Lead-free piezoelectric ceramic composition and piezoelectric element

Abstract

The lead-free piezoelectric ceramic composition comprises: a main phase formed of an alkali niobate perovskite-type oxide represented by the composition formula (A1 a M1 b ) c (Nb d1 , Mn d2 , M2 d3 )O 3+e (wherein, element A1 is at least one of alkali metals, element M1 is at least one of Ba, Ca, and Sr, element M2 is at least one of Ti and Zr, a, b, c, d1, d2, d3, and e satisfy 0 < a < 1, 0 < b < 1, a + b = 1, 0.80 < c < 1.10, 0 < d1 < 1, 0 < d2 < 1, 0 < d3 < 1, d1 + d2 + d3 = 1, and e is a value indicating oxygen deficiency or excess), and b / (d2 + d3) > 1.0 is satisfied.

Description

Technical Field

[0001] The technology disclosed in this specification relates to lead-free piezoelectric ceramic compositions and piezoelectric elements. Background Technology

[0002] Previously, lead zirconate titanate (PZT) has been widely used as a ceramic exhibiting piezoelectric properties. However, PZT contains lead, thus its environmental impact is considered a concern. In recent years, the development of lead-free piezoelectric ceramic raw materials has been promoted. As one of the promising candidates for lead-free piezoelectric ceramic raw materials, lead-free piezoelectric ceramic compositions with alkali niobate perovskite oxide as the main phase are available.

[0003] To use this lead-free piezoelectric ceramic composition in piezoelectric filters, piezoelectric oscillators, piezoelectric transformers, piezoelectric ultrasonic motors, piezoelectric gyroscope sensors, knock sensors, etc., a high mechanical quality factor Qm is required. It is known that a lead-free piezoelectric ceramic composition with a high mechanical quality factor Qm can be obtained by adding manganese (Mn) to an alkaline niobate perovskite oxide (see Patent Document 1).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 4929522 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] There is a desire to use the above-mentioned lead-free piezoelectric ceramic composition in piezoelectric elements requiring a high mechanical quality factor Qm, such as bolt-fastened Langevin-type ultrasonic transducers, and there is a need to further improve the properties of the lead-free piezoelectric ceramic composition.

[0009] Solution for solving the problem

[0010] The lead-free piezoelectric ceramic composition disclosed in this specification comprises: a composition of formula (A1) a M1 b ) c (Nb d1 Mn d2 M2 d3 )O 3+e(Wherein, element A1 is at least one of alkali metals, element M1 is at least one of Ba, Ca, and Sr, element M2 is at least one of Ti and Zr, 0 < a < 1, 0 < b < 1, a + b = 1, c satisfies 0.80 < c < 1.10, 0 < d1 < 1, 0 < d2 < 1, 0 < d3 < 1, d1 + d2 + d3 = 1, and e is a value representing oxygen deficiency or excess) a main phase formed of an alkali niobate perovskite-type oxide, and b / (d2 + d3) > 1.0 is satisfied.

[0011] In addition, the piezoelectric element disclosed in this specification includes: a piezoelectric body formed of the above lead-free piezoelectric ceramic composition, and an electrode in contact with the piezoelectric body.

[0012] Effects of the Invention

[0013] According to the lead-free piezoelectric ceramic composition and piezoelectric element disclosed in this specification, a high mechanical quality factor Qm can be achieved. Description of the Drawings

[0014] Figure 1 A perspective view of the piezoelectric element of the embodiment. Detailed Embodiments

[0015] [Summary of the Embodiment]

[0016] (1) The lead-free piezoelectric ceramic composition disclosed in this specification includes: composed of the compositional formula (A1 a M1 b ) c (Nb d1 , Mn d2 , M2 d3 )O 3+e (Wherein, element A1 is at least one of alkali metals, element M1 is at least one of Ba, Ca, and Sr, element M2 is at least one of Ti and Zr, 0 < a < 1, 0 < b < 1, a + b = 1, c satisfies 0.80 < c < 1.10, 0 < d1 < 1, 0 < d2 < 1, 0 < d3 < 1, d1 + d2 + d3 = 1, and e is a value representing oxygen deficiency or excess) a main phase formed of an alkali niobate perovskite-type oxide, and b / (d2 + d3) > 1.0 is satisfied.

