JPH10167821A - Piezoelectric ceramic composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain low firing temp. and to ensure a small grain diameter, denseness, a low dielectric constant and relatively high piezoelectric property by incorporating MgO into Pb(Me1/2 W1/2 )A(Sn1/3 Sb2/3 )BTiCZrDO3 . SOLUTION: A basic compsn. represented by the formula Pb(Me1/2 W1/2 )A(Sn1/3 Sb2/3 )BTiCZrDO3 (where Me is Co, Ni or Mg, 0.01<=A<=0.50, 0.01<=B<=0.25, 0.20<=C<=0.75, 0.56<=D<=0.80 and A+B+C+D=1) is prepd. and 0.02-2.0wt.% MgO and 0.05-5.0wt.% one or more among MnO2 , NiO and Fe2 O3 are incorporated into the basic compsn. Required metal oxides such as PbO, TiO2 , ZrO2 and MgO are weighted and mixed by means of a ball mill so as to satisfy the formula and the resultant mixture is calcined at 700-900 deg.C, pulverized by means of a ball mill, mixed with an aq. PVA soln. and granulated. The resultant granules are press-compacted under 1 ton/cm<2> pressure to form a discoid compact and this compact is fired at 1,000-1,250 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric ceramic composition, and more particularly to a piezoelectric ceramic composition suitable for an oscillator or a surface acoustic wave device in a high frequency range.

[0002]

2. Description of the Related Art Conventionally, as a piezoelectric material, titanium titanate
Or lead zirconate titanate porcelain.
Various improvements have been made depending on the purpose of use. For example, Pb
(Sn _1/3Sb_2/3)_XTi_YZr_ZO_ThreeSystem composition (Sho No. 5
4-32516, Japanese Patent Publication No. 54-36557
Report) has excellent piezoelectric properties and small crystal grain size
And high mechanical strength.
It is a piezoelectric material suitable for use in the region.

[0003]

However, these piezoelectric materials have a high firing temperature of 1200 to 1300 ° C.
Even if a fine particle material is used, the firing temperature is 1100 ° C.
Did not go down. Therefore, the evaporation of lead oxide during firing is remarkably inhibited from densification, and even if sufficient sintering is performed, compositional variation is likely to occur.As a result, the piezoelectric characteristics of porcelain vary, and furthermore, lead oxide A large amount of steam was released into the atmosphere, causing environmental problems.

The present invention solves this problem.
00 ° C. can be fired in the following relatively low temperature, the crystal grain size is small, dense, and the dielectric constant is small, a relatively large piezoelectric oscillator and the surface of the high frequency region having the (K _t and Q _m is greater) It is an object of the present invention to provide a piezoelectric ceramic composition effective for a wave element.

[0005]

[MEANS FOR SOLVING THE PROBLEMS]
The piezoelectric ceramic composition of the present invention comprises Pb (Me_1/2W_1/2) _A
(Sn_1/3Sb_2/3)_BTi_CZr_DO_Three(However, Me is Co,
Any one of Ni and Mg, and 0.01 ≦ A ≦ 0.
50, 0.01 ≦ B ≦ 0.25, 0.20 ≦ C ≦ 0.7
5, 0.56 ≦ D ≦ 0.80, A + B + C + D = 1)
In the basic composition shown, MgO was added as an auxiliary component in an amount of 0.02.
~ 2.0% by weight of MnO_Two, NiO
And Fe_TwoO_Three0.05 to 5.0 weight of at least one of
%.

[0006] With the above structure, it can be fired at a low temperature, has a small crystal grain size, is dense, has a small dielectric constant, and has a large piezoelectricity.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is directed to Pb (Me _1/2 W _1/2 ) _A (Sn _1/3 Sb _2/3 ) _B Ti _C
Zr _D O ₃ (where Me is any one of Co, Ni and Mg, and A, B, C and D each represent 0.01 ≦ A ≦
0.50, 0.01 ≦ B ≦ 0.25, 0.20 ≦ C ≦
0.75, 0.56 ≦ D ≦ 0.80, A + B + C + D =
Which sinters at a relatively low temperature of 1200 ° C. or lower and has a crystal grain size of 0.02 to 2.0% by weight of MgO as an auxiliary component. It is small, dense, has a small dielectric constant, and has relatively large piezoelectricity.

[0008] The second aspect of the present invention is to provide a second aspect,
And MnO_Two, NiO and Fe_TwoO _ThreeAt least one of
Of 0.05 to 5.0% by weight.
To improve the bondability, polarization characteristics, temperature characteristics and aging characteristics.
Can be.

In the basic composition of the piezoelectric ceramic composition of the present invention, 0.01 ≦ A ≦ 0.50, 0.01 ≦ B ≦ 0.25,
The reason for limiting the values to 0.20 ≦ C ≦ 0.75 and 0.56 ≦ D ≦ 0.80 is that sintering is difficult or the piezoelectricity is significantly reduced outside this range. Lead-based composite perovskite type Pb (Me _1/2 W _1/2 ) O ₃ and Pb (S
Both n _1/3 Sb _2/3 ) O ₃ act as a mineralizer and have the effect of lowering the firing temperature of the porcelain to obtain a uniform sintered body, but A <0.01 or B In the case of <0.01, such an effect is negligible. A
> Reduction of K _p and K _t is significantly in the case of 0.50 or B> 0.25.

