JPH05254838A - Production of titanium-modified zirconia - Google Patents

Abstract

PURPOSE:To provide the method for producing titanium-modified zirconia having good dispersibility and capable of exhibiting excellent sinterability. CONSTITUTION:A method for producing the titanium-modified zirconia from an aqueous solution is characterized by adding a titanium salt aqueous solution to a suspension of a monoclinic zirconia hydrate obtained by the hydrolysis of a zirconia salt, hydrolyzing the titanium salt to change the suspension into a suspension of a mixture comprising the monoclinic zirconia hydrate and the tetragonal titania hydrate, and subsequently calcining the precipitated products.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing titanium-modified zirconia.

[0002]

2. Description of the Related Art Titanium-modified zirconia is used as a raw material when a lead zirconate titanate (PZT) -based or lead lanthanum zirconate titanate (PLZT) -based piezoelectric material is synthesized by a dry method. ing. Such titanium-modified zirconia is usually synthesized by a coprecipitation method or a hydrolysis method from an aqueous solution or suspension containing a zirconium salt, a titanium salt or the like.

In the above coprecipitation method, a zirconium salt and a small amount of a titanium salt are brought into contact with an aqueous solution to coprecipitate a hydroxide of zirconium and titanium, and the precipitate is filtered and dried. And calcination to obtain titanium-modified zirconia. In the hydrolysis method, a liquid obtained by mixing a small amount of titanium salt with a zirconium salt is maintained at a temperature of about 100 ° C. to obtain a cloudy sol-like substance, which is then filtered, dried and calcined to obtain titanium-modified zirconia. Is the method.

And, these manufacturing methods add a small amount of titania to zirconia to introduce heterogeneity into the system.
That is, it is intended to achieve a uniform mixture of zirconia and titania by giving a certain distribution (non-uniformity) in particle size, composition and the like.

However, with these methods, it is extremely difficult to introduce sufficient inhomogeneity at the particle level, even if the mixing can be done uniformly at the ion level.
Therefore, the titanium-modified zirconia powder obtained by these manufacturing methods has low dispersibility and easily agglomerates. In other words, the powder having such agglomeration cannot exhibit excellent sinterability even when fired, so it cannot be said to be the most suitable raw material for the piezoelectric material or the like.

Therefore, at present, development of a method for producing titanium-modified zirconia, which is optimal as a raw material for piezoelectric materials and the like, has been earnestly desired.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing titanium-modified zirconia having good dispersibility and exhibiting excellent sinterability.

The inventors of the present invention have conducted extensive studies in view of the above-mentioned problems of the prior art, and as a result, mixed suspension obtained by adding a titanium salt to a suspension of monoclinic hydrated zirconia and hydrolyzing it. By preparing zirconia particles and titania particles having a certain range of particle size from a suspension obtained by hydrolyzing a suspension or a suspension of tetragonal hydrated titania containing a zirconium salt. , Succeeded in introducing heterogeneity at the particle level. Then, they found that the titanium-modified zirconia obtained thereby exhibited excellent dispersibility, and completed the present invention.

That is, the present invention relates to the following first invention and second invention.
(First invention) In a method for producing titanium-modified zirconia from an aqueous solution, a suspension of monoclinic hydrated zirconia obtained by hydrolyzing a zirconium salt is added with an aqueous titanium salt solution. In addition, by hydrolyzing the titanium salt, the suspension is made into a mixed suspension of monoclinic hydrated zirconia and tetragonal hydrated titania, and the resulting precipitate is calcined. Method for producing titanium-modified zirconia. (Second invention) In a method for producing titanium-modified zirconia from an aqueous solution, a zirconium salt aqueous solution is added to a suspension of tetragonal hydrated titania obtained by hydrolyzing a titanium salt to hydrolyze the zirconium salt. Thus, the suspension is formed into a mixed suspension of tetragonal hydrated titania and monoclinic hydrated zirconia, and the resulting precipitate is calcined, which is a method for producing titanium-modified zirconia.

The first aspect of the present invention will be described in detail below.

First, a suspension of monoclinic hydrated zirconia is prepared by hydrolyzing a zirconium salt.
The zirconium salt used here is not limited as long as it is water-soluble, but zirconyl oxychloride, zirconyl oxynitrate and the like are particularly preferable. Of these, inexpensive zirconyl oxychloride is particularly preferable.

The zirconium salt is dissolved in water to obtain a zirconium salt aqueous solution having a concentration of usually 2 mol or less, preferably about 0.1 to 1 mol. If the concentration is more than 2 mol, the hydrolysis reaction is remarkably slowed, and if it is less than 0.1 mol, it is uneconomical.