[0017] In addition, the piezoelectric element disclosed in this specification includes: a piezoelectric body formed of the above lead-free piezoelectric ceramic composition, and an electrode in contact with the piezoelectric body.

[0018] It is believed that in alkali niobate perovskite oxides, Mn acts as an acceptor, dissolving at Nb sites, thereby improving the mechanical quality factor Qm. However, Mn is less soluble than alkali niobate perovskite oxides and tends to segregate as a heterogeneous phase in lead-free piezoelectric ceramic compositions. On the other hand, it is speculated that when divalent elements with valences close to Mn, namely Ba, Ca, and Sr, dissolve at alkali sites, Mn facilitates dissolution at Nb sites. It is suggested that by adjusting the composition ratio of Mn to Ba, Ca, and Sr to achieve b / (d2+d3)>1.0, an appropriate amount of Mn can dissolve at Nb sites, thus improving the mechanical quality factor Qm.

[0019] (2) The lead-free piezoelectric ceramic composition of (1) above may contain a composition of formula A2 1-x Ti 1-x Nb 1+x The secondary phase is formed by an oxide of one of the following: an oxide of the formula O5 (wherein element A2 is at least one of the alkali metals, satisfying 0≤x≤0.15) and an oxide of the formula A3Ti3NbO9 (wherein element A3 is at least one of the alkali metals).

[0020] Based on this configuration, the piezoelectric properties can be improved compared to lead-free piezoelectric ceramic compositions that do not have a secondary phase.

[0021] (3) In the lead-free piezoelectric ceramic composition of (1) above, the average particle size of the crystal particles of the aforementioned alkaline niobate perovskite oxide contained in the aforementioned main phase can be 0.3 μm or more and 3.5 μm or less.

[0022] Alternatively, in the lead-free piezoelectric ceramic composition of (1) above, the average particle size of the crystal particles of the aforementioned alkaline niobate perovskite oxide contained in the aforementioned main phase may be 0.3 μm or more and 1.1 μm or less.

[0023] Based on this configuration, the mechanical quality factor Qm is further improved.

[0024] [Detailed Implementation]

[0025] Specific examples of the technology disclosed in this specification will be described below with reference to the accompanying drawings. It should be noted that the invention is not limited to these examples and is intended to include all modifications expressed in, and equivalent to, the claims.

[0026] <Implementation Method>

[0027] [Composition of lead-free piezoelectric ceramic composition]

[0028] The lead-free piezoelectric ceramic composition of the present embodiment contains a main phase formed of an alkaline niobate perovskite-type oxide having piezoelectric properties. The alkaline niobate perovskite-type oxide of the present embodiment is represented by the following compositional formula (1).

[0029] (A1 a M1 b ) c (Nb d1 , Mn d2 , M2 d3 )O 3+e …(1)

[0030] [[ID=***]]Element A1 is at least one of alkali metals. Element M1 is at least one of Ca (calcium), Sr (strontium), and Ba (barium) belonging to alkaline earth metals. Element M2 is at least one of Ti (titanium) and Zr (zirconium).

[0031] In the above compositional formula (1), element A1 and element M1 are arranged at the A site (alkali site) of the perovskite structure, and Nb (niobium), Mn (manganese), and element M2 are arranged at the B site.

[0032] As the values of coefficients a to e in the above compositional formula (1), preferred values are selected from combinations of values that enable the formation of the perovskite structure, from the viewpoint of the electrical properties or piezoelectric properties (particularly the piezoelectric constant d 33 ) of the lead-free piezoelectric ceramic composition.

[0033] Specifically, coefficients a and b satisfy 0 < a < 1, 0 < b < 1, and a + b = 1, excluding a = 0 (i.e., a composition containing no alkali metals) and b = 0 (i.e., a composition containing no Ca, Sr, or Ba).

