JP2004107141A - Piezoelectric ceramic composition and piezoelectric device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein improvement of the temperature characteristic of resonant frequency is associated with deterioration in the oscillation characteristic when constructing a piezoelectric device which utilizes a third harmonic wave of thickness longitudinal mode using lead titanate piezoelectric ceramic composition. <P>SOLUTION: A piezoelectric substrate 3 established in a piezo-resonator 1 is composed using the lead titanate piezoelectric ceramic composition represented by the formula: ABO<SB>3</SB>which contains Pb, La and Sr in a site A and Ti and Mn in a site B. The piezoelectric ceramic composition contains 40.0-41.7 mol% PbO, 51.9-53.6 mol% TiO<SB>2</SB>, 0.3-3.6 mol% SrO, 4.0-6.1 mol% La<SB>2</SB>O<SB>3</SB>and SrO in total and 0.5-1.2 mol% MnO<SB>2</SB>. <P>COPYRIGHT: (C)2004,JPO

Description

【００３５】
表１において、試料番号に＊を付したものはこの発明の範囲外の比較例である。
【００３６】
表１を参照して、「Ｐｂ」が４０．０モル％以上かつ４１．７モル％以下、「Ｓｒ＋Ｌａ」が４．０モル％以上かつ６．１モル％以下、「Ｓｒ」が０．３モル％以上かつ３．６モル％以下、「Ｔｉ」が５１．９モル％以上かつ５３．６モル％以下、および「Ｍｎ」が０．５モル％以上かつ１．２モル％以下の条件をすべて満足する試料２〜５、８〜１１、１８および１９によれば、「ｆｒの最大変化率」の絶対値が０．１０％以下というように、共振周波数の温度特性が良好であり、また、「３ｒｄθｍａｘ」が８３．０度以上というように、良好な発振特性を示している。また、「Ｑｍ」が３５００以上というように、高い値を示している。
【００３７】
これらに対して、「Ｐｂ」が４０．０モル％より少ないと、たとえば試料１からわかるように、「ｆｒの最大変化率」の絶対値が０．１０％より大きくなり、共振周波数の温度特性が悪化している。他方、「Ｐｂ」が４１．７モル％より多いと、たとえば試料６からわかるように、「３ｒｄθｍａｘ」が８３．０度より小さく、発振特性が低下し、また、「Ｑｍ」が３５００より小さくなってしまう。
【００３８】
また、「Ｓｒ＋Ｌａ」が４．０モル％より少ないと、たとえば試料７からわかるように、Ｑｍが３５００より低下している。他方、「Ｓｒ＋Ｌａ」が６．１モル％を超えると、たとえば試料１２からわかるように、「ｆｒの最大変化率」の絶対値が０．１０％より大きくなり、共振周波数の温度特性が悪化している。
【００３９】
また、「Ｓｒ」が０．３モル％未満であると、たとえば試料１３からわかるように、「３ｒｄθｍａｘ」が８３．０度より小さくなり、発振特性が低下し、また、「Ｑｍ」が３５００より低くなっている。他方、「Ｓｒ」が３．６モル％を超えると、たとえば試料１４からわかるように、「３ｒｄθｍａｘ」が８３．０度より小さくなり、発振特性が低下し、また、「Ｑｍ」が３５００より低くなっている。
【００４０】
また、「Ｔｉ」については、試料１５のように、５１．９モル％未満であると、たとえば試料１６からわかるように、「３ｒｄθｍａｘ」が８３．０度より小さくなり、発振特性が低下し、また、「Ｑｍ」が３５００より低くなっている。他方、
５３．６モル％を超えると、「ｆｒの最大変化率」の絶対値が０．１０％より大きくなり、共振周波数の温度特性が悪化している。
【００４１】
また、「Ｍｎ」が０．４モル％未満であると、たとえば試料１７からわかるように、「３ｒｄθｍａｘ」が８３．０度より小さくなり、発振特性が低下している。これは、「Ｍｎ」の含有量が少なく、そのため、焼結不足を招いたためである。他方、「Ｍｎ」が１．３モル％を超えると、たとえば試料２０からわかるように、絶縁抵抗が低下し、分極が不十分となり、「ｆｒの最大変化率」、「３ｒｄθｍａｘ」および「Ｑｍ」を測定することが不可能であった。
【００４２】
なお、以上説明した実験例では、出発原料として、前述したように、酸化鉛、酸化チタン、酸化ランタン、炭酸ストロンチウムおよび炭酸マンガンをそれぞれ用いたが、焼成により酸化物を生成する物質であれば、どのような化合物を用いてもよい。
【００４３】
また、仮焼粉末の成形方法としては、加圧成形以外の成形方法が適用されてもよい。
【００４４】
【発明の効果】
以上のように、この発明に係るチタン酸鉛系圧電磁器組成物によれば、これを用いて圧電デバイスを構成したとき、この圧電デバイスの共振周波数の温度特性を向上させることができるとともに、発振特性をも向上させることができる。
【図面の簡単な説明】
【図１】この発明による圧電磁器組成物を用いて構成される圧電デバイスの一例としての圧電共振子１を示す断面図である。
【図２】図１に示した圧電共振子１に備える圧電共振素子２を単独で示す斜視図である。
【符号の説明】
１　圧電共振子
２　圧電共振素子
３　圧電基板
４，５　励振電極[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a piezoelectric ceramic composition and a piezoelectric device configured using the same. In particular, the present invention relates to a piezoelectric ceramic composition having good temperature characteristics of resonance frequency and exhibiting high oscillation characteristics when used for an oscillator, and a piezoelectric device formed using the same.
