Piezoelectric element, piezoelectric ceramic composition, method for manufacturing piezoelectric element, and method for manufacturing piezoelectric ceramic composition

Abstract

A piezoelectric element (for example, a piezoelectric actuator (10)) is provided with a piezoelectric ceramic layer (3) comprising a ceramic sintered body in which a main phase containing K, Na, Nb, and Mn and a second phase containing Mn and Nb are present.

Description

Technical Field

[0001] The present invention relates to a piezoelectric element, a piezoelectric ceramic composition, a method for producing a piezoelectric element, and a method for producing a piezoelectric ceramic composition. Background Art

[0002] Conventionally, as piezoelectric elements using piezoelectric materials, piezoelectric ceramic electronic components such as ultrasonic sensors, piezoelectric buzzers, and piezoelectric actuators are well known.

[0003] Lead zirconate titanate (PZT) compounds represented by the general formula Pb(Zr, Ti)O3 have been used as piezoelectric materials so far. In recent years, potassium sodium niobate (KNN) compounds represented by the general formula (K, Na)NbO3 have attracted much attention as non-lead piezoelectric materials.

[0004] Patent document 1 discloses a piezoelectric ceramic composed of a polycrystal with an alkali-containing niobate perovskite structure as the main phase, in which nickel and manganese elements are present on the grain boundaries of the polycrystal. Relative to 100 moles of the above-mentioned main phase, the content of manganese element is 0.1 mole to 2.0 moles, the content of nickel element is 0.1 mole to 2.0 moles, the content of lithium element is 0.2 mole to 3.0 moles, the content of silicon element is 0.2 mole to 3.0 moles, the content of strontium element is less than 2.0 moles, and the content of zirconium element is less than 2.0 moles.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent No. 6039715 Summary of the invention

[0008] According to Patent Document 1, the nickel-containing phase and the manganese-containing phase are intentionally locally enriched at the grain boundaries of the main phase inside the piezoelectric ceramic, thereby achieving improvement in insulation performance while maintaining the piezoelectric characteristics of the piezoelectric element.

[0009] Patent document 1 describes that in order to manufacture a piezoelectric element containing piezoelectric ceramics, a mixed powder of raw material powder as a main phase is pre-fired and then mixed with MnO powder and NiO powder, that is, the pre-fired powder of the main phase and the MnO powder and NiO powder exist as independent particles, and then fired in an air atmosphere.

[0010] In the examples of Patent Document 1, the insulation performance is evaluated by the resistivity when a high DC electric field of 2 kV / mm is applied between the external electrodes of the piezoelectric element. However, it is found that in the piezoelectric ceramics described in Patent Document 1, when a higher electric field exceeding 2 kV / mm is applied, the resistivity decreases in a high temperature environment compared to a room temperature environment, making it difficult to achieve both insulation performance and piezoelectric characteristics.

[0011] The present invention is made to solve the above-mentioned problems, and its purpose is to provide a piezoelectric element in which the reduction of insulation performance when a high electric field is applied in a high temperature environment is suppressed. In addition, the present invention also aims to provide a piezoelectric ceramic composition in which the reduction of insulation performance when a high electric field is applied in a high temperature environment is suppressed. In addition, the present invention aims to provide a method for manufacturing the above-mentioned piezoelectric element and a method for manufacturing the above-mentioned piezoelectric ceramic composition.

[0012] The piezoelectric element of the present invention includes a piezoelectric ceramic layer composed of a ceramic sintered body having a main phase containing K, Na, Nb, and Mn and a secondary phase containing Mn and Nb.

[0013] The piezoelectric ceramic composition of the present invention is composed of a ceramic sintered body having a main phase containing K, Na, Nb, and Mn and a secondary phase containing Mn and Nb.

[0014] The method for manufacturing a piezoelectric element of the present invention comprises: a step of preparing a calcined product by mixing a K compound containing K, a Na compound containing Na, and a Nb compound containing Nb and calcining the mixture; a step of preparing a ceramic green sheet containing the calcined product and a Mn compound containing Mn; and a step of sintering the ceramic green sheet in a reducing atmosphere.

[0015] The method for producing a piezoelectric ceramic composition of the present invention comprises the following steps: a step of preparing a calcined product by mixing and calcining a K compound containing K, a Na compound containing Na, and a Nb compound containing Nb, a step of preparing a molded body containing a Mn compound containing Mn and the calcined product, and a step of calcining the molded body in a reducing atmosphere.

[0016] According to the present invention, a piezoelectric element can be provided in which the reduction of insulation performance when a high electric field is applied in a high temperature environment is suppressed. Furthermore, according to the present invention, a piezoelectric ceramic composition can be provided in which the reduction of insulation performance when a high electric field is applied in a high temperature environment is suppressed. Furthermore, according to the present invention, a method for manufacturing the above-mentioned piezoelectric element and a method for manufacturing the above-mentioned piezoelectric ceramic composition can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a cross-sectional view schematically showing an example of a stacked piezoelectric element as one embodiment of the piezoelectric element of the present invention.

