JP2996776B2 - Method for producing lead zirconate titanate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing lead zirconate titanate, and more particularly, to a piezoelectric element,
The present invention relates to a method for producing lead zirconate titanate used for a ferroelectric material such as a pyroelectric element and an electro-optical element by firing at a low temperature.

[0002]

2. Description of the Related Art Perovskite ferroelectrics such as barium titanate, lead titanate and lead zirconate titanate have been widely applied to capacitors and piezoelectric elements. In recent years, thinning and miniaturization of the above ceramics have become important issues for the needs for higher performance, smaller size, and lower cost of electronic materials.

Heretofore, lead zirconate titanate has been produced by pulverizing oxides of the respective component metals by a ball mill or the like, mixing the powders in a predetermined ratio, and then subjecting them to a solid phase reaction at a high temperature of 800 to 1300 ° C. . However, it is necessary to obtain high quality lead zirconate titanate because impurities cannot be avoided during the pulverization and mixing of the raw material oxides, and fine particles of 1 μm or less cannot be obtained by mechanical pulverization. There is a problem that can not be. Further, 1200 ° C. required to obtain the above ceramics
At the high firing temperature described above, there is a problem that the lead oxide is vaporized and the composition is not uniform. Therefore, recently, there has been a demand for a method for producing lead zirconate titanate having a uniform composition and which can be fired at a low temperature.

Regarding the low-temperature synthesis of the above ceramics,
Metal alkoxide [For example, Journal of the Ceramic Society of Japan,
98, 754 (1990), JP-A-62-108729], lead acetate and metal alkoxide [J. Appl. Ph
ys. , 64, 2717 (1988)], low-temperature sintering of lead zirconate titanate by a sol-gel method using hydrolysis of lead acetate, zirconium nitrate, and titanium butoxide [Journal of the Ceramic Society of Japan, 99, 630 (1991)]. It describes a method for synthesizing a conductive powder or a method for preparing a lead zirconate titanate thin film.

[0005]

However, in the above-mentioned method for producing lead zirconate titanate by a sol-gel method using a metal alkoxide as a raw material, the metal alkoxide used is hydrolyzed even in the presence of essentially a small amount of water. Since it is easily decomposed, it is difficult to prepare a sample at a predetermined mixing ratio, and furthermore, there is a problem that the storage stability of the mixed sample solution is poor. In addition, since the hydrolysis rates of the metal alkoxides of lead, titanium, and zirconium are different, the sol-gel method of preparing a precursor sol and gel of lead zirconate titanate by hydrolysis has a uniform composition and form. There is also a problem that it is difficult to obtain a suitable lead zirconate titanate. In addition to these, preparation of a lead zirconate titanate precursor by a sol-gel method requires complicated processing including the use of various additives to solve the above problems, There are also problems in the process, such as a long time required for gelation.

Accordingly, it is an object of the present invention to provide a method by which uniform lead zirconate titanate can be produced by low-temperature sintering without complicated steps.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, lead, titanium,
It has been found that uniform lead zirconate titanate can be obtained by heating a mixed solution of each organic acid salt of zirconium at a low temperature and thermally decomposing it.

As described above, it has been reported that the sol-gel method using a metal alkoxide or the like is effective for the conventional low-temperature synthesis of lead zirconate titanate.
According to the production method of the present invention, without preparing a sol-like and gel-like lead zirconate titanate precursor product by a condensation reaction, only the thermal decomposition or oxidative decomposition reaction of the organic acid salt used is performed directly. Lead zirconate titanate can be produced.

The lead zirconate titanate which can be produced by the present invention has a general formula: PbZr _x Ti _1-x O ₃ (where 0 ≦ x
PbZrO ₃ and PbT having a composition represented by ≦ 1.0)
It is a solid solution of iO ₃ . When other component elements are added to this solid solution (for example, Nb, Ta, Fe, Mg,
Y, La, etc.) and an organic acid salt of an additional element are mixed with a lead organic acid salt solution of lead zirconate titanate to easily obtain a uniform composition.

In the present invention, the lead zirconate titanate is a solution obtained by mixing a solution obtained by dissolving a predetermined amount of each of an organic acid lead, an organic acid zirconium, and an organic acid titanium in an organic solvent; A solution obtained by mixing predetermined amounts of zirconium acid and organic acid titanium in an organic solvent is dried at a temperature of 20 to 150 ° C, and then heated and calcined at 500 to 1000 ° C.

The lead compound that can be used in the method of the present invention is represented by the general formula: Pb (OCOR) ₂ , specifically, for example, lead stearate, lead laurate, lead caprylate,
-Lead ethylhexanoate, lead neodecanoate, lead naphthenate, etc., can be used alone or in combination of two or more.

The titanium compound used in the method of the present invention has a general formula: TiO _x (OCOR) _4-2x (where 0 ≦ x ≦ 1.
0) , specifically, for example, titanium stearate,
Titanium laurate, titanium caprylate, titanium 2-ethylhexanoate, titanium neodecanoate, titanium naphthenate
And the like, and polymers thereof . These can be used alone or in combination of two or more.

Further, the zirconium compound used in the method of the present invention has a general formula: Zr (OCOR) ₄ or ZrO
(OCOR) ₂ and specific examples thereof include zirconium stearate, zirconium laurate, zirconium caprylate, zirconium 2-ethylhexanoate, zirconium neodecanoate, zirconium naphthenate or zirconyl stearate, zirconyl caprylate,
-Zirconyl ethylhexanoate, zirconyl neodecanoate, zirconyl naphthenate, etc., which can be used alone or in combination of two or more, preferably organic zirconyl which does not cause hydrolysis. .

