JP4479089B2 - Piezoelectric ceramic composition and piezoelectric ceramic element using the same - Google Patents

Description

試料 No.欄の＊印はその試料がこの発明の範囲外であることを示す。
【００１０】
表１に示すように、この発明の実施例にかかる各試料については、いずれも、電気機械結合係数ｋｔが２０％以上と実用レベルにありかつ共振周波数の温度変化率ｆｒＴＣが４５以下と実用レベルにあることから、特にたとえば、圧電セラミックフィルタ、圧電セラミック発振子および圧電セラミック振動子などの圧電セラミック素子などの材料として有用な圧電磁器組成物であることが明らかである。
また、表１に示すように、Ｙを含む場合、すなわち、この発明の実施例の試料 No.２、３および５においては、共振周波数の温度変化率ｆｒＴＣが特に小さい有用な圧電磁器が得られることが明らかである。
【００１１】
なお、この発明にかかる圧電磁器組成物は上記の実施例の組成に限定されるものではなく、発明の要旨の範囲内であれば有効である。
【００１２】
また、上述の実施例では電気機械結合係数ｋｔおよび共振周波数の温度変化率ｆｒＴＣは円板状の圧電セラミック振動子の厚み縦振動についての例を示したが、本願発明の効果は、円板状の圧電セラミック振動子の厚み縦振動に限定されず、厚みすべり振動や厚み縦振動の高調波など、他の圧電セラミック素子として特にたとえば圧電セラミックフィルタや圧電セラミック発振子などに利用される他の振動モードにおいても、厚み縦振動の場合と同様に有効である。
【００１３】
図１はこの発明にかかる圧電セラミック振動子の一例を示す斜視図であり、図２はその断面図解図である。図１および図２に示す圧電セラミック振動子１０は、たとえば直方体状の圧電磁器１２を含む。圧電磁器１２は、２枚の圧電磁器層１２ａおよび１２ｂを含む。これらの圧電磁器層１２ａおよび１２ｂは、上述のこの発明にかかる圧電磁器組成物からなり、積層されかつ一体的に形成される。また、これらの圧電磁器層１２ａおよび１２ｂは、図２の矢印で示すように、同じ厚み方向に分極されている。
【００１４】
圧電磁器層１２ａおよび１２ｂの間には、その中央にたとえば円形の振動電極１４ａが形成され、その振動電極１４ａから圧電磁器１２の一端面にわたってたとえばＴ字形の引出電極１６ａが形成される。また、圧電磁器層１２ａの表面には、その中央にたとえば円形の振動電極１４ｂが形成され、その振動電極１４ｂから圧電磁器１２の他端面にわたってたとえばＴ字形の引出電極１６ｂが形成される。さらに、圧電磁器層１２ｂの表面には、その中央にたとえば円形の振動電極１４ｃが形成され、その振動電極１４ｃから圧電磁器１２の他端面にわたってたとえばＴ字形の引出電極１６ｃが形成される。
【００１５】
そして、引出電極１６ａにはリード線１８ａを介して一方の外部端子２０ａが接続され、引出電極１６ｂおよび１６ｃには別のリード線１８ｂを介して他方の外部端子２０ｂが接続される。
【００１６】
なお、この発明は、上述の圧電セラミック振動子１０以外の圧電セラミック振動子、圧電セラミックフィルタおよび圧電セラミック発振子などの他の圧電セラミック素子にも適用される。
【００１７】
【発明の効果】
この発明によれば、ＳｒＢｉ₄ Ｔｉ₄ Ｏ₁₅を主成分とする圧電磁器組成物であって、電気機械結合係数ｋｔが２０％以上に改善されかつ共振周波数の温度変化率が４５以下に改善され、特にたとえば圧電セラミックフィルタ、圧電セラミック発振子および圧電セラミック振動子などの圧電セラミック素子などの材料として有用な圧電磁器組成物およびそれを用いた圧電セラミック素子が得られる。
【図面の簡単な説明】
【図１】この発明にかかる圧電セラミック振動子の一例を示す斜視図である。
【図２】図１に示す圧電セラミック振動子の断面図解図である。
【符号の説明】
１０ 圧電セラミック振動子
１２ 圧電磁器
１２ａ、１２ｂ 圧電磁器層
１４ａ、１４ｂ、１４ｃ 振動電極
１６ａ、１６ｂ、１６ｃ 引出電極
１８ａ、１８ｂ リード線
２０ａ、２０ｂ 外部端子[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric ceramic composition and a piezoelectric ceramic element using the same, and in particular, a piezoelectric ceramic composition useful as a material for a piezoelectric ceramic element such as a piezoelectric ceramic filter, a piezoelectric ceramic oscillator and a piezoelectric ceramic vibrator, and the like. The present invention relates to a piezoelectric ceramic element using the.
