JPH05267744A - Polarization of piezoelectric ceramic - Google Patents

Abstract

PURPOSE:To contrive the simplification of the manufacturing process of a piezoelectric ceramic and a reduction of an electrode material by a method wherein a plurality of pieces of thin plate-shaped piezoelectric ceramic materials are superposed on each other in the thickness direction of the ceramic materials to form an aggregate, conductive members are respectively pressed on both surfaces, which oppose to each other in parallel to the thickness direction of the aggregate, of the aggregate and a high voltage is applied to the conductive members. CONSTITUTION:A plurality of sheets of thin plate-shaped piezoelectric ceramic materials 1 are superposed on each other in the thickness direction of the ceramic materials to form an aggregate, conductive rubbers 2, which are used as conductive members and are made of silicon, are respectively applied to both surfaces, which correspond to the end surfaces to oppose to each other of the ceramic material of one sheet of the ceramic materials, of the aggregate to install one pair of copper plates 3 on the rubbers and the copper plates 3 are pressed by a spring 4. The plates 3 are made to closely adhere to the rubbers 2 by the spring 4 and the rubbers 2 are made to closely adhere to the ceramic materials 1 and discharge a role to work as electrodes for polarization. This aggregate is put in a silicone oil and a high voltage of 15kV, for example, is applied to the conductive rubbers 2 to polarize. Thereby, the conventional process for the formation of the electrodes for polarization use and the removal of the electrodes becomes unnecessary, a shortening of the manufacturing process of the piezoelectric ceramic aggregate is contrived and a reduction of a high-cost noble metal electrode material is also contrived.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a ceramic filter,
The present invention relates to a method for polarizing a piezoelectric ceramic used as a piezoelectric vibrator that utilizes thickness shear vibration in a ceramic oscillator or the like.

[0002]

2. Description of the Related Art Piezoelectric ceramics have been developed steadily by utilizing various unique electric-mechanical energy conversion functions and various kinds of applied devices have been developed due to the variety of performances and variety of applications.

Piezoelectric ceramics are basically manufactured by the same manufacturing method as ordinary ceramics, but differ from other ceramics in that there is an important step called "polarization" for imparting piezoelectric activity.

As a method of polarization, as described in Hiroshi Izumi, "Electronic Ceramics", pages 72-73 (published by Seibundou Shinkosha Co., Ltd. in 1990), piezoelectric ceramics are made to have conductivity such as silver. Of the electrode material and applying a high voltage such as 3 kV / mm at 100 ° C. to the electrode in insulating oil. FIG. 3 shows an example of the polarization process. In FIG. 3, 11 is a piezoelectric ceramic block, 1
2 is an electrode provided on both sides of the piezoelectric ceramic block 11,
Reference numeral 13 is a copper plate serving as a base plate, 14 is a lead wire, 15 is a constant temperature oil tank, 16 is silicon oil as insulating oil, 17 is a high voltage power source for applying a high voltage, and 18 is a protective resistor.

A conventional piezoelectric vibrator utilizing thickness-shear vibration (hereinafter referred to as a thickness-shear vibrator) has been manufactured through the following polarization process. In FIG. 3, first, a piezoelectric ceramic block 11 having electrodes 12 formed by coating and baking an electrode material such as silver on both opposing planes is attached to a copper plate
One of the electrodes 12 is placed in close contact therewith. Next electrode 1
The lead wire 14 is connected to the other of the two and the copper plate 13, and the piezoelectric ceramic block 11 and the copper plate 13 are connected to the constant temperature oil tank 15
Of the lead wire 14 is directly connected to the high-voltage power supply 17 through the protective resistor 18. Then, for example, a high voltage is applied at 100 ° C. for polarization.

Next, after the electrodes 12 of the piezoelectric ceramic block 11 thus polarized are removed, the piezoelectric ceramic block 11 shown in FIG.
As shown in the perspective view showing the cutting step, the thin plate is processed in a direction parallel to the polarization direction A by a slice processing method or the like.
Then, an electrode for excitation such as silver is formed on a surface parallel to the polarization direction A of the thin plate-shaped piezoelectric ceramics by a method such as a vacuum vapor deposition method that does not raise the temperature to form a thickness sliding oscillator. .