[0034] Coefficient c for the entire A site satisfies 0.80 < c < 1.10, preferably 0.84 ≤ c ≤ 1.08, and more preferably 0.88 ≤ c ≤ 1.07.

[0035] Coefficients d1, d2, and d3 satisfy 0 < d1 < 1, 0 < d2 < 1, 0 < d3 < 1, and d1 + d2 + d3 = 1. Exclude d1 = 0 (a composition containing no Nb), d2 = 0 (a composition containing no Mn), and d3 = 0 (a composition containing neither Ti nor Zr).

[0036] In the coefficient 3 + e of oxygen, coefficient e is the coefficient of oxygen, which is usually 3, and is a positive or negative value indicating oxygen deficiency or excess. The coefficient (3 + e) of oxygen can take a value that forms the perovskite oxide of the main phase. A typical value of coefficient e is e = 0, preferably 0 ≤ e ≤ 0.1. It should be noted that the value of coefficient e can be calculated from the electrical neutrality condition of the composition of the main phase. Among them, as the composition of the main phase, a composition slightly deviating from the electrical neutrality condition is also allowed.

[0037] The coefficients b, d2, and d3 satisfy b / (d2 + d3) > 1.0. When the coefficients b, d2, and d3 take values within this range, a lead-free piezoelectric ceramic composition with a high mechanical quality factor Qm is obtained. The reason is speculated as follows.

[0038] It is considered that Mn is dissolved as an acceptor in the sites of Nb, thereby improving the mechanical quality factor Qm. However, Mn is not easily dissolved in alkaline niobate perovskite-type oxides and tends to segregate as a heterogeneous phase in the lead-free piezoelectric ceramic composition. It is considered that the ease of dissolution depends on the ionic radius and valence of the dissolved metal atoms. It is considered that trivalent Mn is not easily dissolved in the B site mainly coordinated with pentavalent Nb. On the other hand, divalent elements such as Ba, Ca, and Sr are easily dissolved in the A site coordinated with monovalent alkali metals. Moreover, it is speculated that when Ba, Ca, and Sr with valences close to Mn are dissolved in the A site in an appropriate amount, it helps Mn to be dissolved in the B site. It is considered that by adjusting the composition ratio of Mn to Ba, Ca, and Sr to make b / (d2 + d3) > 1.0, an appropriate amount of Mn is dissolved in the B site, and the mechanical quality factor Qm is improved.

[0039] There is no particular limitation on the upper limit value of b / (d2 + d3), and preferably b / (d2 + d3) ≤ 2.0.

[0040] The alkaline niobate perovskite-type oxide represented by the above compositional formula (1) preferably contains at least one of K (potassium), Na (sodium), and Li (lithium) as element A1. When the oxide contains at least one of K, Na, and Li as element A1, at least one of Ca, Sr, and Ba as element M1, and at least one of Ti and Zr as element M2, the compositional formula (1) can be replaced as the following compositional formula (1a).

[0041] (K a1 Na a2 Li a3 Ca b1 , Sr b2 , Ba b3 ) c (Nb d1 , Mn d2 , Ti d31 , Zr d32 )O 3+e …(1a)

[0042] The above compositional formulas (1) and (1a) are equivalent, with a1 + a2 + a3 = a, b1 + b2 + b3 = b, and d31 + d32 = d. The coefficients a1 and a2 of K and Na are typically 0 < a1 ≤ 0.6, 0 < a2 ≤ 0.6. The coefficient a3 of Li can also be zero, but preferably 0 < a3 ≤ 0.2, and more preferably 0 < a3 ≤ 0.1.

[0043] In the alkali niobate perovskite oxides shown in formula (1a) above, oxides with K, Na, and Nb as the main metal components are called "KNN" or "KNN material". By using this oxide, lead-free piezoelectric ceramic compositions with excellent piezoelectric properties, electrical properties, insulation, and high-temperature durability, and without drastic changes in properties between -50°C and +150°C, can be obtained. A typical composition of the main phase is (K, Na, Li, Ca, Ba). c (Nb, Mn, Ti, Zr)O 3+e .

