JP2004352544A - Piezoelectric ceramic composition and piezoelectric device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a piezoelectric ceramic composition having both of satisfied heat resistance and oscillation characteristic, and to provide a piezoelectric device using the same. <P>SOLUTION: The lead titanate based piezoelectric ceramic composition constituting a piezoelectric substrate 3 provided, for example, in a piezo-oscillator 1 is expressed by the formula ABO<SB>3</SB>wherein A site contains Pb, Ba and Ce and B site contains Ti and Mn, and contains 40.2 to 4i.9 mol% PbO, 50.9 to 52.5 mol% TiO<SB>2</SB>, 1.9 to 5.5 mol% BaO, 4.9 to 7.1 mol% in total of Ce<SB>2</SB>O<SB>3</SB>and BaO and 0.6 to 1.2 mol% MnO<SB>2</SB>. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００３７】
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。
【００３８】
表１を参照して、「Ｐｂ」が４０．２モル％以上かつ４１．９モル％以下、「Ｂａ＋Ｃｅ」が４．９モル％以上かつ７．１モル％以下、「Ｂａ」が１．９モル％以上かつ５．５モル％以下、「Ｔｉ」が５０．９モル％以上かつ５２．５モル％以下、および「Ｍｎ」が０．６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、８〜１３、１６、２１および２２によれば、「耐熱性」の絶対値が０．１０％以下と良好であり、また、「３ｒｄθｍａｘ」が８４．０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４０００以上というように、高い値を示している。
【００３９】
これらに対して、「Ｐｂ」が４０．２モル％より少ないと、たとえば試料１からわかるように、「耐熱性」の絶対値が０．１０％より大きくなってしまう。他方、「Ｐｂ」が４１．９モル％より多いと、たとえば試料６からわかるように、「３ｒｄθｍａｘ」が８４．０度より小さく、発振特性が低下し、また、「Ｑｍ」が４０００より小さくなってしまう。
【００４０】
また、「Ｂａ＋Ｃｅ」が４．９モル％より少ないと、たとえば試料７からわかるように、「３ｒｄθｍａｘ」が８４．０度より小さく、発振特性が低下し、また、Ｑｍが４０００より小さくなってしまう。他方、「Ｂａ＋Ｃｅ」が７．１モル％を超えると、たとえば試料１４からわかるように、「３ｒｄθｍａｘ」が８４．０度より小さく、発振特性が低下している。
【００４１】
また、「Ｂａ」が１．９モル％未満であると、たとえば試料１５からわかるように、「３ｒｄθｍａｘ」が８４．０度より小さくなり、発振特性が低下し、また、「Ｑｍ」が４０００より低くなっている。他方、「Ｂａ」が５．５モル％を超えると、たとえば試料１７からわかるように、「３ｒｄθｍａｘ」が８４．０度より小さくなり、発振特性が低下し、また、「Ｑｍ」が４０００より低くなっている。
【００４２】
また、「Ｔｉ」が５０．９モル％未満であると、たとえば試料１８からわかるように、「３ｒｄθｍａｘ」が８４．０度より小さくなり、発振特性が低下し、また、「Ｑｍ」が４０００より低くなっている。他方、５２．５モル％を超えると、たとえば試料１９からわかるように、「耐熱性」の絶対値が０．１０％より大きくなってしまう。
【００４３】
また、「Ｍｎ」が０．６モル％未満であると、たとえば試料２０からわかるように、「３ｒｄθｍａｘ」が８４．０度より小さくなり、発振特性が低下し、また、「Ｑｍ」が４０００より低くなっている。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１．２モル％を超えると、たとえば試料２３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、「耐熱性」、「３ｒｄθｍａｘ」および「Ｑｍ」を測定することが不可能であった。
【００４４】
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、酸化セリウム、炭酸バリウムおよび炭酸マンガンをそれぞれ用いたが、仮焼および焼成により酸化物を生成する物質であれば、本実施例で用いた出発原料に限定されることはなく、どのような化合物を用いてもよい。
【００４５】
また、出発原料及び圧電発振素子の作製工程において混入が避けられない物質、例えばＦｅ，Ｃｏ，Ｓｉ，及びＡｌが、本実施例に係る圧電発振素子に混在することがあっても、数百ｐｐｍ程度の不純物レベルならば本実施例と同等の特性を有することが可能である。
【００４６】
また、実施例では圧電共振素子を作製する際に、粉末を加圧成形して成形体を得る方法を用いているが、この方法に限定されることはなく、シート成形・押出成形・鋳込成形などによる方法を用いてもよい。
【００４７】
【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耐熱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発振子１を示す断面図である。
【図２】図１に示した圧電発振子１に備える圧電発振素子２を単独で示す斜視図である。
【符号の説明】
１ 圧電発振子
２ 圧電発振素子
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, when used in an oscillator, heat resistance, for example, a good change rate of the resonance frequency before and after solder reflow treatment, and exhibit high oscillation characteristics, a piezoelectric ceramic composition and a piezoelectric constituted using the same It is about devices.
