexural strength) of the laminate 20 is preferably 2.5 MPa or more, more preferably 4.0 MPa or more, and even more preferably 5.0 MPa or more.

[0039] 2. Manufacturing method of piezoelectric ceramic laminate 10 4 is a flowchart showing a method for manufacturing the piezoelectric ceramic laminate 10 of the present disclosure. In step T110, first, as raw materials for the first crystal phase (main phase), necessary materials are selected from K2CO3 powder, Na2CO3 powder, Li2CO3 powder, CaCO3 powder, SrCO3 powder, BaCO3 powder, Nb2O5 powder, Ta2O5 powder, TiO2 powder, ZrO2 powder, HfO2 powder, MgO powder, Fe2O3 powder, CoO powder, ZnO powder, etc., and weighed out according to the values ​​of the coefficients a, b, c, d, e, f, and g in the composition formula (1) of the main phase. As raw materials for the second crystal phase (subphase), necessary materials are selected from TiO2 powder, Li2CO3 powder, Na2CO3 powder, K2CO3 powder, Co3O4 powder, Fe2O3 powder, MgO powder, NiO powder, ZrO2 powder, MnO2 powder, Al2O3 powder, Nb2O5 powder, Ta2O5 powder, WO3 powder, etc., and weighed out according to the value of coefficient x3 in the composition formula (3) of the subphase. The weighed raw materials for the main phase and subphase are mixed to obtain a mixed powder.

[0040] In step T120, the mixed powder obtained in step T110 is calcined in an air atmosphere at 600°C to 1200°C for 1 hour to 10 hours to produce a calcined powder. The relationship between the subphase ratio (wt%) during mixing in step T110 and the subphase ratio (volume%) in the finally obtained piezoelectric ceramic layer 22 can be empirically determined in advance.

[0041] In step T130, the calcined powder obtained in step T120, a binder, and a solvent are wet mixed and formed into a green sheet of a predetermined thickness by a casting sheet molding.

[0042] In step T140, the green sheet obtained in step T130 is punched out to a size of 150 mm square, and internal electrodes are printed using silver (Ag) paste or silver (Ag) / palladium (Pd) paste to obtain a driving layer. Here, some of the punched green sheets without internal electrodes printed on them (referred to as non-driving layers) are also prepared.

[0043] In step T150, the driving layers and non-driving layers obtained in step T140 are stacked in a predetermined number and order, and pressure-laminated at 40°C to 80°C and a pressure of 5MPa to 100MPa. The stack is then cut into small pieces.

[0044] In step T160, the small pieces obtained in step T150 are degreased in an air atmosphere at a holding temperature of 500°C to 800°C for a holding time of 2 hours to 100 hours.

[0045] In step T170, the degreased small pieces obtained in step T160 are fired in an air atmosphere at 900°C to 1400°C for 1 hour to 100 hours to obtain a fired body.

[0046] In step T180, the four sides of the rectangular sintered body obtained in step T170 are diced to reduce its dimensions and expose the internal electrodes. The sintered body is then processed to the required dimensional accuracy. For example, the top and bottom surfaces of the sintered body (both end surfaces in the stacking direction) are polished to adjust the thickness and achieve parallelism.

[0047] In step T190, a pair of side electrodes is printed on the fired body and baked at 600° C. to 800° C. In step T200, the fired body with the pair of side electrodes attached is subjected to a polarization treatment.

[0048] The above-described manufacturing method is an example, and various other steps and processing conditions can be used to manufacture the piezoelectric ceramic laminate 10.

[0049] 3. Application Examples of the Piezoelectric Ceramic Laminate 10 The piezoelectric ceramic laminate 10 can be widely used for actuators, oscillations, vibration detection, pressure detection, piezoelectric devices, etc. For example, it can be used in various devices such as actuators for mass flow controllers, piezoelectric motors, piezoelectric filters, piezoelectric transformers, piezoelectric ultrasonic transducers, piezoelectric gyro sensors, and knock sensors.

[0050] 4. Effects of this embodiment Piezoelectric ceramic layers manufactured using KNN materials (materials composed of alkali niobate perovskite oxides) exhibited poor sintering properties and a relatively low specific gravity. As a result, abnormal grain growth was likely to occur in parts of the piezoelectric ceramic layer. Furthermore, in such piezoelectric ceramic layers, the average grain size of the primary crystal phase was relatively large, resulting in relatively low strength. As a result, such piezoelectric ceramic layers were prone to chipping during dicing and had poor handling properties.

[0051] Therefore, in this embodiment, the silver (Ag) content in the piezoelectric ceramic layer 22 obtained by SEM-EDX elemental analysis is set to 0.67% or more and 2.02% or less by weight. With this configuration, silver (Ag) functions as a sintering aid, allowing the specific gravity of the piezoelectric ceramic layer 22 to be relatively large. This also allows the average grain size of the first crystal phase in the piezoelectric ceramic layer to be small, improving strength. Furthermore, since the silver (Ag) content does not become extremely small, migration of silver (Ag) during operation of the piezoelectric ceramic laminate 10 can be suppressed, thereby suppressing deterioration in insulation and current flow. [Example]

[0052] The present invention will be explained in more detail below with reference to examples. 1. Fabrication of Piezoelectric Ceramic Laminates The piezoelectric ceramic laminates of Comparative Example 1 and Examples 1-4 were fabricated using a method similar to the "method for manufacturing the piezoelectric ceramic laminate 10" of the above embodiment.