[0044] The lead-free piezoelectric ceramic composition of this embodiment may contain a secondary phase formed from an oxide of one of the following compositional formula (2) or an oxide of the following compositional formula (3).

[0045] A2 1-x Ti 1-x Nb 1+x O5…(2)

[0046] A3Ti3NbO9…(3)

[0047] In formula (2), element A2 is at least one of the alkali metals, preferably at least one of K, Rb (rubidium), and Cs (cesium). The coefficient x satisfies 0 ≤ x ≤ 0.15. If the coefficient x takes a value within this range, the structure of the secondary phase is stable, and a uniform crystalline phase can be obtained. From the viewpoint of the structural stability of the secondary phase, for the coefficient x, when element A2 is K or Rb, it is preferable to satisfy 0 ≤ x ≤ 0.15, and when element A2 is Cs, it is preferable to satisfy 0 ≤ x ≤ 0.10.

[0048] In the composition formula (3), element A3 is at least one of the alkali metals, preferably at least one of K, Rb and Cs.

[0049] The secondary phase does not possess piezoelectric properties, but its presence, mixed with the main phase, improves sinterability and insulation. Furthermore, it is believed to contribute to preventing a phase transition point between -50°C and +150°C. The secondary phase is a layered compound (or a layered compound), presumed to be a layered compound, which improves the insulation of the piezoelectric ceramic composition and helps prevent a phase transition point.

[0050] The content of the secondary phase can be greater than 0 mol% and less than 20 mol%, but preferably more than 2 mol% and less than 15 mol%, and even more preferably more than 2 mol% and less than 10 mol%.

[0051] The oxides with Nb, Ti, and K as the main metal components in the oxides shown in formula (2) or (3) are called "NTN materials". By using the oxides, inexpensive lead-free piezoelectric ceramic compositions with excellent piezoelectric properties can be obtained.

[0052] [Piezoelectric element 10]

[0053] The piezoelectric element 10 of this embodiment includes a piezoelectric body 11 and electrodes 12 and 13 in contact with the piezoelectric body 11. The piezoelectric body 11 is made of the lead-free piezoelectric ceramic composition described above and is in the shape of a circular plate. One of the electrodes 12 and 13 is disposed on one side of the piezoelectric body 11 and the other is disposed on the other side of the piezoelectric body 11, so that the piezoelectric body 11 is sandwiched between the electrodes 12 and 13.

[0054] The following shows an example of a method for manufacturing the piezoelectric element 10 described above.

[0055] First, the desired components are selected from the raw material powder of the main phase and weighed in a manner that forms the target composition. The raw material powder can be oxides, carbonates, or hydroxides of the elements contained in the main phase. Ethanol is added to these raw material powders, and wet mixing is carried out in a ball mill, preferably for more than 15 hours, to obtain a slurry. The obtained slurry is dried to obtain a mixed powder, and the obtained mixed powder is pre-calcined, for example, at 600–1000°C for 1–10 hours under atmospheric conditions, to obtain a pre-calcined main phase.

[0056] In addition, the desired components are selected from the raw material powder of the secondary phase and weighed in a manner that forms the target composition. The raw material powder can be oxides, carbonates, or hydroxides of the elements contained in the secondary phase. Then, ethanol is added to these raw material powders, and wet mixing is carried out in a ball mill, preferably for 15 hours or more, to obtain a slurry. The obtained slurry is dried to obtain a mixed powder, and the obtained mixed powder is pre-calcined, for example, at 600–1000°C for 1–10 hours under atmospheric atmosphere, to obtain a pre-calcined secondary phase.