[0002]
[Prior art]
As a material of a piezoelectric device such as a piezoelectric vibrator or a piezoelectric resonator, a piezoelectric ceramic mainly containing titanium-lead zirconate (PZT) or lead titanate (PT) is widely used at present. Of these, many of the oscillators in the 10 to 80 MHz band use the third harmonic of the thickness longitudinal vibration of a piezoelectric ceramic mainly composed of PT.
[0003]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 03-060463 [Patent Document 2]
JP-A-63-151667
[Problems to be solved by the invention]
The above-described oscillator using the third harmonic of the thickness longitudinal vibration of the piezoelectric ceramic mainly composed of PT has a large change in the resonance frequency with respect to the temperature. For example, −40 ° C. based on room temperature (20 ° C.) The temperature change rate at 125 ° C. is 0.10% or more in absolute value.
[0005]
In order to reduce the temperature change rate of the resonance frequency, the PT-based piezoelectric ceramic composition represented by general formula ABO _3, such as the two substituents or the B-site element the A-site element to another element, Various countermeasures have been attempted.
[0006]
However, when the temperature change rate of the resonance frequency is reduced, the oscillation characteristics are deteriorated. Therefore, a piezoelectric ceramic composition satisfying both the temperature characteristics and the oscillation characteristics of the resonance frequency has not been obtained at present.
[0007]
Accordingly, an object of the present invention is to provide a piezoelectric ceramic composition which can satisfy both the temperature characteristics and the oscillation characteristics of the resonance frequency as described above, and a piezoelectric device using the same.
[0008]
[Means for Solving the Problems]
The present invention is represented by general formula ABO _3, the A site contains Pb, La and Sr, the B site containing Ti and Mn, be those directed first to the lead titanate-based piezoelectric ceramic composition In order to solve the above technical problem, the present invention is characterized by having the following configuration.
[0009]
That is, the piezoelectric ceramic composition according to the present invention contains 40.0 mol% or more and 41.7 mol% or less of Pb in terms of PbO, and 51.9 mols of Ti in terms of TiO _2. % To 53.6 mol%, Sr is converted to SrO, and 0.3 mol% to 3.6 mol% is included. La is converted to La ₂ O ₃ and converted to SrO. And 4.0 mol% or more and 6.1 mol% or less in total with
It is characterized in that Mn is contained in an amount of 0.5 mol% or more and 1.2 mol% or less in terms of MnO ₂ .