[0018] Figure 2 This is a perspective view schematically showing an example of a ceramic green sheet obtained in the process of manufacturing a piezoelectric actuator.

[0019] Figure 3This is a perspective view schematically showing an example of a piezoelectric actuator on which external electrodes are formed.

[0020] Figure 4 This is a cross-sectional view schematically showing an example of a one-piece piezoelectric element as another embodiment of the piezoelectric element of the present invention.

[0021] Figure 5 This is an example of a TEM image of a ceramic sintered body containing a main phase and a secondary phase.

[0022] Figure 6 is with Figure 5 Mapping image of the Mn element at the same position.

[0023] Figure 7 This is an example of an XRD pattern of a ceramic sintered body containing a main phase and a secondary phase.

[0024] Figure 8 This is an example of an XRD pattern of a ceramic sintered body obtained by firing a calcined product containing a main phase of a KNN-based compound to which Mn is added in a reducing atmosphere in order to produce a monolithic piezoelectric element.

[0025] Fig. 9 This is an example of an XRD pattern of a ceramic sintered body obtained by firing a calcined product containing a main phase of a KNN-based compound to which Mn is added in a reducing atmosphere in order to produce a stacked piezoelectric element.

[0026] Fig.10 This is an example of an XRD pattern of a ceramic sintered body obtained by firing a calcined product containing a main phase of a KNN-based compound to which Mn is added in an air atmosphere in order to produce a monolithic piezoelectric element.

[0027] Fig.11 This is an XRD pattern (2θ=33° to 35°) when the amount of Li added was changed in the stacked piezoelectric element.

[0028] Fig.12 This is an XRD pattern (2θ=41° to 45°) when the amount of Li added is changed in the stacked piezoelectric element. DETAILED DESCRIPTION

[0029] The piezoelectric element of the present invention is described below. It should be noted that the present invention is not limited to the following embodiments and can be appropriately changed within the scope of the gist of the present invention. In addition, a combination of the preferred configurations described in a plurality of the following embodiments also belongs to the present invention.

[0030] The drawings shown below are schematic diagrams, and their dimensions, aspect ratios, and other aspects may differ from those of actual products.

[0031] Figure 1 This is a cross-sectional view schematically showing an example of a stacked piezoelectric element as one embodiment of the piezoelectric element of the present invention.

[0032] Figure 1 The piezoelectric actuator 10 shown is an example of a stacked piezoelectric element and includes piezoelectric ceramic layers 3 (3a to 3h) and internal electrode layers 4 (4a to 4g) provided on at least one main surface of the piezoelectric ceramic layers 3 and containing Ni as a main component (for example, 30 wt % or more).

[0033] like Figure 1 As shown, the piezoelectric actuator 10 preferably further includes external electrodes 2 ( 2 a , 2 b ) provided on both ends of the piezoelectric ceramic body 1 including the piezoelectric ceramic layers 3 and the internal electrode layers 4 alternately. Figure 1 Although not shown, external electrodes formed by sputtering or the like may be further provided on the surface and the back of the piezoelectric ceramic body 1. Examples of conductive materials constituting these external electrodes include NiCr, NiCu, Ag, Au, Pt, Ni, Cu, Sn, and the like.

[0034] In the piezoelectric actuator 10, one end of the internal electrode layers 4a, 4c, 4e, 4g is electrically connected to one external electrode 2a, and one end of the internal electrode layers 4b, 4d, 4f is electrically connected to the other external electrode 2b. In addition, when a voltage is applied between the external electrode 2a and the external electrode 2b, the piezoelectric actuator 10 is displaced in any direction due to the piezoelectric effect. For example, if it is a piezoelectric longitudinal effect, it will be displaced in the longitudinal direction (the stacking direction indicated by the arrow X), and if it is a piezoelectric transverse effect, it will be displaced in the transverse direction (a direction perpendicular to the stacking direction).

[0035] The piezoelectric ceramic layer 3 is composed of a ceramic sintered body having a main phase containing K, Na, Nb and Mn and a second phase containing Mn and Nb. Preferably, the second phase containing Mn and Ni also exists in the ceramic sintered body constituting the piezoelectric ceramic layer 3. Details of each phase will be described later.

[0036] The piezoelectric actuator 10 is preferably manufactured by the following method. Such a method for manufacturing a piezoelectric element is also one of the present invention.

[0037] First, as ceramic raw materials, K compounds containing K, Na compounds containing Na, and Nb compounds containing Nb are prepared respectively. Li compounds containing Li are prepared as needed. The form of the compound of the ceramic raw material is not particularly limited, and oxides, carbonates, bicarbonates, hydroxides, etc. can be cited. It should be noted that when adding divalent elements such as Ba, tetravalent elements such as Zr, and rare earth elements such as La, each element compound is prepared.