Next, a zirconium salt aqueous solution is usually added to 80-2.
By hydrolyzing by heating at about 00 ° C. for about 10 to 100 hours, monoclinic hydrated zirconia having an average particle diameter of 0.01 to 0.2 μm is produced, and the aqueous solution is a suspension of hydrated zirconia. It becomes liquid. In this case, the temperature is 200 ℃
Although the reaction is possible even if it exceeds, it is not practical due to operational problems such as the need for a high pressure resistant container. On the other hand, if the reaction temperature is lower than 80 ° C., the hydrolysis reaction becomes slow, which is not preferable. If the reaction temperature is 100 ° C. or higher, an autoclave can be used. If the above reaction time exceeds 100 hours, the production efficiency may be reduced. Further, if it is less than 10 hours, the hydrolysis reaction is not sufficient, and moreover, the number of hydrated zirconia particles produced may be less than 0.01 μm, which is not preferable. In this hydrolysis reaction, it is possible to use a catalyst such as caustic soda, caustic potash, ammonia, hydrogen peroxide, etc., if necessary.

Next, an aqueous solution of titanium salt is added to the above suspension to hydrolyze the titanium salt, and the suspension is mixed with a mixed suspension of monoclinic hydrated zirconia and tetragonal hydrated titania. To do. The titanium salt used here is not limited as long as it is water-soluble, but titanium tetrachloride, titanium nitrate, titanium oxynitrate, titanium oxysulfate, titanium alkoxide and the like are particularly preferable. Among these, titanium tetrachloride is more preferable because it is inexpensive and easily available. In this case, the concentration of the titanium salt in the mixed suspension is usually 2 mol or less, preferably about 0.1 to 1 mol. If the above-mentioned concentration exceeds 2 mol, the hydrolysis reaction becomes slow, and if it is less than 0.1 mol, it becomes uneconomical, which is not preferable. The amount of the titanium salt with respect to the zirconia is such that the titania is 10 to 90% with respect to the total number of moles of zirconia and titania.
If the above amount is less than 10%, the dispersibility of the powder obtained will be poor and the powder will easily aggregate. Further, if it exceeds 90%, the dispersibility of the powder is deteriorated, which is not preferable.

Next, the suspension containing the aqueous titanium salt solution is heated at room temperature (about 20 ° C.) to about 100 ° C. for about 10 to 100 hours to carry out hydrolysis to give an average particle size of 0.01 to 0. Tetragonal hydrated titania of 0.02 μm is produced, and the aqueous solution becomes a mixed suspension of monoclinic hydrated zirconia and tetragonal hydrated titania. In this case, the crystallinity of the hydrated titania produced tends to be higher as the reaction temperature is lower, and if the temperature of the produced hydrated titania crystals is adjusted to the extent that the zirconia aggregation is suppressed. good. Further, if the reaction time exceeds 100 hours, the production efficiency may decrease. On the other hand, if the reaction time is less than 10 hours, the hydrolysis reaction is not sufficient, and moreover, the hydrated titania particles produced often have particle sizes of less than 0.01 μm, which is not preferable. In this hydrolysis reaction, if necessary, for example, caustic soda, caustic potash, ammonia,
It is also possible to use a catalyst such as hydrogen peroxide.

The mixed suspension of monoclinic hydrated zirconia having a constant particle size and tetragonal hydrated titania obtained as described above is sufficiently stirred. Since the particles in this suspension have excellent dispersibility, both particles easily disperse with each other,
A homogeneous mixed suspension results.

After sufficient stirring, filtration and washing are carried out by a conventional method, and then drying is usually carried out at about 80 to 100 ° C. for about 10 to 24 hours. Then, the obtained mixture of monoclinic hydrated zirconia and tetragonal hydrated titania (titanium modified zirconia precursor) is usually added at about 600 to 800 ° C.
By calcination for about 10 hours, titanium-modified zirconia in which monoclinic zirconia and tetragonal titania are uniformly mixed can be obtained. Further, after calcination, if necessary, it may be pulverized by a wet ball mill or the like so that the average particle diameter is 0.1 μm or less, and in this case, the dispersibility is not lost.

In the case of the second invention of the present invention, a zirconium salt aqueous solution is added to a suspension of tetragonal hydrated titania obtained by hydrolyzing a titanium salt under the same conditions as in the first invention, and the zirconium salt is added. If the hydrolysis is carried out under the same conditions as in the first invention, the same mixed suspension as in the first invention can be obtained. Then, by the same operation as the first invention, filtration, washing,
Titanium-modified zirconia is finally obtained by drying and calcination

..

According to the production method of the present invention, titanium-modified zirconia having excellent dispersibility can be produced relatively easily. The titanium-modified zirconia powder thus obtained can exhibit excellent sinterability due to its dispersibility, and is therefore extremely useful as a raw material for manufacturing piezoelectric materials.

[0020]

EXAMPLES Examples will be shown below to further clarify the characteristics of the present invention. Example 1 Zirconyl oxychloride aqueous solution 2 having a concentration of 2.72 mol / l 2
94.1 cm ³ was diluted to 4 liters with water and hydrolyzed in a closed container at 100 ° C. for 100 hours to obtain a suspension of hydrated zirconia. When the suspension was observed with a transmission electron microscope, the hydrated zirconia particles had a particle size of about 0.1 μm.