[0010]
The present invention is also directed to a piezoelectric device configured using the piezoelectric ceramic composition as described above.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a sectional view showing a piezoelectric resonator as an example of a piezoelectric device constituted by using the piezoelectric ceramic composition according to the present invention. The piezoelectric resonator 1 shown in FIG. 1 is configured using an energy trap type piezoelectric resonance element 2 using a thickness longitudinal vibration mode. FIG. 2 is a perspective view of the piezoelectric resonance element 2 shown in FIG.
[0012]
The piezoelectric resonance element 2 includes a rectangular piezoelectric substrate 3. A first excitation electrode 4 is formed at the center of the upper surface of the piezoelectric substrate 3, while a second excitation electrode 5 is formed at the center of the lower surface of the piezoelectric substrate 3, and these first and second excitation electrodes 4 are formed. 5 are positioned so as to face each other. In the illustrated embodiment, the excitation electrodes 4 and 5 are circular, but may be changed to other shapes such as a rectangle.
[0013]
The excitation electrodes 4 and 5 are connected to extraction electrodes 6 and 7, respectively. The extraction electrode 6 is extended to one edge on the upper surface of the piezoelectric substrate 3, while the extraction electrode 7 is extended to the other edge on the lower surface of the piezoelectric substrate 3.
[0014]
Sealing substrates 8 and 9 are arranged above and below the piezoelectric resonance element 2, respectively, and are joined to the piezoelectric substrate 3 via an insulating adhesive (not shown). The sealing substrates 8 and 9 are made of an insulator or a dielectric. A recess 10 is provided on the lower surface of the sealing substrate 8, while a recess 11 is provided on the upper surface of the sealing substrate 9.
[0015]
These concave portions 10 and 11 are for preventing the vibration at the portion where the excitation electrodes 4 and 5 face each other, that is, at the vibrating portion, so that the presence of the concave portions 10 and 11 causes such vibration. The sealing substrates 8 and 9 are prevented from contacting the portions.
[0016]
On the outer surface of the piezoelectric resonator 1, external electrodes 12 and 13 electrically connected to the extraction electrodes 6 and 7, respectively, are formed.
[0017]
In order to manufacture such a piezoelectric resonator 1, a piezoelectric substrate 3 obtained by firing a lead titanate-based piezoelectric ceramic composition, which will be described in detail later, is prepared, and the piezoelectric substrate 3 has a predetermined resonance frequency. Polished uniformly until the thickness becomes vibrating. Next, full-surface electrodes are formed on both main surfaces of the piezoelectric substrate 3, and the piezoelectric substrate 3 on which the full-surface electrodes are formed is polarized. Next, ink is applied in a predetermined pattern on the entire surface electrode, and thereafter, the entire surface electrode is etched in a portion where the ink is not applied, so that the excitation electrodes 4 and 5 having the predetermined pattern and the extraction electrodes 6 and 7 is obtained.
[0018]
Next, the ink is removed with an organic solvent. Next, the sealing substrates 8 and 9 are bonded to the upper and lower sides of the piezoelectric resonance element 2 thus obtained, and then the external electrodes 12 and 13 are formed, whereby the piezoelectric resonator 1 is completed.
[0019]
The piezoelectric substrate 3 provided in the piezoelectric resonator 1 is made of a sintered body of the piezoelectric ceramic composition according to the present invention. The piezoelectric ceramic composition is represented by general formula ABO _3, the A site contains Pb, La and Sr, the B site containing Ti and Mn, a lead-based piezoelectric porcelain composition titanate, It has the following composition.
[0020]
That is, this lead titanate-based piezoelectric ceramic composition contains Pb in an amount of 40.0 mol% or more and 41.7 mol% or less in terms of PbO, and Ti in an amount of 51.9 in terms of TiO _2. wherein mol% or more and 53.6 mol% or less, the Sr, in terms of SrO, comprises more than 0.3 mol% and 3.6 mol% or less, the La, in terms of _La 2 _{O 3,} the SrO It contains 4.0 mol% or more and 6.1 mol% or less in total with the converted Sr, and contains 0.5 mol% or more and 1.2 mol% or less of Mn in terms of MnO ₂ .