[0038] Next, a predetermined amount of the ceramic raw material is weighed and placed in a pulverizer such as a ball mill or a pot mill having a pulverizing medium such as PSZ (partially stabilized zirconia) balls, and is fully wet-pulverized in a solvent such as ethanol to obtain a mixture.

[0039] It should be noted that, in the process of preparing the mixture of ceramic raw materials, it is preferred not to add a Mn compound containing Mn.

[0040] The obtained mixture is dried and then pre-calcined at a predetermined temperature (eg, 850° C. to 1000° C.) to synthesize a potassium sodium niobate (KNN)-based compound, and then crushed to obtain a pre-calcined product.

[0041] A Mn compound such as MnCO3 is added to the obtained calcined product. Then, an organic binder and a dispersant are added, and wet mixing is performed in a ball mill using pure water or an organic solvent (such as ethanol) as a solvent to obtain a ceramic slurry. Then, a shaping process is performed using a scraper method or the like to produce a ceramic green sheet.

[0042] Next, a conductive paste for internal electrode layers containing Ni as a main component was screen-printed on the ceramic green sheet to form a conductive layer in a predetermined shape.

[0043] Figure 2 This is a perspective view schematically showing an example of a ceramic green sheet obtained in the process of manufacturing a piezoelectric actuator.

[0044] like Figure 2 As shown, after ceramic green sheets 5 (5a to 5g) each having conductive layers 6 (6a to 6g) are stacked, ceramic green sheets 7a not having conductive layers 6 are stacked and pressed. Thus, a ceramic stacked body in which ceramic green sheets 5 and conductive layers 6 are alternately stacked is produced.

[0045] The obtained ceramic laminate is cut into specified sizes, placed on a firing fixture such as an alumina saggar, and subjected to a binder removal treatment at a specified temperature (e.g., 250°C to 500°C). It is then fired at a specified temperature (e.g., 1000°C to 1160°C) in a reducing atmosphere to form a piezoelectric ceramic body 1 (ceramic sintered body) in which an internal electrode layer 4 is embedded.

[0046] When the conductive layer 6 mainly composed of Ni and the ceramic green sheet 5 mainly composed of the KNN compound are co-fired, it is necessary to perform the firing in a reducing atmosphere in order to prevent oxidation of Ni. It should be noted that the oxygen partial pressure of the reducing atmosphere is preferably the equilibrium oxygen partial pressure at which Ni and NiO are in equilibrium or a value lower than the equilibrium oxygen partial pressure so that Ni is not oxidized.

[0047] Next, a conductive paste for external electrodes made of Ag or the like is applied to the surface of the piezoelectric ceramic body to form external electrodes.

[0048] Figure 3 This is a perspective view schematically showing an example of a piezoelectric actuator on which external electrodes are formed.

[0049] like Figure 3 As shown, external electrodes 2a and 2b are formed at both ends of the piezoelectric ceramic body 1 by a method such as sputtering. It should be noted that the external electrodes 2a and 2b only need to have good adhesion to the piezoelectric ceramic body 1, and can be formed by a thin film forming method such as vacuum evaporation, or by a method such as baking a conductive paste.

[0050] Then, a predetermined polarization process is performed to manufacture the piezoelectric actuator 10 .

[0051] Figure 4 This is a cross-sectional view schematically showing an example of a one-piece piezoelectric element as another embodiment of the piezoelectric element of the present invention.

[0052] Figure 4 The piezoelectric actuator 20 shown is an example of a monolithic piezoelectric element. The piezoelectric actuator 20 includes a piezoelectric ceramic layer 13 .

[0053] like Figure 4 As shown, the piezoelectric actuator 20 includes external electrodes 12a and 12b provided on the front and back surfaces of a piezoelectric ceramic body 11 including a piezoelectric ceramic layer 13. Examples of conductive materials constituting these external electrodes include NiCr, NiCu, Ag, Au, Pt, Ni, Cu, and Sn.

[0054] When a voltage is applied between the external electrode 12a and the external electrode 12b, the piezoelectric actuator 20 is displaced in any direction due to the piezoelectric effect. For example, if it is the piezoelectric longitudinal effect, it is displaced in the longitudinal direction (the direction indicated by the arrow Y), and if it is the piezoelectric transverse effect, it is displaced in the transverse direction (the direction perpendicular to the direction indicated by the arrow Y).

[0055] The piezoelectric ceramic layer 13 is composed of a ceramic sintered body having a main phase containing K, Na, Nb and Mn and a second phase containing Mn and Nb. The second phase containing Mn and Ni may or may not exist in the ceramic sintered body constituting the piezoelectric ceramic layer 13. The details of each phase will be described later.