The organic solvent used in the method of the present invention includes n
-An organic solvent that dissolves the above-mentioned organic acid metal salt such as alcohols such as propanol, i-propanol and n-butanol; hydrocarbons such as hexane, heptane and cyclohexane; and aromatics such as benzene, toluene and xylene. Any solvent can be used, and these can be used alone or in combination of two or more. The amount of the solvent to be mixed is not particularly limited, but usually 3 to 2 parts of the organic solvent per 1 part by weight of the organic acid salt.
It is preferable to use about 0 parts by weight.

The mixed solution is first dried and then calcined. Drying is performed at 20 to 150 ° C for 0.2 to 2 hours, and baking is performed at 500 to 1000 ° C, preferably 500 to 800 ° C for 0.5 to 2 hours.

[0016]

Next, the present invention will be described in detail with reference to examples. Example 1 Lead octylate 50.0 g Zirconyl octylate 20.6
g, 27.6 g of titanium octylate in n-butanol 90
It was diluted and dissolved in 0 g. At that time, the atomic ratio of each metal is P
b: Zr: Ti = 1: 0.53: 0.47. First, the water stability of this solution was examined. The stability test by leaving it in the air at room temperature
It was stable even if left for more than a month. As a comparison, when titanium tetraisopropoxide or n-butoxide was used instead of titanium octylate as a titanium compound, a precipitate of titanium oxide hydrate began to precipitate only after being left for 1 hour, and completely when left for 2 days. To form a white precipitate. Next, an n-butanol solution of the above lead octylate, zirconyl octylate, and titanium octylate was added at 100 ° C.
After drying for 1 hour at 400 ° C., 500 ° C., and 600 ° C. for 1 hour, the obtained product was examined by powder X-ray diffraction analysis. The results are shown in FIGS.
The crystallinity was poor at 400 ° C. (FIG. 1), and the product could not be identified from the X-ray diffraction pattern. the X-ray diffraction pattern of the titanate di Rukon lead _(Pb 2 Z
r _0.52 Ti _0.48 O ₃ : JCPDS, Powder
r Diffraction File, 33-78
It was in good agreement with the X-ray diffraction pattern of 3). From this result, when n-butanol solution of lead octylate, zirconyl octylate, and titanium octylate is heated in the air,
It was found that lead zirconate titanate was formed at 500 ° C. or higher. The residual carbon content was 4% at 400 ° C and 1% at 500 ° C, but was not detected at 600 ° C (<
0.1%).

Example 2 Lead neodecanoate, zirconyl neodecanoate, and titanium neodecanoate were prepared in the same manner as in Example 1 except that Pb: Zr: Ti =
They were mixed at an atomic ratio of 1: 0.53: 0.47 and dissolved in butanol. This solution also remained stable when left in air for more than one month as described above. After drying this solution at 100 ° C. for 1 hour,
The product obtained by heating and sintering at predetermined temperatures of 1 ° C. and 600 ° C. for 1 hour was analyzed by powder X-ray diffraction analysis. The result was the same as that of Example 1, and at 500 ° C. or higher, lead zirconate titanate Was found to be generated. The residual carbon content was the same as the result of Example 1.

[0018]

The mixed solution of each of the organic acid salts of lead, titanium and zirconium used in the present invention is much more water-stable than the metal alkoxide solution which is a raw material for low-temperature synthesis of lead zirconate titanate which has been reported so far. There is no need to perform complicated operations at the time of solution preparation such as addition of a chelate compound, an alkanolamine or the like.
By employing the method of the present invention, lead zirconate titanate can be produced at a much lower temperature than in the conventional method using an oxide of a component metal as a raw material, which leads to a significant energy saving and is economically advantageous. It is. Also, unlike solid phase reactions,
Since thermal decomposition of a homogeneous solution of an organic acid salt generates lead zirconate titanate, a uniform composition can be obtained at a fine level. Furthermore, in the sol-gel method using a metal alkoxide or the like, complicated operations and steps are required to control the hydrolysis. In contrast, is the raw material used in the method of the present invention not hydrolyzable at all? Since it is very small, handling becomes easy, operations such as mixing and drying are simplified, and storage stability is greatly improved.

The method of the present invention can be applied to a method for producing lead zirconate titanate by various processes described below. Since lead titanate having a uniform composition can be produced by firing at a low temperature of about 500 to 600 ° C., it can be applied to synthesis of fine powder of uniform particles by a spray drying method or the like. In addition, it can be applied to the synthesis of thin films of uniform composition by printing methods such as screen printing and offset printing, spraying methods, dipping methods, spin coating methods, etc., and can sufficiently respond to thinning and miniaturization of lead zirconate titanate. It is.

[Brief description of the drawings]

FIG. 1 is a powder X-ray diffraction pattern of a product obtained at a firing temperature of 400 ° C. in Example 1.

FIG. 2 is a powder X-ray diffraction pattern of a product obtained at a firing temperature of 500 ° C. in Example 1.

FIG. 3 is a powder X-ray diffraction pattern of a product obtained at a firing temperature of 600 ° C. in Example 1.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-308801 (JP, A) JP-A-2-83214 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C01G 25/00 CA (STN)

Claims (1)

(57) [Claims] An organic acid salt of lead represented by the general formula: Pb (OCOR) ₂ , an organic acid salt of Ti represented by the general formula: Ti (OCOR) ₄ and a general formula: Zr (OCOR) ₄ or A method for producing lead zirconate titanate, comprising drying and firing a mixed solution of an organic acid salt of zirconium represented by ZrO (OCOR) ₂ .