[0021]
According to such a piezoelectric ceramic composition, as can be seen from the results of experimental examples described later, preferable characteristics can be obtained with respect to both the temperature characteristics and the oscillation characteristics of the resonance frequency.
[0022]
Next, an experimental example performed to determine the composition range of the piezoelectric ceramic composition according to the present invention will be described.
[0023]
[Experimental example]
Powders of lead oxide (PbO), titanium oxide (TiO ₂ ), lanthanum oxide (La ₂ O ₃ ), strontium carbonate (SrCO ₃ ) and manganese carbonate (MnCO ₃ ) were prepared as starting materials, and these were prepared in a table. It was prepared so as to have the composition ratio shown in FIG. In Table 1, the respective composition ratios of “Pb”, “Sr + La”, “Sr”, “Ti” and “Mn” are respectively calculated as PbO, SrO, La ₂ O ₃ , TiO ₂ and MnO ₂ . Shown in mol%.
[0024]
Next, the above prepared powder was wet-mixed with a media stirring mill, dried, and calcined at a temperature of 800 to 1000 ° C.
[0025]
Next, an appropriate amount of a binder is added to the obtained calcined powder, mixed, dried and pressed, and the obtained molded body is fired in an oxygen atmosphere at a temperature of 1100 to 1300 ° C., A sintered body of the piezoelectric ceramic composition according to each sample was obtained.
[0026]
Next, each sintered body is polished to a thickness of 250 μm, and electrodes having a predetermined shape are formed on both main surfaces thereof as described below. As shown in FIG. Was prepared.
[0027]
First, full-surface electrodes are formed on both main surfaces of the polished sintered body, and an electric field is applied to the polished sintered body on which the full-surface electrodes are formed in oil at 8.0 to 12.0 kV / mm. A voltage was applied to perform polarization processing.
[0028]
Next, the sintered body subjected to the polarization treatment was aged at a temperature of 150 to 250 ° C.
[0029]
Next, on the entire surface electrode of the sintered body, ink is applied in a predetermined pattern, and thereafter, the excitation electrode and the extraction electrode having the predetermined pattern are formed by etching the entire surface electrode in a portion where the ink is not applied. Formed.
[0030]
Further, the ink adhering to the electrodes and the like was removed with an organic solvent to produce a piezoelectric resonator element (test piece).
[0031]
The finally manufactured test piece is a rectangular parallelepiped and has a size of about 6 mm × about 6 mm × 250 μm. The resonance electrode portion has a circular shape of φ1 mm on both main surfaces.
[0032]
For each of the samples thus obtained, the maximum change rate of the resonance frequency (fr) in the temperature range of −40 ° C. to 125 ° C. with reference to room temperature (20 ° C.) is obtained, and the thickness longitudinal vibration around 30 MHz is obtained. The oscillation characteristic of the third harmonic of the mode, that is, the maximum value of the phase angle (3rdθmax) was obtained. Qm was also evaluated for each sample.
[0033]
These results are shown in Table 1.
[0034]
[Table 1]

[0035]
In Table 1, those with * added to the sample numbers are comparative examples outside the scope of the present invention.
[0036]
Referring to Table 1, “Pb” is 40.0 mol% or more and 41.7 mol% or less, “Sr + La” is 4.0 mol% or more and 6.1 mol% or less, and “Sr” is 0.3 mol% or less. Mol% or more and 3.6 mol% or less, "Ti" is 51.9 mol% or more and 53.6 mol% or less, and "Mn" is 0.5 mol% or more and 1.2 mol% or less. According to Samples 2 to 5, 8 to 11, 18, and 19, which satisfy all conditions, the temperature characteristics of the resonance frequency are good such that the absolute value of the “maximum change rate of fr” is 0.10% or less, and , “3rdθmax” is 83.0 degrees or more, indicating good oscillation characteristics. In addition, it shows a high value such as “Qm” of 3500 or more.