[0002]
[Prior art]
As a piezoelectric ceramic composition used for piezoelectric ceramic elements such as piezoelectric ceramic filters, piezoelectric ceramic resonators and piezoelectric ceramic vibrators, lead zirconate titanate (Pb (Ti _x Zr _1-x ) O ₃ ) or titanic acid has heretofore been used. Piezoelectric ceramic compositions mainly composed of lead (PbTiO ₃ ) are widely used. However, a piezoelectric ceramic composition mainly composed of lead zirconate titanate or lead titanate contains a large amount of lead in the composition, so that the uniformity of the product is reduced due to evaporation of lead oxide in the manufacturing process. There was a problem to do. In order to prevent deterioration of product uniformity due to evaporation of lead oxide during the manufacturing process, a piezoelectric ceramic composition containing no lead or only a small amount in the composition is preferable.
In contrast, a piezoelectric ceramic composition mainly composed of a bismuth layered compound such as SrBi ₄ Ti ₄ O ₁₅ does not contain lead oxide in the composition, and thus the above-described problems do not occur.
[0003]
[Problems to be solved by the invention]
However, in a piezoelectric ceramic composition mainly composed of SrBi ₄ Ti ₄ O ₁₅ or the like, lead zirconate titanate conventionally used in piezoelectric ceramic elements such as piezoelectric ceramic filters, piezoelectric ceramic oscillators and piezoelectric ceramic vibrators. Or, compared with a piezoelectric ceramic composition containing lead titanate as a main component, the electromechanical coupling coefficient kt is small and the temperature change rate frTC at a resonance frequency of −20 ° C. to 80 ° C. shown below is large. It has not been done.
frTC = (fr (max) −fr (min)) / (fr (20 ° C.) · 100)
fr (max): highest resonance frequency in the temperature range of −20 ° C. to 80 ° C. fr (min): lowest resonance frequency in the temperature range of −20 ° C. to 80 ° C. fr (20 ° C.): resonance frequency at 20 ° C. [0004]
Therefore, the main object of the present invention is to improve the electromechanical coupling coefficient kt of the piezoelectric ceramic composition mainly composed of SrBi ₄ Ti ₄ O ₁₅ and the temperature change rate frTC of the resonance frequency from −20 ° C. to 80 ° C. Piezoelectric ceramic filters, piezoelectric ceramic resonators, piezoelectric ceramic resonators, and other piezoelectric ceramic elements that exhibit electromechanical coupling coefficient kt (20% or higher) and a temperature change rate frTC (45 or lower) of a resonant frequency that can be put to practical use A piezoelectric ceramic composition useful as a material and a piezoelectric ceramic element using the same are provided.
[0005]
[Means for Solving the Problems]
The piezoelectric ceramic composition according to this invention, in the piezoelectric ceramic composition comprising a main component represented by the general formula SrBi ₄ Ti ₄ O _15, represented at least one of Sc and Y in the general formula A piezoelectric ceramic composition characterized by containing 0.1 mol or less (excluding 0) with respect to 1 mol of Bi in the main component.
In the piezoelectric ceramic composition according to the present invention, Mn may be contained in an amount of 1.5% by weight or less (excluding 0) in terms of MnCO ₃ .
The piezoelectric ceramic element according to the present invention is a piezoelectric ceramic element including a piezoelectric ceramic made of the piezoelectric ceramic composition according to the present invention and an electrode formed on the piezoelectric ceramic.
The main component in the piezoelectric ceramic composition according to the present invention is represented by the general formula SrBi ₄ Ti ₄ O ₁₅ , but the molar ratio of each element may be slightly different.
