JPS63108610A - Manufacture of piezo-electric ceramic - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing piezoelectric ceramics, and in particular, an object of the present invention is to easily form a thin plate and to form a molded body of any shape.

(Prior Art) Ferroelectric materials such as lead zirconate titanate (hereinafter referred to as PZT) and barium titanate (hereinafter referred to as BaTi0a) can convert electrical signals into mechanical signals and vice versa. Are known. By molding the ferroelectric material into a plate shape, forming electrodes on both sides of the fired material, and maintaining the electric field strength determined by the material for a certain period of time.

A piezoelectric ceramic is formed by performing a polarization process.

This piezoelectric ceramic is widely used in ultrasonic diagnostic devices, fish finders, ultrasonic detectors, ultrasonic microscopes, and the like. Since each of these devices has a different purpose of use, the frequency applied to the piezoelectric ceramic is 10 kHz to 200 kHz,
It covers a fairly wide band from several MHz to 100 MHz.For example, in ultrasonic diagnostic equipment (human body examination), PZT
The thickness is 0.3 to 0.4-11+, and driving at a high frequency (several MHz) is required for high resolution.
Thinner plates are required.

Now, typical piezoelectric materials such as PZT and BaTiO3
In order to manufacture piezoelectric ceramics using this method, the same method as conventional ceramic manufacturing was used. That is, piezoelectric ceramic material powder is placed in a mold and pressurized.

Generally, the molded product is molded and then fired after being taken out.

(Problems to be Solved by the Invention) The mold pressing method as described above essentially has two defects. First, since it is used as a mold, its size is practically limited. 2nd & There is a drawback.

It was difficult to obtain a molded body having a large area, for example, a thickness of p 60 yam or less.

For this reason, VC, which manufactures thin plates of ferroelectric materials in large areas, usually uses a large mold, makes a molded body with a thickness that can be molded with this mold, and after firing, processes such as polishing or etching are used to make the thin plate. However, these methods have disadvantages in terms of both poor material yield and man-hours, and manufacturing costs.

Also, these piezoelectric ceramics are not flexible.

There are restrictions on the shapes that can be molded, which limits the applications. Another method is to make a thin plate using a piezoelectric material by vapor deposition or sputtering, but this method allows for a wider area than the above-mentioned mold pressing method, but the film thickness is only a few micrometers at most, making ultrasonic diagnostics possible. It is not suitable for use in equipment as it is too small. Also, instead of using piezoelectric ceramics, an example of an organic piezoelectric material + hVDF
Although there are examples of using polyvinylidene fluoride (polyvinylidene fluoride), in general, organic piezoelectric materials are compared to piezoelectric base materials.

There was a problem with sensitivity.

(Means for Solving the Problems) The present invention solves the above-mentioned drawbacks by uniformly dispersing a sintered fine powder of two ferroelectric plates in a dispersion liquid called a polymer latex and vulcanizing the same.

A thin and large-area flexible composite is obtained, which is then sandwiched between molds of arbitrary shape, all of the polymer latex is incinerated at a low temperature, and then fired at a higher temperature to produce piezoelectric properties of a predetermined thickness. The present invention provides a piezoelectric ceramic that is flattened and has an arbitrary shape. This will be explained in detail below.

In the present invention, ferroelectric plate powder such as PZT, BaTiO3, etc. is dispersed and stirred in ion-exchanged water.

Acrylonitrile butiethane latex (hereinafter referred to as NB)
A polymer latex such as styrene-butiethane latex (hereinafter referred to as SBR) is mixed in an amount of 3 to 10 percent by weight per 100 percent by weight of the strong electric conductor plate-fired powder.

After sufficiently dispersing the powder, the polymer latex is vulcanized to form a composite of the ferroelectric sintered powder and the polymer latex. Next, the composite is washed with water, kneaded, and rolled into a predetermined thin plate using rollers. This composite has flexibility due to the action of the polymer latex.

