Piezoelectric ceramic composition

Abstract

To provide a piezoelectric magnetic composition capable of achieving high piezoelectric properties, high Curie temperature, and high voltage resistance.SOLUTION: A piezoelectric magnetic composition is expressed by general formula: (PbxLa(1-x))y(ZrzTi(1-Z-W)Nbw)O3-δ, and is mainly composed of a compound in which x, y, z and w satisfy 0.95≤x≤0.98, 1.03≤y≤1.18, 0.52≤z≤0.57, 0.04≤w≤0.14, respectively.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a piezoelectric ceramic composition. [Background technology]

[0002] PZT (lead zirconate titanate) has traditionally been widely used as a ceramic that exhibits piezoelectricity, and various improvements have been made to enhance the piezoelectric properties of PZT. For example, it has been proposed to increase the dielectric constant, achieve a high piezoelectric constant, and achieve high coercive field strength by adding an appropriate amount of Nb2O5 in addition to adding La (lanthanum) to PZT. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-845 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a demand for applying this type of piezoelectric ceramic composition to piezoelectric elements with high amplitude and high reliability, and there is a need for the development of a piezoelectric ceramic composition that not only satisfies higher levels of piezoelectric properties but also has excellent voltage resistance performance. [Means for solving the problem]

[0005] The piezoelectric ceramic composition disclosed herein is a ceramic material having a general formula (Pb x La (1-x) ) y (Zr z Ti (1-Z-W) Nb w )O 3-δ and the main component is a compound represented by the formula (1) and in which x, y, z, and w satisfy the following conditions: 0.95≦x≦0.98, 1.03≦y≦1.18, 0.52≦z≦0.57, and 0.04≦w≦0.14. [Effects of the Invention]

[0006] The piezoelectric ceramic composition disclosed in this specification can achieve high piezoelectric properties, a high Curie temperature, and high voltage resistance. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is an image of the sintered body of Test Example 4 taken using a laser microscope. [Figure 2] FIG. 2 is an image of a sintered body of a conventional piezoelectric magnetic composition taken with a laser microscope. [Figure 3] FIG. 3 is a graph showing the relationship between the value of coefficient x in general formula (1) and the value of piezoelectric constant d33 in a test example. [Figure 4] FIG. 4 is a graph showing the relationship between the value of coefficient y in general formula (1) and the value of piezoelectric constant d33 in a test example. [Figure 5] FIG. 5 is a graph showing the relationship between the value of coefficient z in general formula (1) and the value of piezoelectric constant d33 in a test example. [Figure 6] FIG. 6 is a graph showing the relationship between the value of the coefficient w in the general formula (1) and the value of the piezoelectric constant d33 in a test example. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Outline of the embodiment] (1) The piezoelectric ceramic composition disclosed in the present specification is a ceramic material having a general formula (Pb x La (1-x) ) y (Zr z Ti (1-Z-W) Nb w )O 3-δ and the main component is a compound represented by the formula (1) and in which x, y, z, and w satisfy the following conditions: 0.95≦x≦0.98, 1.03≦y≦1.18, 0.52≦z≦0.57, and 0.04≦w≦0.14.

[0009] According to the above configuration, high piezoelectric properties, a high Curie temperature, and high breakdown voltage resistance can be achieved.

[0010] (2) In the piezomagnetic composition of (1) above, it is preferable that x, y, z, and w in the general formula satisfy 0.95 ≤ x ≤ 0.96, 1.03 ≤ y ≤ 1.18, 0.54 < z < 0.56, and 0.04 ≤ w ≤ 0.14.

[0011] [Details of Embodiment] Specific examples of the technology disclosed by this specification will be described below with reference to the drawings. Note that the present invention is not limited to these examples, and is indicated by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0012] [Configuration of Piezomagnetic Composition] The piezomagnetic composition of this embodiment has a compound represented by the following general formula (1) as the main component.

[0013] (Pb x La (1-x) ) y (Zr z Ti (1-Z-W) Nb w )O 3-δ …(1)

[0014] The compound represented by the general formula (1) above has a basic structure of PLZT (lead lanthanum zirconate titanate) in which part of Ti (titanium) in PZT is substituted with La, and Nb2O5 is added.