[0056] The piezoelectric actuator 20 can be manufactured, for example, by using a layer process and a press process to form a molded body having a predetermined component composition, and then applying a conductive paste for external electrodes containing Cu, Ni, Pt, etc. as a main component to both surfaces of the molded body, and co-firing the paste in a reducing atmosphere. It should be noted that the external electrodes can be formed by a method such as a sputtering method.

[0057] In the above-mentioned embodiments, stacked-type and single-piece piezoelectric elements are exemplified, but the present invention is applicable to various piezoelectric elements.

[0058] In the piezoelectric element of the present invention, the piezoelectric ceramic layer is composed of a ceramic sintered body having a main phase containing K, Na, Nb and Mn and a second phase containing Mn and Nb (hereinafter also referred to as the first second phase). It should be noted that the piezoelectric ceramic composition composed of the ceramic sintered body described below is also one of the present invention.

[0059] The main phase contains a KNN compound. The KNN compound has a perovskite structure and is represented by the general formula (K, Na)NbO 3. The composition of the KNN compound is not particularly limited.

[0060] The main phase may contain elements other than K, Na, Nb and Mn. For example, Li may be contained in the main phase as an alkali metal element. In addition, the main phase may contain divalent elements such as Ba, Ca and Sr, tetravalent elements such as Zr, Sn and Hf, rare earth elements such as Sc, In, Yb, Y, Nd, Eu, Gd, Dy, Sm, Ho, Er, Tb, Lu, La and Pr, Ta, Sb, Ni, etc.

[0061] The first second phase may further contain elements other than Mn and Nb.

[0062] The composition of the ceramic sintered body can be determined by, for example, observation using a transmission electron microscope (TEM) and energy dispersive X-ray analysis (EDX) and element distribution analysis.

[0063] Figure 5 This is an example of a TEM image of a ceramic sintered body containing a main phase and a secondary phase. Figure 6 is with Figure 5 Mapping image of the Mn element at the same position.

[0064] exist Figure 6In the case of Mn, the region where the element exists is equivalent to the second phase. Figure 5 and Figure 6 As shown, the secondary phase is preferably dispersed in the primary phase.

[0065] Figure 5 Table 1 shows the compositions of the main phase and the secondary phase contained in the ceramic sintered body.

[0066] [Table 1]

[0067]

[0068] According to Table 1, the main elements constituting the main phase are K, Na and Nb, and the main elements constituting the secondary phase are Mn and Nb.

[0069] In addition, by performing crystal structure analysis using X-ray diffraction (XRD), the crystal structure contained in the ceramic sintered body can be analyzed.

[0070] Figure 7 This is an example of an XRD pattern of a ceramic sintered body containing a main phase and a secondary phase.

[0071] exist Figure 7 In addition to the peaks marked with ◆ from the main phase containing the KNN-based compound and the peaks marked with ■ from Ni, peaks marked with ● from the secondary phase containing Mn and Nb can also be confirmed. Figure 7 In the example shown, the second phase containing Mn and Nb has a crystal structure of the Mn4Nb2O9 type.

[0072] The above results show that Mn added after synthesis by pre-sintering the main phase containing the KNN-based compound releases Nb from the B site during firing. If Nb that enters the crystal during pre-sintering is released from the crystal in a state of being acquired in a second phase (heterophase) containing Mn during firing, Nb defects with acceptor functions are generated at the B site of the main phase. This Nb defect contributes to charge compensation of 2.5 moles of oxygen defects per 1 mole, which is related to improving insulation performance in high temperature environments. It should be noted that part of the Nb at the B site can also be replaced by elements such as Zr, in which case elements such as Zr can be acquired in a second phase (heterophase) containing Mn and released from the crystal.

[0073] In addition, K and Na (or Li) dissolved in the A site in the main phase crystal are taken into the second phase (heterophase) containing Mn and separated from the crystal, thereby forming K defects and Na defects (or Li defects) at the A site. Since these defects can obtain acceptor functions, they all contribute to charge compensation of oxygen defects and are related to improving insulation performance in high temperature environments.

[0074] Thus, in the present invention, by including the element contained in the main phase in the secondary phase, defects are formed in the main phase, thereby improving the insulation performance in a high temperature environment.

[0075] Figure 8 This is an example of an XRD pattern of a ceramic sintered body obtained by firing a calcined product containing a main phase of a KNN-based compound to which Mn is added in a reducing atmosphere in order to produce a monolithic piezoelectric element.

[0076] like Figure 8 As shown, the second phase containing Mn and Nb preferably has a peak in the range of 2θ=33° to 35° in the crystal structure analysis using X-ray diffraction. Figure 8 In the example shown, the second phase containing Mn and Nb has a crystal structure of the Mn4Nb2O9 type.

[0077] In the crystal structure analysis using X-ray diffraction, when the maximum peak intensity of the main phase is set to I0 and the maximum peak intensity in the range of 2θ=33°~35° of the second phase containing Mn and Nb is set to I1, the maximum peak intensity ratio represented by I1 / I0 is preferably greater than 0.019 and less than 0.070.

