JP2541810B2 - Method for manufacturing piezoelectric ceramics for transducers - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing piezoelectric ceramics used in piezoelectric transducers such as underwater microphones.

[Conventional technology]

Conventionally, dense lead zirconate titanate-based piezoelectric ceramics have been mainly used for this type of piezoelectric element, but dense lead zirconate titanate-based piezoelectric ceramics have excellent properties such as very high energy exchange efficiency. However, in consideration of application to underwater microphones, it is difficult to match acoustic impedance with water, that is, the mechanical Qm is large, and ε ₃₃ / ε ₀ is large, so the piezoelectric constant g ₃₃ had drawbacks such as not being so large. In order to improve these shortcomings, various forms of ceramic-polymer composites have been investigated, including coral-shaped PZT composites made at the University of Pennsylvania State in the United States. It has been confirmed that the above-mentioned drawbacks of can be improved.

[Problems to be solved by the invention]

However, each of these methods has a drawback that the manufacturing method is complicated and mass productivity is poor (reference: coral replica method (DPSkinner et al.)). , There is a problem in mass productivity).

In view of the above-mentioned drawbacks, the present invention has an object to provide a method for producing piezoelectric ceramics having homogeneous and continuous voids easily and with high productivity.

[Means for solving problems]

According to the present invention, 100 parts by weight of lead titanium zirconate-based piezoelectric ceramic powder having a particle size controlled to 100 to 600 mesh is mixed with 1 to 8 parts by weight of a fibrous resin, and a binder is added to the mixture. After that, molding and firing are performed to obtain a piezoelectric ceramic having a large porosity.

Here, in the present invention, the particle size of the powder is limited to 100 to 600 mesh because the sintering reaction does not proceed so much with the powder larger than 100 mesh, and the strength of the finished sintered body is weak and it is practically used. This is because, on the contrary, in the case of powder of 600 mesh or less, the reaction proceeds too much and the porosity becomes small, which is out of the object of the present invention. The reason for limiting the amount of fibrous resin to 1 to 8 parts is that sufficient porosity cannot be obtained with 1 part or less, and conversely with 8 parts anomaly, the porosity will increase even if more than this is added. However, it is not practical because it is deformed and cracked and its strength is weak. Moreover, the reason why the resin is limited to fibrous ones is that the voids have continuity.

〔Example〕

 Hereinafter, examples of the present invention will be described in detail.

FIG. 1 shows a manufacturing process according to the present invention, the contents of which will be described.

First, similar to the conventional method for manufacturing titanium zirconate piezoelectric ceramics such as BaTiO ₃ and PbTiO ₃ , PbO, ZrO ₂ and Ti
O ₂ and other raw materials are weighed and mixed with a mixer such as a ball mill for several to several tens of hours.
Dry to obtain mixed powder.

The mixed powder is subjected to primary firing at a relatively high temperature of 1000 to 1300 ° C.

The lead zirconate titanate-based ceramics produced in this way is pulverized by a pulverizer so as to have an appropriate particle size distribution, and then classified by a classifier into a required particle size range to obtain a lead titanium zirconate-based raw material. Get a powder.

Next, to this raw material powder, add fiber-based resin such as cellulose, polyamide, polyester, etc., and mix them so that the raw material powder and the resin are sufficiently uniform, and then add a binder solution such as PVA and further mix. To do.

After adjusting the water content to an appropriate value, press molding is performed at a pressure of 0.5 to 1.0 Ton / cm ² .

Porosity with homogeneous and continuous voids by firing this compact in an appropriate atmosphere at 1000-1300 ℃
Piezoelectric ceramics of about 30 to 55% can be obtained.

At this time, the fiber-based resin used has a fiber shape,
Other materials such as cellulose can be applied as long as they are completely burned out.

Examples of the density and characteristics of the piezoelectric ceramics obtained by the above manufacturing method are shown below. Samples for measuring piezoelectric characteristics were coated with silver paste on the top and bottom surfaces of a φ10 × 25t round bar and then baked to form electrodes, and a voltage of 12.5 kV was applied at 200 ° C for 20 hours.
The voltage was applied for a minute to perform polarization treatment.

(Example 1) 100-200 mesh, 200-400 mesh, 400 as raw material
~ 600 mesh-Used lead-titanium zirconate-based powder with a particle size adjusted to 600 mesh, add 4 parts of cellulose to 100 parts of this powder, mix with an agate crusher for 30 minutes, and then add PVA as a binder to 0.5 parts. Fig. 2-a shows the porosity of a sample obtained by molding a mixture of 15 parts and mixing for 15 minutes at a pressure of 0.5 Ton / cm ² and firing at 1200 ° C. The permittivity ε ₃₃ / ε ₀ is shown in FIG. 2-b, and the piezoelectric constant g ₃₃ is shown in FIG. 2-c.

(Example 2) As a raw material powder, lead titanium zirconate-based powder having a particle size adjusted to 200 to 400 mesh was used.
Fig. 3-a shows the porosity of the sample prepared under the same conditions as in Example 1 by adding 1 part, 1 part, 4 parts, 8 parts, and 12 parts of cellulose. The permittivity ε ₃₃ / ε ₀ is shown in Fig. 3-b, and the piezoelectric constant g ₃₃ is shown in Fig. 3-c. In both cases, the permittivity ε ₃₃ / ε ₀ is 1 in the past.
The piezoelectric constant g ₃₃ was as high as 800 to 2000, and the piezoelectric constant g ₃₃ was as low as 20 to 30 (Vm / n), but according to the present invention, as is clear from FIGS. 2-c and 3-c, g ₃₃ is 80 to 130 (Vm / n). / N). Since the larger the piezoelectric constant g ₃₃ is, the higher the sensitivity becomes, it is an indispensable condition for piezoelectric ceramics used for piezoelectric transducers and the like. Desirably, 60 (Vm / N) or more is very useful. is there.

〔The invention's effect〕

As can be seen from the above description, the method for producing a porous piezoelectric ceramic according to the present invention is not much different from the method for producing a normal lead zirconate titanate-based ceramics, and it is easy to form a homogeneous and continuous amorphous pore portion. Since it is possible to obtain piezoelectric ceramics with a large porosity, it is of great industrial value.

[Brief description of drawings]

FIG. 1 is a flow chart showing a manufacturing process according to an embodiment of the present invention, FIG. 2-a is a correlation diagram between raw material powder particle size and void ratio of sintered ceramics, and FIG. 2-b is raw material powder particle size and dielectric. Correlation diagram with the ratio ε ₃₃ / ε ₀ , Fig. 2-c is a correlation diagram between the particle size of the raw material powder and the piezoelectric constant g _33, and Fig. 3-a is the amount of resin added and the porosity of sintered ceramics. Correlation diagram, Fig. 3-
b is a correlation diagram between the resin addition amount and the dielectric constant ε ₃₃ / ε _0, and FIG. 3C is a correlation diagram between the resin addition amount and the piezoelectric constant g ₃₃ .

Claims (1)

(57) [Claims] 1. To 100 parts by weight of lead titanium zirconate-based piezoelectric ceramic powder having a particle size controlled to 100 to 600 mesh,
1 to 8 parts by weight of a fibrous resin is mixed, a binder is added to the resin, and the mixture is molded and fired to obtain a piezoelectric ceramic with a large porosity and having uniform and continuous irregular pores. A method for manufacturing a piezoelectric ceramic for a transducer, which is characterized by the above.