[0015] In the compound represented by the general formula (1) above, Pb (lead) and La are arranged at the A site of the perovskite structure, and Zr (zirconium), Ti, and Nb (niobium) are arranged at the B site.

[0016] The coefficients x, y, z, and w satisfy 0.95 ≦ x ≦ 0.98, 1.03 ≦ y ≦ 1.18, 0.52 ≦ z ≦ 0.57, and 0.04 ≦ w ≦ 0.14. More preferably, they satisfy 0.95 ≦ x ≦ 0.96, 1.03 ≦ y ≦ 1.18, 0.54 < z < 0.56, and 0.04 ≦ w ≦ 0.14.

[0017] If the coefficients x, y, z, and w take values within this range, high piezoelectric properties, a high Curie temperature, and high breakdown voltage can be achieved.

[0018] Among the coefficients 3 + δ of oxygen, the coefficient δ is a positive or negative value indicating oxygen deficiency or excess with respect to the coefficient of oxygen, which is usually 3. The coefficient 3 + δ of oxygen can take a value that allows the compound to form a perovskite-type oxide. A typical value of the coefficient δ is δ = 0, and 0 ≦ δ ≦ 0.1 is preferable. Note that the value of the coefficient δ can be calculated from the electrical neutrality condition of the composition of the compound. However, as the composition of the compound, a composition slightly deviating from the electrical neutrality condition is also acceptable.

[0019] [Manufacturing Method of Piezoelectromagnetic Composition] An example of the procedure for manufacturing the above piezoelectromagnetic composition is shown below.

[0020] First, weigh the raw material powders so as to obtain the target composition. The raw material powders may be oxides, carbonates, or hydroxides of each element contained in the target piezoelectromagnetic composition. Add a dispersion medium such as ethanol or water to these raw material powders and perform wet mixing using a ball mill to obtain a slurry. The mixed powder obtained by drying the resulting slurry is calcined, for example, at 600 - 1200 °C for 1 - 10 hours in an air atmosphere to obtain a calcined product.

[0021] Add a dispersant and a binder to the obtained calcined product and perform wet mixing to obtain a slurry. Dry the obtained slurry to obtain granulated powder.

[0022] The resulting granulated powder is molded into a predetermined shape to obtain a compact. The molding can be performed, for example, by uniaxial pressing. The resulting compact is degreased by, for example, holding it in an air atmosphere at 500-800°C for 2-100 hours, and then sintered at 900-1400°C for 1-10 hours to obtain a piezoelectric magnetic composition.

[0023] The above-described manufacturing method is an example, and various other steps and processing conditions can be used to manufacture the piezoelectric magnetic composition.

[0024] The piezoelectric ceramic composition of this embodiment can be widely used in vibration detection applications, pressure detection applications, oscillation applications, piezoelectric device applications, etc. For example, it can be used in sensors that detect various vibrations (knock sensors, combustion pressure sensors, etc.), piezoelectric devices such as vibrators, actuators, and filters, high-voltage generators, micropower sources, various drive devices, position control devices, vibration suppression devices, fluid discharge devices (paint discharge, fuel discharge, etc.), etc. The piezoelectric ceramic composition of this embodiment is particularly suitable for applications requiring high amplitude and high reliability (high voltage resistance and drive durability).

[0025] [Test example] 1. Sample preparation PbO powder, ZrO2 powder, TiO2 powder, La(OH)3 powder, and Nb2O5 powder were each weighed and mixed so that the coefficients x, y, z, and w in the following general formula would have the target values.

[0026] (Pb x La (1-x) ) y (Zr z Ti (1-Z-W) Nb w )O 3-δ …(1)

[0027] Ethanol was added to a mixture of these raw material powders and wet-mixed in a ball mill for 15 hours or more to obtain a slurry. The resulting slurry was dried, and the resulting mixed powder was calcined in air at 600-1200°C for 1-10 hours to obtain a calcined powder. 10 mm diameter YTZ balls, binder, and water were added to the resulting calcined powder, and the mixture was pulverized and mixed until the average particle size D50 of the calcined powder was 0.9 μm or less and the span (D90-D10 / D50) was 2.2 μm or more to obtain a slurry. The resulting slurry was dried to obtain a granulated powder.