[0037]
On the other hand, if “Pb” is less than 40.0 mol%, as can be seen from Sample 1, for example, the absolute value of “the maximum change rate of fr” becomes greater than 0.10%, and the temperature characteristics of the resonance frequency Is getting worse. On the other hand, when “Pb” is more than 41.7 mol%, as can be seen from Sample 6, for example, “3rdθmax” is smaller than 83.0 degrees, the oscillation characteristics are reduced, and “Qm” is smaller than 3500. Would.
[0038]
If “Sr + La” is less than 4.0 mol%, for example, as can be seen from Sample 7, Qm is lower than 3500. On the other hand, if “Sr + La” exceeds 6.1 mol%, the absolute value of “maximum change rate of fr” becomes larger than 0.10%, as can be seen from Sample 12, for example, and the temperature characteristics of the resonance frequency deteriorate. ing.
[0039]
When “Sr” is less than 0.3 mol%, for example, as can be seen from Sample 13, “3rdθmax” is smaller than 83.0 degrees, the oscillation characteristics are reduced, and “Qm” is smaller than 3500. It is lower. On the other hand, when “Sr” exceeds 3.6 mol%, as can be seen from Sample 14, for example, “3rdθmax” becomes smaller than 83.0 degrees, the oscillation characteristics are lowered, and “Qm” is lower than 3500. Has become.
[0040]
When “Ti” is less than 51.9 mol% as in Sample 15, for example, as can be seen from Sample 16, “3rdθmax” is smaller than 83.0 degrees, and the oscillation characteristics are reduced. “Qm” is lower than 3500. On the other hand,
If it exceeds 53.6 mol%, the absolute value of the "maximum change rate of fr" becomes larger than 0.10%, and the temperature characteristic of the resonance frequency is deteriorated.
[0041]
When “Mn” is less than 0.4 mol%, for example, as can be seen from Sample 17, “3rdθmax” is smaller than 83.0 degrees, and the oscillation characteristics are degraded. This is because the content of “Mn” is small, and as a result, insufficient sintering was caused. On the other hand, when “Mn” exceeds 1.3 mol%, as can be seen from the sample 20, for example, the insulation resistance decreases, the polarization becomes insufficient, and the “maximum change rate of fr”, “3rdθmax”, and “Qm” Was impossible to measure.
[0042]
In the experimental examples described above, as described above, as starting materials, lead oxide, titanium oxide, lanthanum oxide, strontium carbonate, and manganese carbonate were used. Any compound may be used.
[0043]
Further, as a method of forming the calcined powder, a forming method other than the pressure forming may be applied.
[0044]
【The invention's effect】
As described above, according to the lead titanate-based piezoelectric ceramic composition of the present invention, when a piezoelectric device is formed using the composition, the temperature characteristics of the resonance frequency of the piezoelectric device can be improved, and oscillation can be achieved. Characteristics can also be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a piezoelectric resonator 1 as an example of a piezoelectric device formed using a piezoelectric ceramic composition according to the present invention.
FIG. 2 is a perspective view showing a piezoelectric resonance element 2 provided in the piezoelectric resonator 1 shown in FIG. 1 alone.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Piezoelectric resonator 2 Piezoelectric resonance element 3 Piezoelectric substrates 4 and 5 Excitation electrodes

Claims (2)

Is represented by general formula ABO _3, the A-site Pb, include La and Sr, the B site containing Ti and Mn, a lead-based piezoelectric porcelain composition titanate,
Containing Pb in an amount of 40.0 mol% or more and 41.7 mol% or less in terms of PbO;
Ti and in terms of TiO _2, contains 51.9 mol% or more and 53.6 mol% or less,
Containing 0.3 mol% or more and 3.6 mol% or less of Sr in terms of SrO;
La contains 4.0 mol% or more and 6.1 mol% or less in total of La and Sr converted to SrO when converted to La ₂ O ₃ ;
A piezoelectric ceramic composition comprising Mn in an amount of 0.5 mol% or more and 1.2 mol% or less in terms of MnO ₂ . A piezoelectric device comprising the piezoelectric ceramic composition according to claim 1.

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