JP4247936B2 - Piezoelectric ceramic composition - Google Patents

Description

【００１５】
表１より、機械的品質係数Ｑｍは、Ｘ＝０.３で最大値８６１を得ており、（Ｂｉ_０．５Ｎａ_０．５）ＴｉＯ_３に対しＱｍの改善が計られている。
【００１６】
しかし、Ｘが０.１未満及び０.５を超える範囲では、Ｑｍが３００以下と非常に小さく実用化は難しい。また、Ｘが０.１〜０.５の範囲では、電気機械結合係数も減少しておらず、実用に適している事が判った。
【００１７】
以上より、組成式（Ｂｉ_０．５Ｎａ_０．５）ＴｉＯ_３にＢｉＦｅＯ_３を１０〜５０％固溶させることにより、（Ｂｉ_０．５Ｎａ_０．５）ＴｉＯ_３の電気機械結合係数を劣化させることなく、機械的品質係数Ｑｍを向上させることができる。これにより、フィルター、振動子等の用途への適用が可能となる。
【００１８】
【発明の効果】
以上、述べたように、本発明によれば、組成式が（１−Ｘ）（Ｂｉ_0.5Ｎａ_0.5）ＴｉＯ₃−ＸＢｉＦｅＯ₃であって、Ｘが０.１＜Ｘ≦０.５の範囲である無鉛の圧電体磁器組成物を提供することで、酸化鉛による大気汚染がない材料によるフィルター、振動子等の用途への適用が期待できる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a composition of a piezoelectric material used for wave devices, sensors, actuators and the like.
[0002]
[Prior art]
Conventionally, piezoelectric As the ceramic material consists of bicomponent _PZT (PbTiO 3 -PbZrO ₃₎ ceramics and, PCM consists of three components _{[PbTiO 3 -PbZrO 3 -Pb (Mg} 0.5 Nb 0.5 ) TiO ₃ ] based ceramics have been mainly used.
[0003]
The reason for this is that the above materials exhibit large piezoelectricity, and furthermore, by adjusting the proportion of each component amount of these materials, it is possible to meet the required characteristics of various applications such as sensors, actuators, filters, etc. It is.
[0004]
[Problems to be solved by the invention]
However, all of these materials are mainly composed of lead, and about 2/3 by weight is lead oxide. Lead oxide has high volatility even at low temperatures, and may leak into the atmosphere during production such as calcination and sintering, and may be eluted from industrial waste. Be careful as a harmful substance that pollutes the environment. There is a need. Also, enormous costs must be invested in installing pollution prevention equipment, and there is a great demand for lead-free material development from the economical aspect.
[0005]
In addition, in the existing lead-free piezoelectric material composition formula (Bi _0.5 Na _0.5 ) TiO ₃ , the value of the mechanical quality factor Qm is low, and considering applications such as filters and vibrators that require high Qm It is difficult to apply this material.
[0006]
That is, an object of the present invention is to provide a piezoelectric ceramic composition that does not contain lead oxide and has a high mechanical quality factor Qm that can be used for applications such as filters and vibrators.
[0007]
[Means for Solving the Problems]
The present invention has a composition formula (1-X) (Bi _0.5 Na _0.5 ) TiO ₃ —XBiFeO ₃ ( 0.1 <X ≦ 0.5 ), does not contain lead, and has a high mechanical quality factor Qm. It is a piezoelectric ceramic composition.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be specifically described.
[0009]
Bismuth oxide (Bi ₂ O ₃ ), sodium carbonate (Na ₂ CO ₃ ), titanium oxide (TiO ₂ ), and iron oxide (Fe ₂ O ₃ ) were used as the main component materials. A predetermined amount of these were weighed and mixed in ethanol for 20 hours by a ball mill using zirconia balls. This was kept at 800 ° C. for 1 hour and calcined, and further pulverized with a ball mill for 10 hours.
[0010]
It was granulated using polyvinyl alcohol as a binder, and pressure-molded into a disk shape having a diameter of 20 mm and a thickness of 1 mm at a pressure of 1 ton / cm ² . The molded sample was baked at a temperature of 1050 to 1150 ° C. for 2 hours.
[0011]
Silver electrodes were provided on both surfaces of the sintered body, and a DC voltage of 4 kV / mm was applied between the electrodes in 100 ° C. silicon oil to polarize in the thickness direction.
[0012]
Then, the piezoelectric and dielectric properties of these samples were measured. In the piezoelectric measurement, an electromechanical coupling coefficient and a mechanical quality coefficient were calculated by a resonance-antiresonance method using an LF impedance analyzer. In addition, the dielectric characteristics were measured at a measurement frequency of 1 MHz using an LCR meter.
[0013]
Table 1 shows an electrical machine in a piezoelectric ceramic composition having a composition formula of (1-X) (Bi _0.5 Na _0.5 ) TiO ₃ —XBiFeO ₃ and having a range of 0 ≦ X ≦ 0.6. coupling coefficient _{k 33, k p,} showing a _{k t,} the mechanical quality factor Qm, and the dielectric constant ε ₃₃ ^t / ε _0.
[0014]
[Table 1]

[0015]
From Table 1, the mechanical quality factor Qm has a maximum value 861 at X = 0.3, and an improvement in Qm is measured with respect to (Bi _0.5 Na _0.5 ) TiO ₃ .
[0016]
However, in the range where X is less than 0.1 and exceeds 0.5, Qm is very small as 300 or less, and practical application is difficult. In addition, it was found that when X is in the range of 0.1 to 0.5, the electromechanical coupling coefficient is not decreased and is suitable for practical use.
[0017]
From the above, the electromechanical coupling coefficient of (Bi _0.5 Na _0.5 ) TiO ₃ is deteriorated by dissolving 10-50% of BiFeO ₃ in the composition formula (Bi _0.5 Na _0.5 ) TiO _3. The mechanical quality factor Qm can be improved without making it. This makes it possible to apply to uses such as filters and vibrators.
[0018]
【The invention's effect】
As described above, according to the present invention, the composition formula is (1-X) (Bi _0.5 Na _0.5 ) TiO ₃ —XBiFeO ₃ , and X is in the range of 0.1 <X ≦ 0.5 . By providing a certain lead-free piezoelectric ceramic composition, it can be expected to be applied to applications such as filters and vibrators made of materials free from air pollution by lead oxide.

Claims (1)

A piezoelectric ceramic composition having a composition formula of (1-X) (Bi _0.5 Na _0.5 ) TiO ₃ —XBiFeO ₃ , wherein X is in a range of 0.1 <X ≦ 0.5 .