[0078] Fig. 9 This is an example of an XRD pattern of a ceramic sintered body obtained by firing a calcined product containing a main phase of a KNN-based compound to which Mn is added in a reducing atmosphere in order to produce a stacked piezoelectric element.

[0079] In a stacked piezoelectric element, an internal electrode layer containing Ni as a main component is provided on at least one main surface of a piezoelectric ceramic layer. Fig. 9 As shown, the second phase containing Mn and Nb preferably has a peak in the range of 2θ=33° to 35° in the crystal structure analysis using X-ray diffraction. Fig. 9 In the example shown, the second phase containing Mn and Nb has a ZnNb2Mn3O9 type crystal structure.

[0080] When the internal electrode layer containing Ni as a main component is provided on at least one main surface of the piezoelectric ceramic layer, it is preferred that a second phase containing Mn and Ni (hereinafter also referred to as a second second phase) further exists in the ceramic sintered body.

[0081] The second second phase may contain elements other than Mn and Ni.

[0082] like Fig. 9 As shown, the second phase containing Mn and Ni preferably has a peak in the range of 2θ=41° to 44° in the crystal structure analysis using X-ray diffraction. Fig. 9 In the example shown, the second phase containing Mn and Ni has Mn0.5 Ni 0.5 O (i.e. MnNiO2) type crystal structure.

[0083] In the crystal structure analysis using X-ray diffraction, when the maximum peak intensity of the main phase is set to I0 and the maximum peak intensity in the range of 2θ=41°~44° of the second phase containing Mn and Ni is set to I2, the maximum peak intensity ratio represented by I2 / I0 is preferably greater than 0 and less than 0.04.

[0084] like Figure 8 and Fig. 9 As shown, the ceramic sintered body preferably has no peak near 2θ=29° in crystal structure analysis using X-ray diffraction.

[0085] Fig.10 This is an example of an XRD pattern of a ceramic sintered body obtained by firing a calcined product containing a main phase of a KNN-based compound to which Mn is added in an air atmosphere in order to produce a monolithic piezoelectric element.

[0086] Firing in air Fig.10 In the example shown, the Figure 8 Unlike the example shown, in the crystal structure analysis using X-ray diffraction, it can be confirmed that a second phase having a peak in the range of 2θ = 33° to 35° is not formed. Instead, peaks of LiMn2O4 and ZrO2 can be confirmed. It should be noted that the peak near 2θ = 34° is the peak of ZrO2, which is different from the peak of the second phase containing Mn and Nb.

[0087] Fig.11 This is an XRD pattern (2θ=33° to 35°) when the amount of Li added was changed in the stacked piezoelectric element.

[0088] like Fig.11 As shown, within the range of 2θ=33° to 35°, a peak having a Mn4Nb2O9 type or ZnNb2Mn3O9 type crystal structure can be confirmed as a second phase containing Mn and Nb.

[0089] Fig.12 This is an XRD pattern (2θ=41° to 45°) when the amount of Li added is changed in the stacked piezoelectric element.

[0090] like Fig.12 As shown, in the range of 2θ=41° to 44°, a peak having a MnNiO2 type crystal structure can be confirmed as a second phase containing Mn and Ni.

[0091] The following contents are disclosed in this specification.

[0092] <1>

[0093] A piezoelectric element comprises a piezoelectric ceramic layer.

[0094] The piezoelectric ceramic layer is composed of a ceramic sintered body having a main phase containing K, Na, Nb, and Mn and a secondary phase containing Mn and Nb.

[0095] <2>

[0096] The piezoelectric element according to <1>, wherein the second phase containing Mn and Nb has a peak in the range of 2θ=33° to 35° in a crystal structure analysis using X-ray diffraction.

[0097] <3>

[0098] According to the piezoelectric element described in <2>, wherein, in the above-mentioned crystal structure analysis using X-ray diffraction, when the maximum peak intensity of the above-mentioned main phase is set to I0, and the maximum peak intensity in the range of 2θ=33°~35° of the above-mentioned second phase containing Mn and Nb is set to I1, the maximum peak intensity ratio represented by I1 / I0 is greater than 0.019 and less than 0.070.

[0099] <4>

[0100] The piezoelectric element according to any one of <1> to <3>, further comprising an internal electrode layer provided on at least one main surface of the piezoelectric ceramic layer and containing Ni as a main component.

[0101] <5>

[0102] The piezoelectric element according to <4>, wherein a second phase containing Mn and Ni further exists in the ceramic sintered body.

[0103] <6>

[0104] The piezoelectric element according to <5>, wherein the second phase containing Mn and Ni has a peak in the range of 2θ=41° to 44° in a crystal structure analysis using X-ray diffraction.

