JP2000272963A - Piezoelectric porcelain composition - Google Patents

Abstract

(57) [Problem] To provide a piezoelectric ceramic composition containing no lead oxide and having a high mechanical quality factor Qm that can be practically used for applications such as filters and vibrators. SOLUTION: The composition formula is (1-X) (Bi _0.5 Na).
_0.5) A _{TiO 3} -XBiFeO 3, X is 0.
A piezoelectric ceramic composition represented by 1 ≦ X ≦ 0.5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a composition of a piezoelectric material used for a wave device, a sensor, an actuator and the like.

[0002]

2. Description of the Related Art Conventionally, piezoelectric ceramic materials include:
Composed of two-component _PZT (PbTiO 3 -PbZrO
₃ ) PCM [P
_{bTiO 3 -PbZrO 3 -Pb (Mg 0.5} Nb
_0.5 ) TiO ₃ ] -based ceramics have been mainly used.

[0003] The reason is that the above-mentioned materials exhibit large piezoelectricity, and furthermore, by adjusting the ratio of the amount of each component of the materials, the characteristics required for various uses such as sensors, actuators, and filters can be satisfied. Because it can be.

[0004]

However, all of these materials are mainly composed of lead and have a weight ratio of about 2/3.
Is lead oxide. Lead oxide has high volatility even at low temperatures, and may be leaked into the air during calcination or sintering, or may be eluted from industrial waste. There is a need. In addition, enormous costs must be invested in the installation of pollution prevention equipment, and there is a great demand for the development of lead-free materials in terms of economy.

[0005] In addition, the composition formula (Bi
_0.5 Na _0.5 ) TiO ₃ has a mechanical quality factor Qm
Is low, it is difficult to apply this material in consideration of applications such as filters and vibrators that require a high Qm.

That is, an object of the present invention is to contain no lead oxide,
Another object of the present invention is to provide a piezoelectric ceramic composition having a high mechanical quality factor Qm that can be practically used for a filter, a vibrator or the like.

[0007]

According to the present invention, there is provided a composition of formula (1-
_{X) (Bi 0.5 Na 0.5)} TiO 3 -XBiFeO
₃ (0.1 ≦ X ≦ 0.5), which is a piezoelectric ceramic composition containing no lead and having a high mechanical quality factor Qm.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below.

Bismuth oxide (Bi ₂
O ₃ ), sodium carbonate (Na ₂ CO ₃ ), titanium oxide (TiO ₂ ), and iron oxide (Fe ₂ O ₃ ). These were weighed in predetermined amounts and mixed in ethanol for 20 hours in a ball mill using zirconia balls. This is 80
Hold at 0 ° C for 1 hour, calcine, and further ball mill for 10 hours.
Milling was carried out for hours.

Polyvinyl alcohol as a binder
And granulated at a pressure of 1 ton / cm. ²With a diameter of 20m
It was press-formed into a disk having a thickness of 1 mm and a thickness of 1 mm. Molded sample
Is fired for 2 hours at a temperature of 1050 to 1150 ° C.
Was.

A silver electrode is provided on both sides of this sintered body,
A DC voltage of 4 kV / mm was applied between the electrodes in silicone oil at ℃ to polarize in the thickness direction.

Then, for these samples, piezoelectric,
The dielectric properties 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. The dielectric characteristics were measured using an LCR meter at a measurement frequency of 1 MHz.
Was measured.

Table 1 shows that the composition formula is (1-X) (Bi_0.5
Na_0.5) TiO₃-XBiFeO₃Where 0 ≦
Electric machine in a piezoelectric porcelain composition in the range of X ≦ 0.6
Mechanical coupling coefficient k₃₃, K_p, K_t, Mechanical quality factor Qm,
And relative permittivity ε₃₃ ^t/ Ε ₀Is shown.

[0014]

[Table 1]

[0015] From Table 1, the mechanical quality factor Qm is expressed as X =
A maximum value of 861 was obtained at 0.3, and (Bi _0.5 Na
_0.5 ) An improvement in Qm over TiO ₃ has been measured.

However, when X is less than 0.1 and more than 0.5, Qm is extremely small at 300 or less, and practical use is difficult. Further, when X was in the range of 0.1 to 0.5, the electromechanical coupling coefficient was not reduced, and it was found that the electromechanical coupling coefficient was suitable for practical use.

From the above, the composition formula (Bi _0.5 N
a _0.5) by solid solution BiFeO ₃ 10 to 50% in _{TiO 3, (Bi 0.5 Na 0.5} ) TiO 3
The mechanical quality coefficient Qm can be improved without deteriorating the electromechanical coupling coefficient. This enables application to applications such as filters and vibrators.

[0018]

As described above, according to the present invention,
When the composition formula is (1-X) (Bi_0.5Na _0.5) TiO
_3-XBiFeO₃Wherein X is 0.1 ≦ X ≦ 0.5.
By providing a lead-free piezoelectric ceramic composition that is in the range,
Filters and filters made of materials that do not cause air pollution by lead oxide
It can be expected to be used for applications such as moving elements.

Claims (1)

[Claims] A composition formula (1-X) (Bi _0.5 Na
_0.5) A _{TiO 3} -XBiFeO 3, X is 0.
A piezoelectric porcelain composition, wherein 1 ≦ X ≦ 0.5.