[0002]
[Prior art]
As a material of a piezoelectric device such as a piezoelectric vibrator or a piezoelectric oscillator, 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]
Oscillator that uses third harmonic of thickness longitudinal vibration of piezoelectric ceramic mainly composed of PT has heat resistance (change of resonance frequency before and after solder reflow processing) when exposed to high temperature of 240 ° C or more in solder reflow processing. Ratio) is as large as 0.2% or more in absolute value.
[0004]
Therefore, this in order to improve the heat resistance, 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 measures Attempted.
[0005]
For example, Patent Document 1, the PT-based piezoelectric ceramic composition represented by the general formula ABO _3, the piezoelectric ceramic composition when allowed to replace other to La elements Pb element mainly composed of A-site element is disclosed Have been.
[0006]
Patent Documents 2 and ₃ disclose that in a PT-based piezoelectric ceramic composition represented by the general formula ABO3, at least one of Sr, Ca, and Ba in addition to the Pb element as a main component is used as an A-site element. A piezoelectric ceramic composition in which the metal element and the Ce element are replaced and the B-site element is replaced with at least one metal element of Ti, Mn, or Al, Fe, Co, Ni, Si, Mg, or Cr Is disclosed.
[0007]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 03-060463 [Patent Document 2]
JP-A-63-151667 [Patent Document 3]
JP-A-63-166756
[Problems to be solved by the invention]
However, in the case of using a piezoelectric ceramic composition as described in Patent Documents 1 to 3 described above, although heat resistance can be improved, oscillation characteristics are deteriorated. A piezoelectric ceramic composition that satisfies both oscillation characteristics has not been obtained.
[0009]
Therefore, an object of the present invention is to provide a piezoelectric ceramic composition which can satisfy both the above-described heat resistance and oscillation characteristics, and a piezoelectric device using the same.
[0010]
[Means for Solving the Problems]
The present invention is directed to a lead titanate-based piezoelectric ceramic composition represented by the general formula ABO _{3 wherein} the A site contains Pb, Ba and Ce, and the B site contains Ti and Mn. In order to solve the above technical problem, the present invention is characterized by having the following configuration.
[0011]
That is, the piezoelectric ceramic composition according to the present invention contains 40.2 mol% or more and 41.9 mol% or less of Pb in terms of PbO, and 50.9 mol% of Ti in terms of TiO _2. wherein% or more and 52.5 mol%, the Ba, in terms of BaO, including 1.9 mol% or more and 5.5 mol% or less, a Ce, in terms of _Ce 2 _{O 3,} converted to BaO And 4.9 mol% or more and 7.1 mol% or less in total, and Mn contains 0.6 mol% or more and 1.2 mol% or less in terms of MnO _2. And
[0012]
The present invention is also directed to a piezoelectric device configured using the piezoelectric ceramic composition as described above.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a cross-sectional view showing a piezoelectric oscillator as an example of a piezoelectric device formed using the piezoelectric ceramic composition according to the present invention. The piezoelectric oscillator 1 shown in FIG. 1 is configured using an energy trap type piezoelectric oscillation element 2 utilizing a thickness longitudinal vibration mode. FIG. 2 is a perspective view of the piezoelectric oscillation element 2 shown in FIG.
[0014]
The piezoelectric oscillation 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.
[0015]
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.
[0016]
Sealing substrates 8 and 9 are arranged above and below the piezoelectric oscillation 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.
[0017]
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.
