JPH0475850B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to calcined powder of PLZT, specifically, a perovskite-type structure compound (hereinafter referred to as PLZT) consisting of lead, lanthanum, zirconium, titanium, and oxygen, and a solid solution thereof. This invention relates to a method for producing calcined powder as a raw material.

PLZT is widely used as functional ceramics such as optoelectronic materials, electrostrictive materials, piezoelectric materials, and sensors.

Recently, progress has been made in the direction of improving the functionality of PLZT, and technology has been developed to efficiently produce large amounts of calcined PLZT raw material powder that is easy to sinter, uniform, and low cost to meet these demands. It is requested.

[Prior art and its problems]

Conventionally, dry methods, coprecipitation methods, alkoxide methods, oxalic acid methods, and the like are known as methods for producing PLZT raw material calcined powder.

The dry method is a method in which compounds of the constituent raw materials Pb, La, Zr, and Ti are mixed in a dry method and the mixture is calcined. However, with this method, it is difficult to obtain a raw material calcined powder with a uniform composition, so
It is difficult to obtain PLZT, and the sinterability is not sufficient.

The coprecipitation method is a method in which a mixed solution is prepared by combining all of the constituent components, a precipitate-forming liquid such as an alkali is added to the mixed solution to cause coprecipitation, and this coprecipitate is dried and calcined.

This coprecipitation method has the drawback that particles coagulate during precipitation and drying to form secondary particles, making the particles of the calcined powder large and non-uniform, making it difficult to sinter. . Furthermore, it is difficult to use inexpensive titanium tetrachloride and zirconium oxychloride as raw materials because they form insoluble lead chloride.

On the other hand, in the alkoxide method and oxalic acid method, the raw materials and precipitate forming solution are expensive, and
It is difficult to produce PLZT calcined powder. Furthermore, although uniform particles can be obtained by coprecipitating each component, there are drawbacks such as the formation of coarse particles.

[Purpose of the invention]

The present invention uses a method that can eliminate the drawbacks of the conventional coprecipitation method, and furthermore, uses a wet method to produce PLZT that satisfies the requirements of easy sinterability, uniformity, and low cost.
It is an object of the present invention to provide a method for efficiently producing a raw material calcined powder of a solid solution thereof.

[Structure of the invention]

As a result of intensive research to achieve the above object, the present inventors have found that during the production of raw material calcined powder of PLZT and its solid solution, precipitation of at least Pb, Zr, and Ti components is sequentially and stepwise formed. The raw material calcined powder obtained by calcining a precipitate containing four components has a narrow particle size distribution, is composed of fine particles with uniform particle sizes, and has a uniform composition, making it easy to sinter and is extremely industrially advantageous. The inventors have discovered that it is possible to produce a raw material calcined powder of polyprovskite, and have arrived at the present invention.

In the present invention, a solution of each component of Pb, La, Zr, and Ti is brought into contact with a precipitate forming liquid to form a precipitate, and the precipitate containing the four components thus produced is calcined to produce lead, lanthanum, zirconium, titanium, and In a method for producing a calcined powder of PLZT, which is a raw material for a perovskite structure compound (hereinafter referred to as PLZT) consisting of oxygen and its solid solution, at least Pb,
The present invention relates to a method for producing a calcined powder of PLZT, which comprises calcining a precipitate containing the four components in which precipitates of each component, Zr and Ti, are successively produced in a stepwise manner.

PLZT and its solid solution of the present invention have the general formula
Pb _1-x La _x (Zr _y Ti _1-y ) _1-x/4 O ₃ x and y
can take various numbers depending on the application, but when used in optoelectronic materials, piezoelectric materials, etc., it is usually preferable that x be 0.01 to 0.15 and y be 0.2 to 0.8.

Component compounds for preparing solutions containing Pb, La, Zr, and Ti compounds, which are the constituent components of PLZT and its solid solution of the present invention, are not particularly limited, but their hydroxides, carbonates, and oxy These include inorganic salts such as salts, sulfates, nitrates, and chlorides, organic acid salts such as acetates and oxalates, and oxides. These are generally used as aqueous solutions. If it is not soluble in water, an acid may be added to make it soluble.

Examples of the precipitation forming liquid include ammonia (water), ammonium carbonate, caustic alkali, etc.
Among these, ammonia (water) is preferred from the viewpoint of cost and ease of washing the obtained precipitate.

Each solution containing Pb, La, Zr, and Ti compounds is brought into contact with a precipitate forming solution in multiple stages to form a precipitate, but the order of precipitate formation is at least Pb, Zr, and Ti.
There is no need to specifically limit the method as long as the precipitates of each component can be formed in a stepwise manner. The La compound may be mixed with one of the other component compounds to form a precipitate. In the present invention, at least Pb, Zr,
It is necessary to sequentially generate precipitates of each component of Ti, but the specific order of sequentially forming precipitates is, for example, Pb→La→Zr→Ti, Pb→La→ Ti→Zr order, Zr→Ti→Pb→La order, Zr→Pb+La→Ti order, Ti→La→Pb→Zr order, Ti→Zr→La→Pb order, Zr→Ti→Pb+La order Preferred examples include the order of Pb+La→Zr→Ti, and the order of Pb+La→Ti→Zr.

In addition, in the present invention, Zr and Ti are inexpensive and easily available.
Even when using chloride or oxychloride as a raw material component, a suitable raw material calcined powder for PLZT can be obtained since precipitation of lead chloride, which has been a problem in the past, does not occur. In this case, it is preferable to sufficiently remove chlorine ions from the obtained precipitate.