[0007]

However, in the case of the thickness sliding oscillator, after the polarization, the electrode used for the polarization is removed, and then, as shown in FIG. However, the electrode material such as silver and the piezoelectric ceramic, which are expensive after polarization, are discarded by polishing or slicing, which is wasteful.

It is an object of the present invention to provide a thin plate-shaped piezoelectric ceramics polarization method capable of performing polarization without forming unnecessary electrodes after polarization.

[0009]

In order to achieve this object, the polarization method of the first invention of the present invention is a method in which a plurality of thin plate-shaped piezoelectric ceramics are aligned in the thickness direction and stacked.
A conductive member having plasticity is pressed against both opposing surfaces parallel to the thickness direction, and a high voltage is applied and polarization is performed without electrodes.

According to the second aspect of the polarization method of the present invention, a plurality of thin plate-shaped piezoelectric ceramics are aligned and stacked in the thickness direction, and then sandwiched on both sides by dummy blocks made of the same material as the piezoelectric ceramics. As in the first aspect of the invention, a conductive member having plasticity is pressed against the electrode, and a high voltage is applied with no electrode to perform polarization.

[0011]

In the first aspect of the present invention, the conductive member having plasticity is brought into close contact with the end face of a plurality of thin plate-shaped piezoelectric ceramics arranged, and the specific resistance of the conductive member is sufficiently smaller than that of the piezoelectric ceramics. By taking all, the applied electric field is all applied to the ceramic and is sufficiently polarized. Further, according to this polarization method, the electrode for polarization is not necessary, and the step for forming the electrode can be omitted. Further, the cost of the electrode can be reduced, and thus the manufacturing cost can be reduced.

In the second aspect of the present invention, thin plate-shaped piezoelectric ceramics finished to a certain size by machining are aligned and stacked in the thickness direction, and dummy blocks made of the same material are placed at both ends and pressed. Then, as in the first invention, by pressing a conductive material having plasticity and applying a high voltage for polarization, the dummy blocks at both ends are made of the same material as the thin plate piezoelectric ceramics, so that the dummy blocks are aligned. The electric field is not disturbed even at both ends of the thin plate-shaped piezoelectric ceramics, and the electric field is evenly applied to all the thin plate-shaped piezoelectric ceramics, so that the variation in the piezoelectric characteristics is reduced.

Further, if a sheet forming method by a doctor blade method is adopted as a method for manufacturing a thin plate piezoelectric ceramic, the manufacturing cost of the thickness-sliding vibrator is significantly reduced because slice processing is not required even after polarization.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of manufacturing a thickness sliding oscillator according to an embodiment of the present invention will be described below with reference to the drawings, focusing on a polarization process.

(Embodiment 1) FIG. 1 shows a polarization process of piezoelectric ceramics in a first embodiment of the present invention. In FIG. 1, 1 is a plurality of thin plate-shaped piezoelectric ceramics without electrodes, 2 is a conductive rubber installed so as to be in close contact with the piezoelectric ceramics, 3 is a conductive rubber 2 is in close contact with the piezoelectric ceramics 1. A copper plate is provided for the purpose of achieving conductivity, and a reference numeral 4 is a spring for pressing the copper plate 3 in order to bring the conductive rubber 2 into close contact with the piezoelectric ceramics 1. It should be noted that members other than the above-mentioned lead wires used for polarization are shown in FIG.
The same thing as the thing of the code | symbol 14-18 shown in was used.

First, Pb (Zn _1/3 Nb _2/3 ) _x Ti _y Zr
The _Z O ₃ -MnO ₂ based piezoelectric ceramic powder of the slurry together with a binder and molding the green sheet having a thickness of 0.37mm in the sheet forming machine of the doctor blade method.
This was trimmed to a size of 32 × 38 mm, 15 sheets of zirconia spread powder were piled up between the trimmed green sheets, and the top and bottom were sandwiched by a setter made of zirconia and put in an alumina sheath and baked. .