[0018]
On the outer surface of the piezoelectric oscillator 1, external electrodes 12 and 13 that are electrically connected to the extraction electrodes 6 and 7, respectively, are formed.
[0019]
In order to manufacture such a piezoelectric oscillator 1, a piezoelectric substrate 3 obtained by firing a lead titanate-based piezoelectric ceramic composition, which will be described in detail later, is prepared. This 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, 7 is obtained.
[0020]
Next, the ink is removed by an organic solvent. Further, the sealing substrates 8 and 9 are bonded to the upper and lower sides of the piezoelectric oscillation element 2 thus obtained, and then the external electrodes 12 and 13 are formed, whereby the piezoelectric oscillator 1 is completed.
[0021]
The piezoelectric substrate 3 provided in the piezoelectric oscillator 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 include Pb, Ba and Ce, the B site containing Ti and Mn, a lead-based piezoelectric porcelain composition titanate, It has the following composition.
[0022]
That is, the lead titanate-based piezoelectric ceramic composition, a Pb, in terms of PbO, contains 40.2 mol% or more and 41.9 mol%, a Ti, in terms of TiO _2, 50.9 wherein mol% or more and 52.5 mol%, the Ba, in terms of BaO, including 1.9 mol% or more and 5.5 mol% or less, a Ce, in terms of _Ce 2 _{O 3,} the BaO It contains 4.9 mol% or more and 7.1 mol% or less in total with converted Ba, and Mn contains 0.6 mol% or more and 1.2 mol% or less in terms of MnO ₂ .
[0023]
According to such a piezoelectric ceramic composition, as can be seen from the results of the experimental examples described later, it is possible to obtain favorable characteristics in both heat resistance and oscillation characteristics.
[0024]
Next, an experimental example performed to determine the composition range of the piezoelectric ceramic composition according to the present invention will be described.
[0025]
[Experimental example]
Powders of lead oxide (PbO), titanium oxide (TiO ₂ ), cerium oxide (Ce ₂ O ₃ ), barium carbonate (BaCO 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”, “Ba + Ce”, “Ba”, “Ti” and “Mn” are respectively calculated as PbO, BaO, Ce ₂ O ₃ , TiO ₂ and MnO ₂ . Shown in mol%.
[0026]
Next, the above prepared powder was wet-mixed with a media stirring mill, dried, and calcined at a temperature of 800 to 1000 ° C.
[0027]
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.
[0028]
Next, each sintered body is polished to a thickness of 250 μm, electrodes having a predetermined shape are formed on both main surfaces thereof as described below, and a piezoelectric oscillation element as shown in FIG. Produced.
[0029]
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.
[0030]
Next, the polarized sintered body was aged at 150 ° C. However, the temperature of the aging step after polarization may be in the range of 150 ° C to 250 ° C.
[0031]
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.
[0032]
Further, the ink adhering to the electrodes and the like was removed with an organic solvent to produce a piezoelectric oscillation element (test piece).
[0033]
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.
[0034]
For each of the samples thus obtained, the oscillation characteristics of the third harmonic in the thickness longitudinal vibration mode near 30 MHz, that is, the maximum value of the phase angle (3rdθmax) and the heat resistance were determined. Here, [heat resistance] = {[resonance frequency before reflow treatment] − [resonance frequency before reflow treatment]} / [resonance frequency before reflow treatment] × 100 (%). Qm was also evaluated for each sample.
[0035]
These results are shown in Table 1.
[0036]
[Table 1]

[0037]
In Table 1, those with * added to the sample numbers are comparative examples outside the scope of the present invention.
[0038]
Referring to Table 1, "Pb" is 40.2 mol% or more and 41.9 mol% or less, "Ba + Ce" is 4.9 mol% or more and 7.1 mol% or less, and "Ba" is 1.9 mol%. Mol% or more and 5.5 mol% or less, "Ti" is 50.9 mol% or more and 52.5 mol% or less, and "Mn" is 0.6 mol% or more and 1.2 mol% or less. According to Samples 2 to 5, 8 to 13, 16, 21 and 22 that satisfy all conditions, the absolute value of “heat resistance” is as good as 0.10% or less, and the “3rdθmax” is 84.0 degrees or more. Thus, good oscillation characteristics are shown. Also, a high value such as “Qm” of 4000 or more is shown.
