JPS628960B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a porcelain piezoelectric material, which can constitute an energy-containing resonator for thick vertical vibrations, has a large mechanical quality factor _QM , and can be processed into a thin plate. The present invention aims to provide a porcelain piezoelectric material. As the use of ICs in high-frequency circuits such as television receivers progresses, there are strong expectations that the peripheral components of IC circuits, especially reactance circuits, will be solid-state, non-adjustable, and high-performance. When using a piezoelectric ceramic as a high-frequency resonator, it is advantageous to use thickness vibration, particularly thickness vertical vibration, in which the resonant frequency is determined by the thickness. In the case of thick vertical vibration, the frequency constant is 2000Hz. About m, if
In order to use it at a resonant frequency of 50MHz, it must be made into a very thin plate of about 40μm.
When using thick vertical vibration in resonators, filters, etc., an important issue is the removal of unnecessary resonance. The energy confinement method is effective for removing unnecessary vibrations. In order for this energy confinement method to be applicable to the fundamental wave resonance of the thickness vertical vibration, the Poisson's ratio σ _t must be larger than 1/3. σ _t is (2-C ^D ₃₃・S ^D ₄₄ )/(2-2C ^D ₃₃・S ^E _4
4 ) is given by. However, C ^D ₃₃ is elastic stiffness related to thickness vertical vibration, and S ^E ₄₄ is elastic compliance related to thickness shear vibration. Furthermore, in order to obtain a resonator with low loss in a high frequency region, it is necessary that the mechanical quality factor Q _M be 300 or more. Conventional firing methods yield only mechanically weak materials and can only be polished to a depth of about 100 to 200 μm.
Even in the case of vertical vibration, a resonator with a frequency of 10 to 20 MHz was the limit that could be constructed using these ceramics. Until now, there have been few examples of measurement of σ _t .
The composition range with σ _t of 1/3 or more has not been clarified. And if Q _M is 300 or more, and σ _t is
Up to now, no material has been available that can be processed into thin plates with a thickness of 1/3 or more. The present invention has σ _t of 1/3 or more and Q _M of 300 or more.
This relates to a method for obtaining high-frequency electromagnetic materials that can be processed into thin plates of approximately 30 μm.
−z) [xPb(Mg1/3Nb2/3)O ₃ +(1−x−y)
PbTiO ₃ +yPbZrO ₃ ] +zCoO (however, 0.025≦x
≦0.125, 0.372≦y≦0.618, 0.004≦z≦0.020)
This is based on the discovery that it can be obtained by hot-pressing a material having the following composition under limited conditions. The following is a description based on examples. Raw materials of PbO, MgO, Nb ₂ O ₅ , TiO ₂ , ZrO ₂ and CoO were weighed to have the composition shown in the table below and mixed in a ball mill. After passing it and drying it at 850℃,
It was calcined for 2 hours. After calcining, it was ground in a ball mill, molded, and then hot pressed. For comparison, a molded body made under the same conditions was normally fired. The fired samples were polished to a minimum thickness of 30 μm. The mechanically weak sample cracked by the time it reached 30 μm. The relationship between firing conditions and polishing limits is shown in the table below.

[Table] In normal firing, a sample with a high density was obtained even under the conditions shown in the table above, but it was difficult to polish the sample to a thickness of 200 μm or less. Hot pressing allows obtaining extremely thin samples. According to the inventors' experimental results, the temperature of the hot press is
Even when the temperature was 1050 to 1250°C, polishing up to 30 μm was possible. If the pressing force was less than 100 Kg/cm ² , hot pressing would result in insufficient sintering and only non-uniform samples could be obtained. By hot pressing at a pressure in the range of 150 to 500 kg/cm ² , a sample that could be polished to a thickness of 30 μm was obtained.
Therefore, the range of hot press conditions in the method of the present invention is a temperature of 1050 to 1250°C and a pressure of 150 to 500°C.
Kg/ ^cm2 is desirable. Regarding the hot press time, if it is too short (less than 30 minutes), sintering will be insufficient.
Actually, it may be within a range of 1 to 5 hours. Figure 1 shows a sample hot pressed at 1100℃ for 2 hours and 300Kg/ ^cm2 (x=0.063, z=0.008).
An example of the change of σ _t with respect to y is shown below. As is clear from the figure, σ _t reaches a maximum at y=0.50.
This tendency does not change depending on the x, z values and hot press conditions. In this sample, the range that satisfies the energy confinement condition of the fundamental wave of the thick vibration, that is, the condition of σ _t >1/3, is 0.44≦y≦0.58. For the sample with x=0.025, 0.478≦y≦0.618
And for the sample with x=0.125, 0.378≦y≦
As a result of experiments, it was confirmed that the condition of σ _t >1/3 was satisfied at 0.518. Figure 2 shows 1100℃, 2 hours, and 300Kg/cm ²
Sample hot pressed under the conditions (x=0.063, y
An example of the change in Q _M with respect to z (=0.50) is shown below.
Q _M reaches its maximum when z is 0.012. This tendency is x,
y, does not change depending on hot press conditions. Second
From the figure, the range of z for Q _M > 300 is 0.004 to 0.020.
It is.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the relationship between the composition of a sample made by the method according to the present invention and Poisson's ratio σ, and FIG. 2 is a diagram showing an example of the relationship between the composition and the mechanical quality factor Q _M It is.

Claims (1)

[Claims] 1 (1-z) [xPb(Mg1/3Nb2/3)O ₃ +(1-
x-y) PbTiO ₃ +yPbZrO ₃ ]+zCoO, 0.025≦x≦0.125, 0.372≦y≦
A method for producing a porcelain piezoelectric material, which comprises hot pressing a composition in the range of 0.618, 0.004≦z≦0.020 at a temperature of 1050 to 1250°C and a pressure of 150 to 500 Kg/cm ² .