[0006]
In the piezoelectric ceramic composition according to the present invention, the content of Sc and Y is 0.1 mol or less (excluding 0) with respect to Bi and 1 mol. This is because a practical electromechanical coupling coefficient kt cannot be obtained, or a polarizable porcelain cannot be obtained.
Takahashi et al., In Japanese Patent Application No. 48-85292, contains 0.005 to 0.7% by weight of Mn in terms of MnO in a piezoelectric ceramic composition mainly composed of SrBi ₄ Ti ₄ O _15. The electromechanical coupling coefficient kt has been clarified by the above, but even in such a piezoelectric ceramic composition, that is, in a piezoelectric ceramic composition containing an appropriate amount of Mn in the piezoelectric ceramic composition as the main component, The effect is effective, and a useful piezoelectric ceramic composition having a larger electromechanical coupling coefficient kt and a small temperature change rate frTC of the resonance frequency can be obtained.
In the invention according to claim 2 , if the content of Mn is 1.5% by weight or less (not including 0) in terms of MnCO ₃ , a polarizable porcelain cannot be obtained if the content is higher than this. Because.
In addition, when Y is selected from the elements contained in Sc and Y, in addition to the improvement of the electromechanical coupling coefficient kt, the temperature change rate frTC of the resonance frequency is particularly small. Piezoelectric ceramic compositions more useful as materials for piezoelectric ceramic elements such as oscillators and piezoelectric ceramic vibrators can be obtained.
[0007]
The above object, other objects, features, and advantages of the present invention will become more apparent from the following detailed description of the embodiments of the present invention with reference to the drawings.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
(Example)
First, SrCO ₃ , Bi ₂ O ₃ , TiO ₂ , Sc ₂ O ₃ , Y ₂ O _3, and MnCO ₃ are prepared as starting materials, and these are composed (Sr _1-x M _x ) Bi ₄ Ti ₄ O _15. + Y wt% MnCO ₃ (M is either Sc or Y. 0 ≦ x ≦ 0.45, 0 ≦ y ≦ 1.6.) Wet using a ball mill for about 4 hours Mixed to obtain a mixture. The obtained mixture was dried and calcined at 700 to 900 ° C. to obtain a calcined product. Then, after roughly pulverizing the calcined product, an appropriate amount of an organic binder was added and wet pulverized for 4 hours using a ball mill, and the particle size was adjusted through a 40-mesh sieve. Next, this was molded into a disc having a diameter of 12.5 mm and a thickness of 2 mm at a pressure of 1000 kg / cm ² , and this was fired at 1150 to 1250 ° C. in the atmosphere to obtain a disc-shaped porcelain. . After applying a silver paste on the surface (both main surfaces) of this porcelain and baking it to form a silver electrode, a DC voltage of 5 to 10 kV / mm in an insulating oil at 150 to 200 ° C. is applied to 10 to 30. The piezoelectric ceramic (sample) was obtained by applying a polarization treatment for a minute.
And about the obtained sample, the electromechanical coupling coefficient kt and the temperature change rate frTC of the resonant frequency were measured. The results are shown in Table 1. Table 1 also shows the element symbol of M and the numerical values of x and y in the composition of each sample. In Table 1, it should be noted that ¼ of x in the above composition formula, that is, x / 4 corresponds to the content (mol) of M with respect to Bi and 1 mol.
[0009]
[Table 1]

The * mark in the sample number column indicates that the sample is outside the scope of the present invention.
[0010]
As shown in Table 1, all the samples according to the examples of the present invention are in practical use with an electromechanical coupling coefficient kt of 20% or more and a temperature change rate frTC of resonance frequency of 45 or less. Therefore, it is apparent that the piezoelectric ceramic composition is particularly useful as a material for piezoelectric ceramic elements such as piezoelectric ceramic filters, piezoelectric ceramic oscillators, and piezoelectric ceramic vibrators.
As shown in Table 1, when Y is included, that is, in Samples Nos. 2, 3 and 5 of the embodiments of the present invention, a useful piezoelectric ceramic having a particularly small temperature change rate frTC of the resonance frequency is obtained. It is clear.