[0057] Next, the primary phase pre-calcined material and the secondary phase pre-calcined material are weighed separately, and in a ball mill, a dispersant, binder, and ethanol are added and pulverized / mixed to form a slurry. Additionally, if necessary, raw material powders not selected in the above-mentioned primary phase pre-calcined material and secondary phase pre-calcined material steps can be weighed from the primary or secondary phase raw material powders and added to the slurry. It should be noted that this slurry can be pre-calcined again and then pulverized and mixed. The resulting slurry is dried and granulated, for example, by uniaxial pressing at a pressure of 20 MPa to form the desired shape. The resulting molded body is subjected to CIP (cold isostatic pressing) treatment, for example, at a pressure of 150 MPa. The resulting CIP pressed body is then fired, for example, at 900–1300 °C for 1–10 hours in an atmospheric atmosphere to obtain a piezoelectric body. This firing can be carried out in an oxygen atmosphere.

[0058] For example, electrodes can be formed on the surface of the obtained piezoelectric material by sputtering, and then polarization treatment can be performed to obtain a piezoelectric element.

[0059] It should be noted that the above manufacturing method is one example, and various other processes and conditions used in manufacturing piezoelectric elements can be utilized. For example, the raw materials can be mixed and fired in proportions consistent with the final lead-free piezoelectric ceramic composition, instead of pre-forming the main phase and secondary phase separately and then mixing and firing their powders. The method of mixing the main phase and secondary phase after pre-forming the main phase and secondary phase separately allows for more precise control of their composition, thus improving the yield of the lead-free piezoelectric ceramic composition.

[0060] The lead-free piezoelectric ceramic composition and piezoelectric element of this embodiment can be widely used in vibration detection, pressure detection, oscillation, and piezoelectric device applications. For example, they can be used in sensors for detecting various vibrations (knock sensors and combustion pressure sensors, etc.), piezoelectric devices such as oscillators, drivers, and filters, high-voltage generators, micro-power supplies, various drive devices, position control devices, vibration suppression devices, and fluid discharge devices (paint discharge and fuel discharge, etc.). Furthermore, the lead-free piezoelectric ceramic composition and piezoelectric element of this embodiment are particularly suitable for applications requiring excellent thermal durability (e.g., knock sensors and combustion pressure sensors).

[0061] <Experimental Example>

[0062] 1. Sample preparation

[0063] (1) First pre-calcination process

[0064] K2CO3 powder, Na2CO3 powder, Li2CO3 powder, and Nb2O5 powder were weighed respectively in the manner that the coefficients f, g, and h of the following composition formula (4) are in the ratios shown in Table 1.

[0065] (K f Na g Li h NbO3…(4)

[0066] [Table 1]

[0067] Sample No. f g h 1 0.47 0.51 0.02 2 0.47 0.51 0.02 3 0.47 0.51 0.02 4 0.47 0.51 0.02 5 0.48 0.52 0.00 6 0.47 0.51 0.02 7 0.47 0.51 0.02 8 0.47 0.51 0.02 9 0.47 0.51 0.02 10 0.47 0.51 0.02 11 0.47 0.51 0.02 12 0.47 0.51 0.02 13 0.47 0.51 0.02 14 0.10 0.88 0.02

[0068] Ethanol is added to these raw material powders, and the mixture is wet-mixed in a ball mill for more than 15 hours to obtain a slurry. The slurry is dried to obtain a mixed powder, which is then pre-calcined at 600-1000℃ for 1-10 hours under atmospheric conditions to obtain the first pre-calcined powder.

[0069] (2) Second pre-calcination process

[0070] Select the desired powder from CaCO3 powder, SrCO3 powder, BaCO3 powder, MnO2 powder, TiO2 powder, and ZrO2 powder, weigh them such that the molar percentage of metal atoms in each powder relative to the first precalcined powder (the oxide shown in the above composition formula (4)) is the value shown in Table 2, and add them to the first precalcined powder.

[0071] [Table 2]

[0072]

[0073] Ethanol is added to the mixture of these raw material powders and the first precalcined powder, and the mixture is wet-mixed in a ball mill for more than 15 hours to obtain a slurry. The slurry is dried to obtain a mixed powder, which is then precalcined at 600-1000℃ for 1-10 hours under atmospheric conditions to obtain the second precalcined powder.