[0105] <7>

[0106] According to the piezoelectric element described in <6>, wherein, in the above-mentioned crystal structure analysis using X-ray diffraction, when the maximum peak intensity of the above-mentioned main phase is set to I0, and the maximum peak intensity in the range of 2θ=41°~44° of the above-mentioned second phase containing Mn and Ni is set to I2, the maximum peak intensity ratio represented by I2 / I0 is greater than 0 and less than 0.04.

[0107] <8>

[0108] A piezoelectric ceramic composition is composed of a ceramic sintered body having a main phase containing K, Na, Nb and Mn and a secondary phase containing Mn and Nb.

[0109] <9>

[0110] The piezoelectric ceramic composition according to <8>, wherein the second phase containing Mn and Nb has a peak in the range of 2θ=33° to 35° in a crystal structure analysis using X-ray diffraction.

[0111] <10>

[0112] According to the piezoelectric ceramic composition described in <9>, wherein, in the above-mentioned crystal structure analysis using X-ray diffraction, when the maximum peak intensity of the above-mentioned main phase is set to I0 and the maximum peak intensity in the range of 2θ=33°~35° of the above-mentioned second phase containing Mn and Nb is set to I1, the maximum peak intensity ratio represented by I1 / I0 is greater than 0.019 and less than 0.070.

[0113] <11>

[0114] The piezoelectric ceramic composition according to any one of <8> to <10>, wherein a second phase containing Mn and Ni is further present in the ceramic sintered body.

[0115] <12>

[0116] The piezoelectric ceramic composition according to <11>, wherein the second phase containing Mn and Ni has a peak in the range of 2θ=41° to 44° in a crystal structure analysis using X-ray diffraction.

[0117] <13>

[0118] According to the piezoelectric ceramic composition described in <12>, wherein, in the above-mentioned crystal structure analysis using X-ray diffraction, when the maximum peak intensity of the above-mentioned main phase is set to I0 and the maximum peak intensity in the range of 2θ=41°~44° of the above-mentioned second phase containing Mn and Ni is set to I2, the maximum peak intensity ratio represented by I2 / I0 is less than 0.04.

[0119] <14>

[0120] A method for manufacturing a piezoelectric element, comprising:

[0121] A process of preparing a calcined product by mixing a K compound containing K, a Na compound containing Na, and a Nb compound containing Nb and calcining the mixture.

[0122] a step of preparing a ceramic green sheet containing a Mn-containing Mn compound and the calcined product; and

[0123] A step of firing the ceramic green sheet in a reducing atmosphere.

[0124] <15>

[0125] The method for producing a piezoelectric element according to <14> further comprises, before the step of firing the ceramic green sheet, a step of forming a conductive layer on the ceramic green sheet using a conductive paste containing Ni as a main component.

[0126] <16>

[0127] The method for producing a piezoelectric element according to <15> further comprises, before the step of firing the ceramic green sheets, a step of stacking the ceramic green sheets on which the conductive layers are formed to produce a ceramic laminate.

[0128] <17>

[0129] A method for manufacturing a piezoelectric ceramic composition, comprising:

[0130] A process of preparing a calcined product by mixing a K compound containing K, a Na compound containing Na, and a Nb compound containing Nb and calcining the mixture.

[0131] a step of preparing a molded body containing a Mn-containing Mn compound and the calcined product, and

[0132] A step of firing the molded body in a reducing atmosphere.

[0133] Example

[0134] Hereinafter, examples which more specifically disclose the piezoelectric element of the present invention will be described, but it should be noted that the present invention is not limited to these examples.

[0135] [Example 1-1]

[0136] In Example 1-1, as shown in Table 2, multilayer piezoelectric elements having different Mn addition amounts were produced.

[0137] First, as ceramic raw materials, K2CO3, Na2CO3, Li2CO3, Nb2O3, and BaZrO3 are prepared. A predetermined amount of the above ceramic raw materials is weighed, and then the weighed material is put into a ball mill and fully wet-milled to obtain a mixture. After the obtained mixture is dried, it is pre-calcined and crushed to obtain a pre-calcined product.

[0138] Next, the calcined product and MnCO3 are prepared, a predetermined amount is weighed, and they are put into a ball mill together with an organic binder, a dispersant and a solvent (pure water or an organic solvent (ethanol, etc.)) and fully wet mixed. Then, a scraper method is used to implement molding processing to obtain a ceramic green sheet.

[0139] Next, a conductive paste for internal electrode layers containing Ni as a main component is used to form a conductive layer having a predetermined pattern on the ceramic green sheets by screen printing. After a predetermined number of ceramic green sheets with conductive layers formed thereon are stacked, ceramic green sheets without conductive layers formed thereon are stacked and pressed together. Thus, a ceramic laminate is produced.