[0011]
The piezoelectric ceramic composition according to the present invention is not limited to the compositions of the above-described examples, and is effective within the scope of the gist of the invention.
[0012]
In the above-described embodiment, the electromechanical coupling coefficient kt and the temperature change rate frTC of the resonance frequency are examples of the longitudinal vibration of the disk-shaped piezoelectric ceramic vibrator. However, the effect of the present invention is disk-shaped. The piezoelectric ceramic vibrator is not limited to the thickness longitudinal vibration, and other vibrations used for other piezoelectric ceramic elements, such as piezoelectric ceramic filters and piezoelectric ceramic oscillators, such as thickness shear vibration and harmonics of thickness longitudinal vibration. The mode is also effective as in the case of thickness longitudinal vibration.
[0013]
FIG. 1 is a perspective view showing an example of a piezoelectric ceramic vibrator according to the present invention, and FIG. A piezoelectric ceramic vibrator 10 shown in FIGS. 1 and 2 includes, for example, a rectangular parallelepiped piezoelectric ceramic 12. The piezoelectric ceramic 12 includes two piezoelectric ceramic layers 12a and 12b. These piezoelectric ceramic layers 12a and 12b are made of the above-described piezoelectric ceramic composition according to the present invention, and are laminated and integrally formed. Further, these piezoelectric ceramic layers 12a and 12b are polarized in the same thickness direction as indicated by arrows in FIG.
[0014]
Between the piezoelectric ceramic layers 12a and 12b, for example, a circular vibrating electrode 14a is formed at the center, and for example, a T-shaped lead electrode 16a is formed from the vibrating electrode 14a to one end face of the piezoelectric ceramic 12. Further, on the surface of the piezoelectric ceramic layer 12a, for example, a circular vibrating electrode 14b is formed at the center, and for example, a T-shaped lead electrode 16b is formed from the vibrating electrode 14b to the other end face of the piezoelectric ceramic 12. Further, on the surface of the piezoelectric ceramic layer 12b, for example, a circular vibrating electrode 14c is formed at the center thereof, and for example, a T-shaped extraction electrode 16c is formed from the vibrating electrode 14c to the other end surface of the piezoelectric ceramic 12.
[0015]
One external terminal 20a is connected to the lead electrode 16a via a lead wire 18a, and the other external terminal 20b is connected to the lead electrodes 16b and 16c via another lead wire 18b.
[0016]
The present invention is also applicable to other piezoelectric ceramic elements such as piezoelectric ceramic vibrators, piezoelectric ceramic filters, and piezoelectric ceramic oscillators other than the piezoelectric ceramic vibrator 10 described above.
[0017]
【The invention's effect】
According to the present invention, a piezoelectric ceramic composition containing SrBi ₄ Ti ₄ O ₁₅ as a main component, the electromechanical coupling coefficient kt is improved to 20% or more, and the temperature change rate of the resonance frequency is improved to 45 or less. In particular, a piezoelectric ceramic composition useful as a material for a piezoelectric ceramic element such as a piezoelectric ceramic filter, a piezoelectric ceramic oscillator and a piezoelectric ceramic vibrator, and a piezoelectric ceramic element using the same are obtained.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an example of a piezoelectric ceramic vibrator according to the present invention.
FIG. 2 is a cross-sectional schematic view of the piezoelectric ceramic vibrator shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Piezoelectric ceramic vibrator | oscillator 12 Piezoelectric ceramic 12a, 12b Piezoelectric ceramic layers 14a, 14b, 14c Vibration electrode 16a, 16b, 16c Lead electrode 18a, 18b Lead wire 20a, 20b External terminal

Claims (3)

General formula SrBi _Four Ti _Four O ₁₅ In the piezoelectric ceramic composition composed of the main component represented by the formula: A piezoelectric ceramic composition comprising: Mn to MnCO _Three The piezoelectric ceramic composition according to claim 1, wherein the piezoelectric ceramic composition is contained in an amount of 1.5% by weight or less (excluding 0). A piezoelectric ceramic comprising the piezoelectric ceramic composition according to claim 1 or 2, and
A piezoelectric ceramic element including an electrode formed on the piezoelectric ceramic.

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