To the above suspension, 41.15 cm ³ of titanium tetrachloride aqueous solution having a concentration of 4.86 mol / l was added, and the mixture was kept at 50 ° C. in a closed container and hydrolyzed for 100 hours to form hydrated titania. A mixed suspension of monoclinic hydrated zirconia and tetragonal hydrated titania was obtained. When the suspension was observed with a transmission electron microscope, it was confirmed that the hydrated zirconia particles and the hydrated zirconia particles having a particle size of about 0.01 μm were formed.

Next, the mixed suspension was sufficiently stirred and then filtered, washed and dried by a conventional method to obtain a hydrated zirconia hydrated titania mixture (titanium modified zirconia precursor). X-ray diffraction analysis of this mixture confirmed that it consisted of monoclinic zirconia and tetragonal titania. The result of the X-ray diffraction analysis is shown in FIG. Further thermal analysis of the mixture revealed that the mixture was (Zr _0.8 T
i _0.2 ) O ₂ .0.5H ₂ O was found.
The results of thermal analysis (TG-DTA experiment) are shown in FIG.

Then, the above mixture was calcined at 800 ° C. for 2 hours to obtain a powder of titanium-modified zirconia in which monoclinic zirconia and tetragonal titania were uniformly mixed. When this powder was observed with a transmission electron microscope, the average particle size was 0.3 μm, and no agglomeration of powder particles was observed. The result is shown in FIG. The BET specific surface area of the powder was 30 m ² / g. Example 2 Zirconyl oxychloride aqueous solution 2 having a concentration of 2.72 mol / l
By diluting 39.0 cm ³ to 4 liters with water and performing hydrolysis at 100 ° C. for 100 hours in a closed container,
A hydrated zirconia suspension was obtained. When the suspension was observed with a transmission electron microscope, the particle size of the hydrated zirconia particles was about 0.1 μm.

To the above suspension, 72.0 cm ³ of a titanium tetrachloride aqueous solution having a concentration of 4.86 mol / l was added, and hydrolysis was carried out at 50 ° C. for 100 hours in a sealed state.
Hydrated titania was generated to obtain a mixed suspension of monoclinic hydrated zirconia and tetragonal hydrated zirconia.

When the suspension was observed with a transmission electron microscope, it was confirmed that the suspension consisted of hydrated zirconia particles having a particle size of about 0.1 μm and hydrated titania particles having a particle size of 0.01 μm.

Next, after thoroughly stirring the above-mentioned mixed suspension, filtration, washing and drying were carried out by a conventional method to obtain a hydrated zirconia hydrated titania mixture (titanium modified zirconia precursor). When this mixture was calcined at 800 ° C,
An agglomerate-free titanium-modified zirconia with a chemical composition of (Zr _0.65 Ti _0.35 ) O ₂ was obtained.

The obtained titanium-modified zirconia 35.20
9 g, 67.704 g of commercially available lead oxide and 4.887 g of lanthanum oxide were put in a ball mill and mixed for 2 hours.
By calcining at 800 ° C for 2 hours, (Pb
_0.91 La _0.09 ) (Zr _0.65 Ti _0.35 ).
_{A PLTZ} powder having a chemical composition of _0.9775 O ₃ was obtained. This powder was formed into a pellet at a pressure of 100 MPa, and hot pressed and sintered at 1200 ° C. for 1 hour in the coexistence of lead oxide vapor and oxygen gas. The density of the obtained sintered body is 7.
At 81 g / cm ³ , the light transmittance was 61% (600 nm) in the sample having a thickness of 1 mm.

[Brief description of drawings]

1 is a result of an X-ray diffraction analysis of a titanium-modified zirconia precursor obtained in Example 1. FIG.

FIG. 2 is a result of thermal analysis of the titanium-modified zirconia precursor obtained in Example 1.

FIG. 3 is an electron micrograph (30,000 times) showing a particle structure of titanium-modified zirconia obtained in Example 1.

Claims (2)

[Claims] 1. A method for producing titanium-modified zirconia from an aqueous solution, wherein an aqueous solution of titanium salt is added to a suspension of monoclinic hydrated zirconia obtained by hydrolyzing a zirconium salt to hydrolyze the titanium salt. By doing so, the suspension is made into a mixed suspension of monoclinic hydrated zirconia and tetragonal hydrated titania, and the resulting precipitate is calcined, which is a method for producing titanium-modified zirconia. 2. A method for producing titanium-modified zirconia from an aqueous solution, wherein an aqueous zirconium salt solution is added to a suspension of tetragonal hydrated titania obtained by hydrolyzing a titanium salt to hydrolyze the zirconium salt. Thus, the suspension is formed into a mixed suspension of tetragonal hydrated titania and monoclinic hydrated zirconia, and the resulting precipitate is calcined, which is a method for producing titanium-modified zirconia.