[0053] In step T110, first, K2CO3 powder, Na2CO3 powder, Li2CO3 powder, Nb2O5 powder, and CaCO3 powder were weighed as the raw material (KNLNC material) for the first crystal phase (main phase). The raw materials were weighed according to the values ​​of the coefficients a, b, c, d, e, f, and g in the composition formula (1) above to obtain an alkali niobate perovskite oxide of the desired composition. Nb2O5 powder, TiO2 powder, and K2CO3 powder were weighed as the raw material (NTK material) for the second crystal phase (subphase). The raw materials were weighed according to the value of the coefficient x3 in the composition formula (3) above to obtain a second crystal phase (subphase) of the desired composition. The weighed raw materials for the main phase and subphase were mixed to obtain a mixed powder.

[0054] In step T120, the mixed powder obtained in step T110 was calcined in an air atmosphere to generate a calcined powder. In Examples 1-4 and Comparative Example 1, the calcination was carried out at 900° C. for 10 hours.

[0055] In step T130, the calcined powder obtained in step T120, a binder, and a solvent were wet mixed and formed into a green sheet of a predetermined thickness by a casting sheet molding.

[0056] In step T140, the green sheet obtained in step T130 was punched out to a size of 150 mm square, and internal electrodes were attached to obtain a driving layer. In comparative example 1, platinum (Pt) electrodes were used. In examples 1-4, internal electrodes were printed using silver (Ag) / palladium (Pd) paste to obtain a driving layer. Here, some of the punched green sheets without internal electrodes printed on them (referred to as non-driving layers) were also prepared.

[0057] In step T150, the driving layers and non-driving layers obtained in step T140 were stacked in a predetermined number and order, and pressure was applied to compress and laminate them. In Examples 1-4 and Comparative Example 1, a pressure of 10 MPa to 50 MPa was applied at 40°C to 60°C. The laminate was then cut into small pieces.

[0058] In step T160, the small pieces obtained in step T150 were degreased by holding them at a high temperature in an air atmosphere. In Examples 1-4 and Comparative Example 1, the temperature was held at 500° C. for 4 hours.

[0059] In step T170, the degreased pieces obtained in step T160 were fired in an air atmosphere to obtain fired bodies. In Comparative Example 1, firing was performed at 1100°C for 10 hours. In Example 1, firing was performed at 1130°C for 10 hours. In Example 2, firing was performed at 1130°C for 30 hours. In Example 3, firing was performed at 1130°C for 50 hours. In Example 4, firing was performed at 1130°C for 70 hours.

[0060] In step T180, the four sides of the rectangular parallelepiped sintered body obtained in step T170 were diced to reduce the dimensions and expose the internal electrodes.Then, the top and bottom surfaces of the sintered body (both end surfaces in the stacking direction) were polished to adjust the thickness and achieve parallelism.

[0061] In step T190, a pair of side electrodes was printed on the fired body and baked. In Examples 1-4 and Comparative Example 1, the baking was performed at 600°C.

[0062] In step T200, the fired body with the pair of side electrodes attached thereto was subjected to a polarization treatment. In this manner, a piezoelectric ceramic laminate was obtained.

[0063] 2. Evaluation Method (1) Composition evaluation The piezoelectric ceramic layer was subjected to elemental analysis using a SEM-EDX (JSM-6390LA manufactured by JOEL). Elemental analysis by SEM-EDX was performed on a cross section at the center position in the thickness direction (stacking direction) of the piezoelectric ceramic layer sandwiched between a pair of internal electrodes. The analysis results are shown in Table 1.

[0064] [Table 1]

[0065] In Table 1, the values ​​in the "Elemental Analysis Results" column for each element symbol indicate the percentage (unit: atm%) when the total of the detected elements Na, K, Nb, Pd, and Ag is taken as 100 atm%. In Table 1, the values ​​in the "Ag Percentage (wt.%)" column indicate the silver (Ag) content (percentage (wt.%)) obtained by SEM-EDX elemental analysis when the total of the detected elements Na, K, Nb, Pd, and Ag in the piezoelectric ceramic layer is taken as 100 wt.%.

[0066] (2) Evaluation of the average particle size of the first crystal phase The average particle size of the crystal grains of the first crystal phase was determined using the same method as in the above embodiment. First, the particles of the first crystal phase were observed in a cross section of the piezoelectric ceramic layer using an SEM. The piezoelectric ceramic layer sandwiched between a pair of internal electrodes was observed at a 50 μm × 70 μm viewing angle in a cross section including the center position in the thickness direction (stacking direction). For the observed image, image analysis software (PhotoRuler) was used to derive the projected contour line of the first crystal phase particles (see FIG. 3). The maximum distance L between two points on this projected contour line was defined as the particle size. The particle sizes of all particles in the image were calculated, and the average value of the particle sizes of all particles was defined as the average particle size of the crystal grains of the first crystal phase. The measurement results are shown in Table 1. FIG. 5 is a cross-sectional SEM image of the piezoelectric ceramic layer of Example 1. FIG. 6 is a cross-sectional SEM image of the piezoelectric ceramic layer of Example 4.