[0074] (3) Molding process

[0075] Dispersant, binder, and ethanol are added to the obtained second precalcined powder and then pulverized / mixed to form a slurry. The slurry is dried, granulated, and uniaxially pressed at a pressure of 20 MPa to form a circular plate. Then, it is subjected to CIP (cold isostatic pressing) at a pressure of 150 MPa to obtain the molded body.

[0076] (4) Formal firing process

[0077] The resulting molded body is held at 1000-1300°C for 1-10 hours in an atmospheric atmosphere and then fired to obtain a piezoelectric body. This piezoelectric body is composed of a lead-free piezoelectric ceramic composition formed from an alkaline niobate perovskite oxide as shown in the above-described formula (1a).

[0078] (5) Electrode forming process

[0079] Au-containing electrodes were formed on both the inner and outer surfaces of the obtained piezoelectric material by sputtering. The piezoelectric material with the electrodes formed was then subjected to electrolysis at 5 kV / mm in silicone oil at 50°C for polarization treatment, yielding sample No. 1-14.

[0080] 2. Test Methods

[0081] The obtained samples were measured using an impedance analyzer (Keysight Technologies, E4990A), and the relative permittivity ε was calculated from the capacitance value at room temperature and 1 kHz. 33 T / ε0. Additionally, the mechanical quality factor Qm is calculated using the resonance-anti-resonance method. Products with a mechanical quality factor Qm value of 500 or higher are judged as good products.

[0082] 3. Results

[0083] For each sample, the total molar percentage of Ba atoms, Ca atoms, and Sr atoms in the raw material powder added relative to the first pre-calcined powder in 1.(2) above is set as P. M1 Let the total molar percentage of Ti atoms and Zr atoms be P. M2 Let the molar percentage of Mn atoms be P. Mn Find P M1 / (P M2 +P Mn The value of ) is calculated and compared with the relative permittivity ε. 33 T The values ​​of / ε0 and the mechanical quality factor Qm are shown together in Table 3.

[0084] [Table 3]

[0085]

[0086] Theoretically, all Ba, Ca, and Sr atoms in the raw material powder enter the A site of the obtained alkali niobate perovskite oxide. Furthermore, all Mn, Ti, and Zr atoms enter the B site of the obtained alkali niobate perovskite oxide. Therefore, the molar percentages of Ba, Ca, Sr, Mn, Ti, and Zr atoms can be considered to correspond to the coefficients b1, b2, b3, d2, d31, and d32 of Ba, Ca, Sr, Mn, Ti, and Zr in the above composition formula (1a), respectively. Moreover, the total molar percentages P of Ba, Ca, and Sr atoms can be considered to be... M1The total value of the coefficients b1, b2, and b3 of Ba, Ca, and Sr in the above composition formula (1a) (the value of coefficient b in composition formula (1)) can be considered as the total molar percentage P of Ti atoms and Zr atoms. M2 The total value of coefficients d31 and d32 corresponding to Ti and Zr in the above composition formula (1a) (the value of coefficient d3 in composition formula (1)). From the above, it can be considered that the molar percentage relationship P M1 / (P M2 +P Mn The relationship between the coefficients b, d2, and d3 in composition (1) is equivalent to b / (d2+d3).

[0087] P M1 / (P M2 +P Mn For samples No. 1-3, the mechanical quality factor Qm is less than 500 when the value of b / (d2+d3) is less than 1.0. In contrast, P... M1 / (P M2 +P Mn The mechanical quality factor Qm of sample No. 4-14, whose value of b / (d2+d3) exceeds 1.0, is above 500, indicating excellent piezoelectric properties.

[0088] Additional experimental examples to investigate the relationship between the average particle size of crystals and the mechanical quality factor Qm.