The thin plate-like composite obtained above is sandwiched and molded into a ceramic mold having an arbitrary shape such as a flat or spherical shape depending on the purpose. After that, put the -44 between the molds into an electric furnace and burn off all the polymer latex.
'C) A sintered body is obtained by firing at a higher temperature. After firing, electrodes are attached using methods such as vapor deposition, spraying, and screen printing, followed by nine polarization treatments to obtain piezoelectric ceramics.

(Example) PZT calcined fine powder having an average powder diameter of 1.3 am was mixed in 200 mJ of 100 ker on-exchanged water and stirred.

After thorough dispersion, 4.2 gr of NBR was mixed and stirred, and after thorough dispersion, 10 gr of n-butyl acrylate was added as a vulcanizing agent.

5 oyr of 0.1 mol/l sulfite water and 2 CNIr of 1 mol/e hydrochloric acid water are mixed into the dispersion and mixed in a ball mill for 1 hour to obtain a composite.

゛The composite obtained by the above method is swimming and kneaded.

After sufficiently drying, it is rolled and formed using roller 1 as shown in Figure 1.
A composite body 2 having a flexible thin plate shape and a large area is manufactured.

The arrow indicates the direction of rotation of the roller. The composite 2 was cut into an appropriate size and molded between molds 3 and 4 having spherical surfaces made of zirconia as shown in FIG. At this time, it was desirable to apply fine powder of magnesia or zirconia to improve release from the mold after firing. Then, it was placed in an electric furnace at 500°C for 210 hours, and the NB
R was completely incinerated and removed from the thin plate-like composite. NBR
After being completely incinerated and removed, the thin plate molded body was fired at 1250°C to obtain a thin plate-shaped PZT having a thickness of 300 mm, 9 areas, 50 mm, and 100 mm.

Electrodes were formed on both sides of the thin plate-shaped molded body by vapor deposition.
After applying a DC electric field of 0 Kv/crlL, it was short-circuited in a constant temperature bath at 100°C, aged for 10 hours, and then heated again at 20 KV/c in silicone oil at 120°C for 20 minutes.
A DC electric field of rIL was applied to complete one polarization process.

When we measured the piezoelectric properties of this piezoelectric ceramic with a spherical surface, we found that the piezoelectric constant of thickness vibration was d33 = 181 x 10
-12C/N, kt = 0.52, it was confirmed that it had almost the same piezoelectric properties as a piezoelectric ceramic made with the same composition by a normal firing method.

In this example, the area is 50 m x 100 am, but by appropriately selecting the amount of the composite before rolling and the size of the firing furnace, a sheet piezoelectric ceramic having an even larger area can be obtained. Also.

In this example, the composite is formed from 1 ferroelectric plate baking powder, but the composite may be formed from 9 ferroelectric raw materials.

Further, in the two embodiments, a ferroelectric material having one spherical surface is fired, but shapes other than one spherical surface do not impair the above-mentioned content.

(Effects of the Invention) As explained above, one aspect of the present invention is to form a fine powder of a ferroelectric plate into a dispersion containing a polymer latex.

By uniformly dispersing and vulcanizing, a thin and flexible composite with a large area can be obtained.

Furthermore, by sandwiching it in a mold of an arbitrary shape, incinerating and removing all the polymer latex at a low temperature, and then firing it at a higher temperature, a piezoelectric ceramic that is thin, has a large area, and has an arbitrary shape is obtained by crushing the piezoelectric properties. be able to.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are a form diagram of rolling forming and a sectional view of a baking mold, respectively, according to an uninvented embodiment. 1 is a roller, 2 is a composite, 3 is a 6-plate, and 4 is a concave plate.

Claims (1)

[Claims] A ferroelectric sheet-fired powder is suspended in a dispersion containing an appropriate amount of polymer latex, mixed and stirred, and the polymer latex is vulcanized in a state uniformly dispersed in the ferroelectric sheet-fired powder, thereby making it flexible. After forming the composite into a desired thickness and shape, the polymer latex contained in the composite is removed by incineration at a low temperature, and then fired at a high temperature to obtain a sintered body. A method for manufacturing piezoelectric ceramics, characterized in that a polarization treatment is performed after attaching an electrode to a compact.