[0039]
On the other hand, if “Pb” is less than 40.2 mol%, the absolute value of “heat resistance” becomes greater than 0.10%, for example, as can be seen from Sample 1. On the other hand, when “Pb” is more than 41.9 mol%, as can be seen from Sample 6, for example, “3rdθmax” is smaller than 84.0 degrees, the oscillation characteristics are reduced, and “Qm” is smaller than 4000. Would.
[0040]
If “Ba + Ce” is less than 4.9 mol%, for example, as can be seen from Sample 7, “3rdθmax” is smaller than 84.0 degrees, the oscillation characteristics are reduced, and Qm is smaller than 4000. . On the other hand, when “Ba + Ce” exceeds 7.1 mol%, “3rdθmax” is smaller than 84.0 degrees, as can be seen from Sample 14, for example, and the oscillation characteristics are degraded.
[0041]
If “Ba” is less than 1.9 mol%, as can be seen from Sample 15, for example, “3rdθmax” becomes smaller than 84.0 degrees, the oscillation characteristics deteriorate, and “Qm” becomes larger than 4000. It is lower. On the other hand, if “Ba” exceeds 5.5 mol%, as can be seen from Sample 17, for example, “3rdθmax” becomes smaller than 84.0 degrees, the oscillation characteristics deteriorate, and “Qm” becomes lower than 4000. Has become.
[0042]
If “Ti” is less than 50.9 mol%, for example, as can be seen from Sample 18, “3rdθmax” is smaller than 84.0 degrees, the oscillation characteristics are reduced, and “Qm” is smaller than 4000. It is lower. On the other hand, if it exceeds 52.5 mol%, as can be seen from Sample 19, for example, the absolute value of “heat resistance” becomes larger than 0.10%.
[0043]
When “Mn” is less than 0.6 mol%, as can be seen from Sample 20, for example, “3rdθmax” becomes smaller than 84.0 degrees, the oscillation characteristics deteriorate, and “Qm” becomes larger than 4000. It is lower. This is because the content of “Mn” is small, and as a result, insufficient sintering was caused. On the other hand, when “Mn” exceeds 1.2 mol%, as can be seen, for example, from Sample 23, the insulation resistance decreases and the polarization becomes insufficient, and “heat resistance”, “3rdθmax” and “Qm” are measured. It was impossible.
[0044]
In the experimental examples described above, lead oxide, titanium oxide, cerium oxide, barium carbonate, and manganese carbonate were used as the starting materials, respectively, as described above. If so, the starting material used in this example is not limited, and any compound may be used.
[0045]
In addition, even if starting materials and substances that cannot be avoided in the manufacturing process of the piezoelectric oscillation element, such as Fe, Co, Si, and Al, may be mixed in the piezoelectric oscillation element according to the present embodiment, several hundred ppm may be used. If the impurity level is on the order, it is possible to have the same characteristics as those of this embodiment.
[0046]
Further, in the embodiment, when manufacturing the piezoelectric resonance element, a method of obtaining a molded body by press-molding powder is used, but the method is not limited to this method, and sheet molding, extrusion molding, and casting are performed. A method such as molding may be used.
[0047]
【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 heat resistance of the piezoelectric device can be improved and the oscillation characteristics can be improved. Can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a piezoelectric oscillator 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 oscillation element 2 included in the piezoelectric oscillator 1 shown in FIG. 1 alone.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Piezoelectric oscillator 2 Piezoelectric oscillator 3 Piezoelectric substrates 4 and 5 Excitation electrodes

Claims (2)

Is represented by general formula ABO _3, the A-site include Pb, Ba and Ce, the B site containing Ti and Mn, a lead titanate-based piezoelectric ceramic composition,
Containing Pb in an amount of 40.2 mol% or more and 41.9 mol% or less in terms of PbO;
The Ti, in terms of TiO _2, contains 50.9 mol% or more and 52.5 mol% or less,
Ba is contained in an amount of 1.9 mol% or more and 5.5 mol% or less in terms of BaO,
Ce is included in an amount of 4.9 mol% or more and 7.1 mol% or less in total with Ba converted to CeO when converted to Ce ₂ O ₃ ,
A piezoelectric ceramic composition comprising Mn in an amount of 0.6 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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