[0067] (3) Evaluation of the specific gravity of the piezoelectric ceramic layer The specific gravity of the piezoelectric ceramic layer was measured by using the Archimedes method at the center position in the thickness direction (stacking direction) of the piezoelectric ceramic layer sandwiched between a pair of internal electrodes. The measurement results are shown in Table 1.

[0068] (4) Strength of laminate (flexural strength) The strength (flexural strength) of the laminate was measured in the same manner as in the embodiment. The laminate used for strength measurement had a rectangular parallelepiped shape. The size of the laminate was, for example, 8 mm in width along the electrode lead-out direction (dimension in the X direction in FIG. 1), 3 mm in width along the direction perpendicular to the electrode lead-out direction (dimension in the Y direction in FIG. 1), and 50 mm in stack height (dimension in the Z direction in FIG. 1). Strength measurement was performed in accordance with JIS R 1601, where the three-point bending strength of each sample was determined under the condition of an external support distance (span) of 30 mm. The measurement results are shown in Table 1.

[0069] 3.Results The specific gravity of the piezoelectric ceramic layer in Examples 1-4 was 4.48-4.54. In contrast, the specific gravity of the piezoelectric ceramic layer in Comparative Example 1 was 4.21. Examples 1-4 satisfy the following requirement (a). Comparative Example 1 does not satisfy the following requirement (a). Requirement (a): The internal electrodes contain silver (Ag). In Example 1-4, it is believed that by including silver (Ag) in the internal electrodes, silver (Ag) diffused from the internal electrodes into the piezoelectric ceramic layer, thereby increasing the specific gravity of the piezoelectric ceramic layer.

[0070] The average particle size of the first crystal phase in the piezoelectric ceramic layer of Example 1-4 was 1.30-2.87. The flexural strength of the piezoelectric ceramic layer of Example 1-4 was 2.8-10.1, which was higher than the flexural strength of the piezoelectric ceramic layer of Comparative Example 1. Example 1-4 satisfies the following requirement (b). Requirement (b): The silver (Ag) content in the piezoelectric ceramic layer obtained by elemental analysis using SEM-EDX is 0.67% by weight or more and 2.02% by weight or less. It is believed that in Example 1-4, the average particle size of the first crystal phase could be made relatively large by satisfying the above requirement (b), and this allowed the bending strength of the laminate to be made relatively high.

[0071] The flexural strength of the piezoelectric ceramic layer in Example 1-3 was 5.6-10.1. The flexural strength of the piezoelectric ceramic layer in Example 4 was 2.8. Example 1-3 satisfies the following requirement (c). Example 1-4 does not satisfy the following requirement (c). Requirement (c): The silver (Ag) content in the piezoelectric ceramic layer obtained by elemental analysis using SEM-EDX is 1.65% by weight or more and 2.02% by weight or less. In Example 1-3, the average particle size of the first crystal phase was 1.30-2.25 by satisfying the above requirement (c), which was smaller than the average particle size of the first crystal phase of 2.87 in Example 4. It is believed that by making the average particle size of the first crystal phase smaller in this way, the bending strength of the laminate was further increased. 4. Effects of the Example According to the above examples, it is believed that silver (Ag) functions as a sintering aid in the piezoelectric ceramic layer, making it possible to relatively increase the specific gravity of the piezoelectric ceramic layer, and also to reduce the grain size in the piezoelectric ceramic layer, thereby improving its strength.

[0072] The present disclosure is not limited to the above-described embodiments, and various modifications and variations are possible. [Explanation of symbols]

[0073] 10: Piezoelectric ceramic laminate 20: Laminate 22: Piezoelectric ceramic layer 24: Internal electrode 24A: Extraction electrode 30: Side electrode 41: Driving Layer 43: Non-driven layer

Claims

1. A piezoelectric ceramic laminate in which piezoelectric ceramic layers and internal electrodes are alternately stacked, the piezoelectric ceramic layer contains a crystalline phase made of an alkali niobate perovskite oxide having piezoelectric properties; the internal electrodes contain silver (Ag); The silver (Ag) content in the piezoelectric ceramic layer obtained by elemental analysis using SEM-EDX is 0.67% by weight or more and 2.02% by weight or less. Piezoelectric ceramic laminate.

2. The silver (Ag) content in the piezoelectric ceramic layer obtained by elemental analysis using SEM-EDX is 1.65% by weight or more and 2.02% by weight or less. The piezoelectric ceramic laminate according to claim 1 .

3. The average particle size of the crystal grains of the crystalline phase is 2.25 μm or less.

3. The piezoelectric ceramic laminate according to claim 1 or 2.

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