Although the precipitate produced according to the present invention is non-uniform in extremely small portions, the secondary particles forming the precipitate maintain uniformity. Therefore, there are no large aggregates as seen in the coprecipitation method, and uniform particles having a diameter of 0.05 to 0.5 μm are produced during calcination.

In order to form a precipitate of the constituent components, a method is generally employed in which an aqueous solution of each constituent component is successively added to a precipitate forming solution, but the method is not limited to this method. It is preferable that the addition be carried out with sufficient stirring of the liquid.

In addition, when producing a precipitate, for example, after producing a precipitate of one component, it may be washed with water to remove anions that would interfere with subsequent steps, and then the precipitate may be dispersed in fresh water to proceed to the next step. can.

Furthermore, when forming a precipitate of the constituent components, the shape of the resulting particles can be controlled by appropriately selecting and adjusting the type of precipitate forming liquid.

The precipitate obtained by the above method is washed, filtered, dried, and then calcined by a conventional method. Drying may be carried out under atmospheric pressure or under reduced pressure.

If the calcination temperature is too low, the dehydration and thermal decomposition of the precipitate will be insufficient, and if it is too high, the powder will become coarse.
A range of 1200°C is preferred.

〔Example〕

EXAMPLES The present invention will be explained in more detail by showing Examples and Comparative Examples below.

Example 1 Zirconium oxychloride (ZrOCl ₂ 8H ₂ O)
Dissolve 40.92 g in 700 ml of water and drop it into 1 part of 6N ammonia water to make hydroxide. Then, as a second step, 300 ml of an aqueous solution in which 12.99 g of titanium tetrachloride (TiCl ₄ ) is dissolved is added dropwise. As a step, 60.28 g of lead nitrate [Pb(NO ₃ ) ₂ ] and lanthanum nitrate [La
Aqueous solution 1 containing 7.79 g of (NO ₃ ) ₂ ·6H ₂ O was added dropwise to obtain a homogeneous precipitate of hydroxides of lead, lanthanum, zirconium, and titanium. This precipitate was washed, filtered, dried, crushed, and calcined at 700°C for 2 hours to obtain a raw material calcined powder of PLZT with a composition of Pb _0.91 La _0.09 (Zr _0.65 Ti _0.35 ) _0.9775 O ₃ . When this powder was observed using an electron microscope, the average particle size was approximately 0.1μ.
It consists of uniform particles of m, and as a result of measuring compositional fluctuations by X-ray diffraction, almost no compositional fluctuations were observed.

The above powder is mixed with polyvinyl alcohol (hereinafter referred to as
Add 0.8wt% of PVA (abbreviated as PVA, degree of polymerization 500) to 1t/cm ²
It was molded to a diameter of 20 mmφ and a thickness of 2 mm under the pressure of The transmittance of the obtained sintered body was measured using a spectrophotometer and was found to be 72% at a wavelength of 630 nm (thickness of 1.0 nm).
mm).

Example 2 Example 1 except that the lead nitrate and lanthanum nitrate solutions were dropped in the first stage, the zirconium oxychloride solution was dropped in the second stage, and the titanium tetrachloride solution was dropped in the third stage.
I did the same thing. The transmittance of the obtained sintered body was 70% at a wavelength of 630 nm (thickness: 0.9 mm).

Example 3 The same procedure as in Example 2 was carried out except that a titanium tetrachloride solution was dropped in the second stage, and a zirconium oxynitrate solution was dropped in the third stage. The transmittance of the obtained sintered body was 71% (thickness: 1.1 mm) at a wavelength of 630 nm.

Comparative Example 1 The same procedure as in Example 1 was carried out, except that a solution containing lead nitrate and lanthanum nitrate was dropped in the first stage, and a solution containing zirconium oxychloride and titanium tetrachloride was dropped in the second stage. The transmittance of the obtained sintered body is
It was 35% (thickness 0.8 mm) at 630 nm.

Comparative Example 2 The same procedure as in Example 1 was carried out, except that in the first stage, a solution containing zirconium oxychloride and titanium tetrachloride was dropped, and in the second stage, a solution containing lead nitrate and lanthanum nitrate was dropped. The transmittance of the obtained sintered body was 45% at a wavelength of 630 nm (thickness: 1.0 mm).

〔Effect of the invention〕

When producing raw material calcined powder of PLZT perovskite and its solid solution, Pb, Pb,
According to the method of producing precipitates of each component of Zr and Ti in a stepwise manner, a precipitate is obtained in which fine and uniform particles are highly interdispersed, and as a result, the precipitate is fine and difficult to cause agglomeration during calcination. , easily sinterable powder can be produced with good reproducibility.

In addition, in this process, each phase is highly mutually dispersed, so that the calcined material achieves sufficient uniformity. Further, since the process is simple, it has excellent effects such as being able to obtain easily sinterable powder with good reproducibility and at low cost.

When the raw material powder of the present invention is sintered, it has high translucency.
Since PLZT perovskite can be obtained, it is particularly suitable for optoelectronic materials.

Claims (1)

[Claims] 1 A solution of each component of Pb, La, Zr, and Ti is brought into contact with a precipitate forming solution to form a precipitate, and the precipitate containing the four components thus formed is calcined to form a precipitate consisting of lead, lanthanum, zirconium, titanium, and oxygen. In a method for producing a calcined powder of PLZT, which is a raw material for a perovskite structure compound (hereinafter referred to as PLZT) and its solid solution, precipitation of at least each of Pb, Zr, and Ti is sequentially and stepwise formed. PLZT characterized by calcining the containing precipitate
A method for producing calcined powder.