Using a dicing machine to measure this into a size of 25 × 5 mm
By cutting, a thin plate-shaped piezoelectric ceramic 1 was produced. this
80 sheets in the thickness direction (after firing about 0.31 mm)
Hey, conductive parts on both sides corresponding to one of the facing end faces.
Apply the conductive rubber 2 made of silicon as the material
Install a pair of copper plates 3 with a thickness of 4 mm, and push with the spring 4.
I got it. Copper plate 3 is attached to conductive rubber 2 by spring 4.
In addition, the conductive rubber 2 adheres to the piezoelectric ceramics
It serves as an electrode for the pole. Here
The conductive rubber 2 made of silicon used in Step 2 has a heat resistant temperature of 150.
℃, specific resistance 1 × 10 ^-2Ω · cm. Siri this
Put it in a mixture oil and apply a voltage of 15kV at 100 ° C for 30 minutes.
It was applied and polarized.

After polarization, cleaning, and polishing in the thickness direction with a precision grinder to adjust the frequency, an excitation electrode is formed on a surface parallel to the polarization direction by a vacuum deposition method, and the performance as a thickness-sliding oscillator is obtained. Was measured. As a conventional example, a thickness sliding oscillator described below was manufactured and its performance was also measured.

First, 25 × 30 having the same composition as that of this embodiment.
Silver paste was applied as a polarization electrode to both main surfaces of a 25 × 30 mm square of a 5 × 5 mm piezoelectric ceramic block by a screen printing method, and baked at 700 ° C. for 5 minutes. Then, after polarization was performed by the conventional polarization method shown in FIG. 3, the electrode for polarization was removed, and this was 0.27 mm with a slicing machine.
Slicing was performed to the thickness of, and frequency adjustment and excitation electrode formation were performed in the same manner as in this example, and then the performance as a thickness slip oscillator was measured. As a result, there was no difference in electrical performance or frequency variation between the conventional example and this example. However, in both cases, the electromechanical coupling coefficient was 3 to 7% lower only in the thin plates (corresponding to two sheets) positioned 0.6 mm from both ends during polarization.

As described above, when the polarization method of this embodiment is used, the conventional steps of forming and removing the electrode for polarization can be omitted, and the electrode material silver is not required. Further, in the present embodiment, since the green sheet is used for the piezoelectric ceramic 1 having a thin plate shape, the conventional step of slicing the piezoelectric ceramic block becomes unnecessary, and material loss due to the slicing of the piezoelectric ceramic material does not occur.

(Embodiment 2) Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a diagram for explaining the polarization process in the present embodiment. The difference from the first embodiment is that the piezoelectric ceramics 1 produced in the same manner as in the first embodiment are aligned, but both sides are made of piezoelectric ceramics of the same material. This is a point that is pinched and polarized in the dummy block 5 having a thickness of 5 mm.

The performance of this embodiment as a thickness sliding oscillator was measured and compared with the conventional example described in the first embodiment. As a result, in this case as well, there was no difference in electrical performance or frequency variation compared to the conventional example. Further, the decrease in the electromechanical coupling coefficient at both ends observed in Example 1 was not seen, and the material yield was improved as compared with Example 1.

[0023]

As is clear from the above description, according to the present invention, a plurality of thin plate-shaped piezoelectric ceramics are stacked and aligned, and a conductive member is closely adhered to polarize the piezoelectric ceramics. And the step of removing the same are not required, the manufacturing process can be shortened, the expensive precious metal electrode material can be saved, and the thickness sliding oscillator can be manufactured at low cost, which is of great economic value. .

[Brief description of drawings]

FIG. 1 is a diagram illustrating a polarization process in a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a polarization step in the second embodiment.

FIG. 3 is a diagram illustrating a conventional polarization process.

FIG. 4 is a diagram for explaining a conventional piezoelectric ceramic cutting process.

[Explanation of symbols]

 1 Piezoelectric ceramics 2 Conductive rubber (conductive member) 3 Copper plate 4 Spring 5 Dummy block

Claims (2)

[Claims] 1. A plurality of thin plate-shaped piezoelectric ceramics are stacked in the thickness direction to form an assembly, and conductive members are pressed against opposite surfaces of the assembly parallel to the thickness direction. A piezoelectric ceramics polarization method for applying a high voltage to a conductive member. 2. A plurality of thin plate-shaped piezoelectric ceramics are stacked in the thickness direction thereof, and then both sides in the thickness direction are sandwiched by dummy blocks made of the same material as the piezoelectric ceramics to form an assembly. A method for polarizing a piezoelectric ceramics, wherein a conductive member is pressed against opposite surfaces parallel to the thickness direction and a high voltage is applied to the conductive member.