JPH01236666A - Polarization of piezoelectric ceramic - Google Patents

Abstract

PURPOSE:To dispense with the addition of polarizing electrodes to a piezoelectric ceramic layer by a method wherein polarization is accomplished by applying an electric potential across conductive elastomer layers sandwiching a piezoelectric ceramic layer. CONSTITUTION:A piezoelectric ceramic layer 1 is sandwiched between conductive elastomer layers 2, and the resultant laminate is further sandwiched between brass plates 3. Then the entirety is tightly packed under two brass leaf springs 4. The assembly is as is placed in silicone oil, an electric potential is applied across the brass leaf springs 4, which polarizes the piezoelectric ceramic layer 1. With the conductive elastomer layers 2 serving as electrodes and the piezoelectric ceramic layer 1 being thus polarized, there is no need for the addition of polarizing electrodes to the piezoelectric ceramic layer 1, which reduces the cost.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of polarizing piezoelectric ceramics that function as a filter or an oscillator in an electric circuit.

(Prior Art) In recent years, with the increase in the amount of information, information processing speed has been increased, and the demand for filters and oscillators has increased, as well as the trend toward higher frequencies. 10-1 using piezoelectric ceramics
For a piezoelectric resonator in the 00100O band, it is advantageous to utilize its thickness longitudinal vibration. A method of manufacturing a piezoelectric resonator using this thickness longitudinal vibration has conventionally been shown in FIG. 2. That is, approximately 100 mm thicker than the intended thickness of the piezoelectric resonator.
- Decentralization electrode 1 on a fairly thick plate-shaped piezoelectric ceramic 11
2 is applied, and a potential difference is applied between both polarization electrodes 12 to polarize the piezoelectric ceramic 11. Further, both sides of the piezoelectric ceramic 11 were polished to remove the polarization electrode 12 and at the same time, the desired thickness was obtained, and then electrodes for the piezoelectric resonator were applied by vapor deposition or the like.

(Problems to be Solved by the Invention) In the above conventional method, it is necessary to provide one polarization electrode, and this polarization electrode is unnecessary on the product.
This was one of the factors that made the cost high.

An object of the present invention is to eliminate the conventional drawbacks and provide a piezoelectric resonator that utilizes thickness longitudinal vibration at low cost.

(Means for Solving the Problems) The piezoelectric ceramic polarization method of the present invention involves sandwiching the piezoelectric ceramic between conductive elastomers in the thickness direction and polarizing the piezoelectric ceramic by applying a potential difference between the conductive elastomers. It is something.

(Function) According to the method of the present invention, there is no need to provide polarization electrodes to piezoelectric ceramics, and the cost can be significantly reduced.

(Example) An embodiment of the present invention will be described based on FIG.

FIG. 1 is a sectional view showing the method of polarizing piezoelectric ceramics of the present invention. In this example, P bT 103-
P b Z r O3P b(Mgl/3 Nb2/3
) An experiment was conducted using a three-component piezoelectric ceramic of 0:+. In Figure 1, length 3 cs, width 2a
1. A piezoelectric ceramic 1 with a thickness of about 400 μm is sandwiched in the thickness direction between carbon composite conductive elastomer 2 with a thickness of 5 m, which is further sandwiched between brass plates 3 with a thickness of 2 mm. This is a brass leaf spring 4 with a thickness of 0.5 an.
The entire scissor was placed in close contact between the two. In this state, soak the brass plate in silicone oil heated to 100℃ and remove the brass plate.
A potential difference of 2 kV was applied between the conductive elastomers 2 through the conductive elastomers 2 to polarize the piezoelectric ceramics 1. After that, the piezoelectric ceramic 1 was made with particle size #20 so that the thickness was 250 mm.
Both sides were polished using No. 00 abrasive and cut into 5+Mn squares. Silver electrodes with a diameter of 2 m were deposited at the center of both surfaces perpendicular to the thickness of the obtained piezoelectric ceramic of 5 x 5 x 0.25 mm to obtain a piezoelectric resonator utilizing longitudinal vibration of the thickness. The table below shows a comparison of the electrical characteristics obtained from this piezoelectric resonator and the electrical characteristics obtained from a piezoelectric resonator obtained by a conventional method.

However, K: Electromechanical coupling coefficient Nt: Frequency constant ε/ε. : Relative dielectric constant In the table, ε/ε. The measurement is 5x5x0.2
It was determined using a piezoelectric resonator in which silver electrodes were deposited on both surfaces of a 5 m piezoelectric ceramic plate perpendicular to the thickness direction.

As described above, in this example, piezoelectric ceramics are sandwiched between conductive elastomers and polarized by applying a voltage difference between the conductive elastomers, so that the conductive elastomers act as electrodes and no electrodes for polarization are provided. In both cases, polarization can be achieved in the same way as when polarization electrodes are provided, so the cost can be significantly reduced.

This conductive elastomer works as an electrode because it is highly elastic and can adhere closely along the surface of the piezoelectric ceramic.

Metals with a high elastic modulus are not suitable because they do not adhere sufficiently to the piezoelectric ceramics. Furthermore, even when a conductive elastomer is used, if it is thin, adhesion may deteriorate when the surface of the piezoelectric ceramic has large irregularities, so the thicker the conductive elastomer, the better.
A sufficient effect can be expected if the thickness is 2 mm or more. In addition, it is also affected by the warpage and surface roughness of the piezoelectric ceramics, so it is desirable that the warpage and surface roughness of the piezoelectric ceramics be as small as possible.

Although a carbon composite conductive elastomer was used in this example, other conductive elastomers may be used. In this example, PbTi0. -PbZrO, -Pb(Mgl/
Although the 3Nb2/3)O system was used, it is also effective for other piezoelectric ceramics.

(Effects of the Invention) According to the present invention, a piezoelectric ceramic is sandwiched between conductive elastomers in the thickness direction, and by applying a potential difference between the conductive elastomers, the conductive elastomer acts as an electrode, and the piezoelectric ceramic is polarized. Therefore, there is no need to add polarization electrodes to piezoelectric ceramics,
The JJx value can be greatly reduced, and its practical effect is great.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a method for polarizing piezoelectric ceramics according to an embodiment of the present invention, and FIG. 2 is a sectional view showing a conventional method for polarizing piezoelectric ceramics. 1... Piezoelectric ceramics, 2... Conductive elastomer, 3... Brass plate, 4... Leaf spring. Patent applicant: Matsushita Electric Industrial Co., Ltd. Figure 1 Figure 2

Claims (1)

[Claims] A method for polarizing piezoelectric ceramics, which comprises sandwiching piezoelectric ceramics between conductive elastomers in the thickness direction and applying an electric field to the piezoelectric ceramics by applying a potential difference between the conductive elastomers.