[0028] The resulting granulated powder was uniaxially pressed at a pressure of 150 MPa using a 30 mm diameter die to form a disk-shaped compact, which was then degreased by holding at 500-800°C in air for 2-100 hours, and then sintered at 900-1400°C for 1-10 hours to obtain a sintered piezoelectric magnetic composition.

[0029] Electrodes were formed on both the front and back sides of the obtained sintered body, and the sintered body after the electrode formation was subjected to polarization treatment by applying a DC voltage of 2.5 kv / mm in silicone oil at 80°C to obtain a piezoelectric element.

[0030] 2. Test Method (1) Structural analysis The obtained sintered body was mirror-polished and then observed using a laser microscope (Keyence VK-X100). XRD (X-ray Diffraction) confirmed that the sintered body had only one phase of perovskite structure, and then XRF (X-ray Fluorescence) was used to analyze the composition and determine the values ​​of the coefficients x, y, z, and w in general formula (1).

[0031] (2) Piezoelectric properties The piezoelectric element was formed into a disk shape with a thickness of 2 mm and a diameter of 25 mm. The piezoelectric constant d 33 is d 33 The electromechanical coupling coefficient kr and relative permittivity ε were measured using a dielectric constant meter (ZJ-4B, manufactured by INSTITUTE OF ACADEMIA AINICA). 33T The relative permittivity ε / ε was measured using an impedance analyzer (Keysight Corporation, E4990A). 33 T / ε0 was plotted, and the temperature at which it peaked was taken as the Curie temperature Tc.

[0032] (3) Voltage resistance A piezoelectric element was used, which consisted of a sintered body formed into a disk shape with a thickness of 1 mm and a diameter of 16 mm, with 14 mm diameter electrodes baked onto both surfaces. A voltage was applied to the piezoelectric element, and the voltage was gradually increased until a leakage current began to flow, at which point the voltage was measured.

[0033] (4) Specific gravity The specific gravity of the resulting sintered body was calculated by Archimedes' method.

[0034] 3.Results For each test example, the values ​​of the coefficients x, y, z, and w determined by composition analysis and the test results are shown in Table 1.

[0035] [Table 1]

[0036] From Table 1, in Test Example 1, in which the coefficient x in the general formula (1) was 0.94, the electromechanical coupling constant kr was 56% and the Curie temperature Tc was low at 190°C. 3 The Curie temperature Tc was as low as 200°C, and a leakage current was observed at 4.8 kv / mm, indicating low voltage resistance. Test Example 25, in which the coefficient w in the general formula (1) was 0.16, also had a low Curie temperature Tc of 200°C.

[0037] In Test Example 2-24, where the coefficients x, y, z, and w in the general formula (1) were 0.95≦x≦0.98, 1.03≦y≦1.18, 0.52≦z≦0.57, and 0.04≦w≦0.14, a high Curie temperature Tc exceeding 200°C was achieved. 3As described above, a dense sintered body was obtained. Also, observation with a laser microscope confirmed that the obtained sintered body (see Fig. 1) had a denser structure than the conventional piezoelectric magnetic composition (see Fig. 2). The voltage at which leakage current was observed was 6.4 kV / mm or higher, indicating that high breakdown voltage performance was achieved.

[0038] Furthermore, in Test Examples 2-4, 8-13, and 20-24 where the coefficients x, y, z, and w in the general formula (1) satisfy 0.95 ≤ x ≤ 0.96, 1.03 ≤ y ≤ 1.18, 0.54 < z < 0.56, and 0.04 ≤ w ≤ 0.14, as shown in Table 1 and Figs. 3-6, the piezoelectric constant d 33 was 600 pC / N or higher, indicating that it was confirmed that high piezoelectric constant d 33 and high Curie temperature Tc could be achieved simultaneously.

Claims

1. General formula (Pb ｘ La （１－ｘ） ) ｙ (Zr ｚ Ti （１－Ｚ－Ｗ） Nb ｗ ) O ３－δ and x, y, z, and w satisfy 0.95≦x≦0.98, 1.03≦y≦1.18, 0.52≦z≦0.57, and 0.04≦w≦0.

14.

2. 2. The piezoelectric ceramic composition according to claim 1, wherein x, y, z, and w in said general formula satisfy 0.95≦x≦0.96, 1.03≦y≦1.18, 0.54<z<0.56, and 0.04≦w≦0.14.

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