[0140] The ceramic laminate is fired in a reducing atmosphere, wherein the reducing atmosphere is adjusted to be closer to the reduction side by 0.5 orders of magnitude than the equilibrium oxygen partial pressure at which Ni and NiO are in equilibrium, thereby producing a piezoelectric ceramic body (ceramic sintered body) containing an internal electrode layer mainly composed of Ni.

[0141] The two main surfaces of the obtained piezoelectric ceramic body were sputtered to form external electrodes made of Ag. Then, an electric field of 3 kV / mm was applied for 3 minutes in air at room temperature to perform polarization. In the above manner, samples No. 1 to 7 were prepared.

[0142] [Examples 1-2]

[0143] In Example 1-2, stacked piezoelectric elements with different Mn addition amounts were produced as shown in Table 3. The piezoelectric elements were produced by the same method as in Example 1-1 except that the ceramic stack was fired in a reducing atmosphere adjusted to be closer to the reduction side by one order of magnitude than the equilibrium oxygen partial pressure. In the above manner, samples No. 8 to 14 were produced.

[0144] [Example 2-1]

[0145] In Example 2-1, as shown in Table 4, the Mn addition amount was fixed at 5 mol%, and stacked piezoelectric elements with different NiO addition amounts were produced. As in Example 1-1, the ceramic stack was fired in a reducing atmosphere adjusted to be 0.5 orders of magnitude closer to the reduction side than the equilibrium oxygen partial pressure, thereby producing piezoelectric elements. In the above manner, sample numbers 15 to 22 were produced.

[0146] [Example 2-2]

[0147] In Example 2-2, as shown in Table 5, the Mn addition amount was fixed at 5 mol%, and stacked piezoelectric elements with different NiO addition amounts were produced. The piezoelectric elements were produced by the same method as in Example 2-1, except that the ceramic stack was fired in a reducing atmosphere adjusted to be closer to the reduction side by one order of magnitude than the equilibrium oxygen partial pressure. In the above manner, samples No. 23 to 30 were produced.

[0148] For each of the samples Nos. 1 to 30, a crystal structure analysis using X-ray diffraction was performed to analyze the crystal structure contained in the ceramic sintered body.

[0149] As a result, the main phase containing the KNN compound was confirmed to exist in the ceramic sintered body in samples 1 and 8 to which Mn was not added. On the other hand, the main phase containing the KNN compound, the second phase containing Mn and Nb, and the second phase containing Mn and Ni were confirmed to exist in the ceramic sintered body in samples 2 to 7 and 9 to 30 to which Mn was added.

[0150] In the crystal structure analysis using X-ray diffraction of each sample of sample numbers 1 to 30, when the maximum peak intensity of the main phase is defined as I0, the maximum peak intensity of the second phase containing Mn and Nb in the range of 2θ=33° to 35° is defined as I1, and the maximum peak intensity of the second phase containing Mn and Ni in the range of 2θ=41° to 44° is defined as I2, the maximum peak intensity ratio represented by I1 / I0 and the maximum peak intensity ratio represented by I2 / I0 are shown in Tables 2 to 5. It should be noted that, as described above, in samples 1 and 8, the peak of the second phase containing Mn and Nb and the peak of the second phase containing Mn and Ni were not detected, so the maximum peak intensity ratio is represented by "-".

[0151] The insulation performance of each sample No. 1 to 30 was evaluated by measuring the resistivity ρ (Ω·m) when a DC electric field of 3 kV / mm was applied at room temperature (25° C.), 85° C. or 125° C. The logρ value of each sample is shown in Tables 2 to 5.

[0152] The piezoelectric constant d was measured for each of the samples No. 1 to 30. 31 (pC / N), and the piezoelectric properties are evaluated from this. Piezoelectric constant d 31 The dielectric constant ε was measured by an impedance analyzer. 33 and electromechanical coupling coefficient k 31 The piezoelectric constant d of each sample is calculated. 31 The values ​​are shown in Tables 2 to 5.

[0153] [Table 2]

[0154]

[0155] [Table 3]

[0156]

[0157] [Table 4]

[0158]

[0159] [Table 5]

[0160]

[0161] In Tables 2 to 5, samples marked with an * are comparative examples outside the scope of the present invention.

[0162] The results in Tables 2 to 5 show that a second phase containing Mn and Nb is formed in the ceramic sintered body by firing the sintered product containing the main phase of the KNN-based compound to which Mn is added in a reducing atmosphere. Furthermore, by co-firing with a conductive layer (internal electrode layer) containing Ni as the main component, a second phase containing Mn and Ni is also formed in the ceramic sintered body.

[0163] According to Table 2, in samples 4 to 6 where the maximum peak intensity ratio represented by I1 / I0 is greater than 0.019 and less than 0.070, the resistivity logρ at 85°C is greater than 8.5, and the resistivity logρ at 125°C is greater than 7, which indicates sufficient insulation performance. In addition, in samples 2 to 6 where the maximum peak intensity ratio represented by I2 / I0 is greater than 0 and less than 0.04, the piezoelectric constant d 31 The piezoelectric properties are excellent when the value is greater than 40 pC / N. The same is true for Tables 3 to 5.