[0089] 1. Sample preparation and testing methods

[0090] In the first precalcination step, each raw material powder is weighed in such a way that the coefficients f, g, and h of the above composition formula (4) are in the ratio shown in Table 4. In the second precalcination step, the raw material powder is weighed in such a way that the molar percentage of metal atoms in the raw material powder added in the first precalcination powder is in the ratio shown in Table 4. Otherwise, the samples are prepared in the same way as the above test example to obtain sample No. 15-22.

[0091] [Table 4]

[0092]

[0093] For samples No. 15-22 and samples No. 1 and 4 of the above test examples, SEM images were taken at 10,000x magnification. The obtained images were processed using ImageJ software, and the average particle size of the crystal particles contained in the image (10 μm × 10 μm) was taken as the average particle size. Furthermore, the relative permittivity ε was calculated using the same method as in the above test examples. 33 T / ε0 and mechanical quality factor Qm. Products with a mechanical quality factor Qm value of 500 or above are judged as good products.

[0094] 2. Results

[0095] For each sample, the values ​​of average particle size, relative permittivity, and mechanical quality factor Qm are shown in Table 5.

[0096] [Table 5]

[0097]

[0098] P M1 / (P M2 +P Mn The mechanical quality factor Qm of samples No. 1, 21, and 22, whose values ​​of ) (i.e., b / (d2+d3)) are below 1.0, is significantly lower than 500. Additionally, P M1 / (P M2 +P Mn The mechanical quality factor Qm of sample No. 20, where the value of b / (d2+d3) exceeds 1.0 and the average grain size of the crystal particles of the alkali niobate perovskite oxide is 3.8 μm, is slightly below 500. In contrast, P... M1 / (P M2 +P Mn The mechanical quality factor Qm of samples No. 4, 15, and 19 (i.e., the value of b / (d2+d3)) exceeds 1.0, and the average particle size of the crystal grains of alkali niobate perovskite oxides is 0.3-3.5 μm, is above 500, indicating excellent piezoelectric properties. In particular, the mechanical quality factor Qm of samples No. 15-17 (i.e., the average particle size of the crystal grains of alkali niobate perovskite oxides) is above 560, indicating exceptionally excellent piezoelectric properties.

[0099] Explanation of reference numerals in the attached figures

[0100] 10: Piezoelectric elements

[0101] 11: Piezoelectric element

[0102] 12, 13: Electrodes

Claims

1. A lead-free piezoelectric ceramic composition comprising: a composition of formula (A1) a M1 b ) c (Nb d1 Mn d2 M2 d3 )O 3+e The main phase shown is formed by alkali niobate perovskite oxides, wherein... Element A1 is Na and K, or element A1 is Na, K, and Li, element M1 is at least one of Ba, Ca, and Sr, element M2 is at least one of Ti and Zr, 0 < a < 1, 0 < b < 1, a + b = 1, c satisfies 0.80 < c < 1.10, 0 < d1 < 1, 0 < d2 < 1, 0 < d3 < 1, d1 + d2 + d3 = 1, and e is a value representing oxygen deficiency or excess. And it satisfies b / (d2 + d3) > 1.

0.

2. The lead-free piezoelectric ceramic composition according to claim 1, comprising: a composition of formula A2 1-x Ti 1-x Nb 1+x The secondary phase formed by the oxide shown in O5 and the oxide with the composition A3Ti3NbO9, wherein... Element A2 is at least one of alkali metals, satisfying 0 ≤ x ≤ 0.15, and element A3 is at least one of alkali metals.

3. The lead-free piezoelectric ceramic composition according to claim 1 or 2, wherein, The average particle size of the crystal grains of the alkali niobate perovskite-type oxide contained in the main phase is 0.3 μm or more and 3.5 μm or less.

4. The lead-free piezoelectric ceramic composition according to claim 1 or 2, wherein, The average particle size of the crystal grains of the alkali niobate perovskite-type oxide contained in the main phase is 0.3 μm or more and 1.1 μm or less.

5. A piezoelectric element, comprising: a piezoelectric body formed of the lead-free piezoelectric ceramic composition according to any one of claims 1 to 4, and an electrode in contact with the piezoelectric body.

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