[0010] MgO as an auxiliary component in the basic composition is 0.0
By adding 2 to 2.0% by weight, the firing temperature of the composition can be lowered and at the same time, crystal grain growth can be suppressed. Further, it is possible to improve MnO _2, NiO and Fe ₂ O at least one further sinterability by incorporating added 0.05 to 5.0 wt% of _3, polarization characteristics, temperature characteristics and aging characteristics.

Hereinafter, specific embodiments of the present invention will be described. PbO, TiO ₂ , ZrO ₂ , S
nO ₂ , Sb ₂ O ₃ , CoO, NiO, MgO, WO ₃ , M
nO ₂ , NiO and Fe ₂ O ₃ were accurately weighed to have the compositions shown in (Table 1) and (Table 2) and mixed well by a ball mill. Then, the mixture was calcined at a temperature of 700 to 900 ° C., and further pulverized by a ball mill. After drying, an aqueous solution of polyvinyl alcohol as a binder was added, and the mixture was granulated, followed by pressure molding at a pressure of 1 ton / cm ² , and
A disk-shaped molded product of 0φ-1t was obtained. The molded body obtained here was fired in a closed furnace at a temperature of 1000 to 1250 ° C. for 1 hour.

After measuring the porcelain density ρ by the Archimedes method, EMAS-60 is used to measure the radial vibration piezoelectric characteristics.
A disc-shaped sample of 16φ-1.0t was prepared according to No. 01, silver electrodes were baked on both sides, and in 100 ° C. silicone oil,
After applying a DC electric field of 3 kV / mm for 30 minutes and polarizing, the dielectric constant ε ^T ₃₃ / ε ₀ , the electromechanical coupling coefficient K _{p in} the spreading direction and the mechanical quality coefficient Q _m were measured. The measurement results are porcelain firing temperature (density maximum), with a particle size G _s average crystal (Table 3) are summarized in (Table 4). From this, the second subcomponent MgO
It can be seen that the addition of C reduces the firing temperature by 20 to 60 ° C. and at the same time reduces the crystal grain size by 50% or more.
EMA to measure the piezoelectric properties of thickness longitudinal vibration
According to S-6003, a disk sample of 10φ-1.0t was prepared, silver electrodes were baked on both sides, and a DC electric field of 3 kV / mm
After polarization by applying for 30 minutes in silicone oil at 00 ° C., the electromechanical coupling coefficient K _t in the thickness direction was measured,
This is also described in (Table 3) and (Table 4). Samples of these samples 4, Sample 5, Sample 6, to obtain the results shown in Figure 1 was measured values of the thickness direction of the electro-mechanical coupling coefficient K _t for samples 1 and 3 due to the polarization temperature. In FIG. 1, a curve a indicates the case of the sample 4, a curve b indicates the case of the sample 5, a curve c indicates the case of the sample 6, a curve d indicates the case of the sample 1, and a curve e.
Indicates the case of sample 3. The embodiment of the present invention employs Mn.
It can be seen that the addition of O ₂ , NiO and Fe ₂ O ₃ facilitates polarization.

Further, when the frequency constant N _t (Hz · m) of the same sample in the longitudinal direction of thickness was determined, the result shown in FIG. 2 was obtained. In FIG. 2, curve a shows the case of sample 4, curve b shows the case of sample 5, curve c shows the case of sample 6, and curve d
Represents the case of sample 1, and curve e represents the case of sample 3. Mn
It can be seen that the addition of O ₂ , NiO and Fe ₂ O ₃ improves the aging characteristics.

Further, the same ceramic resonator as described above is used.
When the temperature characteristics and the aging characteristics of the resonance frequency were measured,
The results shown in (Table 5) were obtained. MnO_Two, NiO and F
e_TwoO _ThreeTemperature characteristics and aging characteristics
It can be seen that the properties are improved.

[0015] Additionally Q _m by the addition of auxiliary components it can be seen that remarkably improved.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

[Table 3]

[0019]

[Table 4]

[0020]

[Table 5]

[0021]

As apparent from the above embodiments, the piezoelectric ceramic composition of the present invention has a low firing temperature, a small crystal grain size, a high density, a small dielectric constant, and a relatively large piezoelectric property. (K _t and Q _m is greater) indicates, is useful as a piezoelectric material for oscillator or surface acoustic wave device of a high-frequency region.

[Brief description of the drawings]

FIG. 1 is a graph _showing the relationship between the polarization temperature and the electromechanical coupling coefficient Kt.

FIG. 2 is a relationship curve diagram of time and a frequency constant N _t (Hz · m).

Claims (2)

[Claims] 1. Pb (Me _1/2 W _1/2 ) _A (Sn _1/3 Sb
_2/3 ) _B Ti _C Zr _D O ₃ (Me is Co, Ni, Mg
A, B, C, and D are each 0.
01 ≦ A ≦ 0.50, 0.01 ≦ B ≦ 0.25, 0.2
0 ≦ C ≦ 0.75, 0.56 ≦ D ≦ 0.80, A + B +
A piezoelectric ceramic composition comprising a basic composition represented by the following formula (C + D = 1) and containing 0.02 to 2.0% by weight of MgO as an auxiliary component. 2. The piezoelectric ceramic composition according to claim 1, further comprising 0.05 to 5.0% by weight of at least one of MnO ₂ , NiO and Fe ₂ O ₃ as a second auxiliary component.