[0164] Explanation of symbols

[0165] 1.11 Piezoelectric ceramic body

[0166] 2, 2a, 2b, 12a, 12b external electrodes

[0167] 3. 3a~3h, 13 piezoelectric ceramic layers

[0168] 4. 4a~4g internal electrode layer

[0169] 5, 5a~5g, 7a ceramic green sheet

[0170] 6. 6a~6g conductive layer

[0171] 10, 20 Piezoelectric actuator (piezoelectric element)

Claims

1. A piezoelectric element comprising a piezoelectric ceramic layer, The piezoelectric ceramic layer is composed of a ceramic sintered body in which a main phase containing K, Na, Nb, and Mn and a secondary phase containing Mn and Nb exist.

2. The piezoelectric element according to claim 1, wherein The second phase containing Mn and Nb has a peak in the range of 2θ=33° to 35° in crystal structure analysis using X-ray diffraction.

3. The piezoelectric element according to claim 2, wherein: In the crystal structure analysis using X-ray diffraction, when the maximum peak intensity of the main phase is set to I0 and the maximum peak intensity in the range of 2θ=33°~35° of the second phase containing Mn and Nb is set to I1, the maximum peak intensity ratio represented by I1 / I0 is greater than 0.019 and less than 0.

070.

4. The piezoelectric element according to any one of claims 1 to 3, wherein The piezoelectric ceramic layer further includes an internal electrode layer provided on at least one main surface of the piezoelectric ceramic layer and containing Ni as a main component.

5. The piezoelectric element according to claim 4, wherein A second phase containing Mn and Ni also exists in the ceramic sintered body.

6. The piezoelectric element according to claim 5, wherein: The second phase containing Mn and Ni has a peak in the range of 2θ=41° to 44° in a crystal structure analysis using X-ray diffraction.

7. The piezoelectric element according to claim 6, wherein: In the crystal structure analysis using X-ray diffraction, when the maximum peak intensity of the main phase is set to I0 and the maximum peak intensity of the second phase containing Mn and Ni in the range of 2θ=41°~44° is set to I2, the maximum peak intensity ratio represented by I2 / I0 is greater than 0 and less than 0.

04.

8. A piezoelectric ceramic composition comprising a ceramic sintered body in which a main phase containing K, Na, Nb and Mn and a secondary phase containing Mn and Nb exist.

9. The piezoelectric ceramic composition according to claim 8, wherein: The second phase containing Mn and Nb has a peak in the range of 2θ=33° to 35° in crystal structure analysis using X-ray diffraction.

10. The piezoelectric ceramic composition according to claim 9, wherein In the crystal structure analysis using X-ray diffraction, when the maximum peak intensity of the main phase is set to I0 and the maximum peak intensity in the range of 2θ=33°~35° of the second phase containing Mn and Nb is set to I1, the maximum peak intensity ratio represented by I1 / I0 is greater than 0.019 and less than 0.

070.

11. The piezoelectric ceramic composition according to any one of claims 8 to 10, wherein A second phase containing Mn and Ni also exists in the ceramic sintered body.

12. The piezoelectric ceramic composition according to claim 11, wherein The second phase containing Mn and Ni has a peak in the range of 2θ=41° to 44° in a crystal structure analysis using X-ray diffraction.

13. The piezoelectric ceramic composition according to claim 12, wherein: In the crystal structure analysis using X-ray diffraction, when the maximum peak intensity of the main phase is set to I0 and the maximum peak intensity in the range of 2θ=41°~44° of the second phase containing Mn and Ni is set to I2, the maximum peak intensity ratio represented by I2 / I0 is less than 0.

04.

14. A method for manufacturing a piezoelectric element, comprising: A process of preparing a calcined product by mixing a K compound containing K, a Na compound containing Na, and a Nb compound containing Nb and calcining the mixture. a step of preparing a ceramic green sheet containing the calcined product and a Mn compound containing Mn, and A step of firing the ceramic green sheet in a reducing atmosphere.

15. The method for manufacturing a piezoelectric element according to claim 14, wherein: Before the step of firing the ceramic green sheet, a step of forming a conductive layer on the ceramic green sheet using a conductive paste containing Ni as a main component is further included.

16. The method for manufacturing a piezoelectric element according to claim 15, wherein: Before the step of firing the ceramic green sheets, the method further includes laminating the ceramic green sheets on which the conductive layers are formed to produce a ceramic laminate.

17. A method for producing a piezoelectric ceramic composition, comprising: A process of preparing a calcined product by mixing a K compound containing K, a Na compound containing Na, and a Nb compound containing Nb and calcining the mixture. a step of preparing a molded body containing the calcined product and a Mn compound containing Mn, and A step of firing the molded body in a reducing atmosphere.

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