JP3210992B2 - Method for producing titanium-modified zirconia - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing modified titanium zirconia.

[0002]

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

In the above coprecipitation method, an aqueous solution obtained by adding a small amount of a titanium salt to a zirconium salt is brought into contact with an alkali to coprecipitate a hydroxide of zirconium and titanium, and the precipitate is filtered and dried. And calcining to obtain titanium-modified zirconia. Further, in the hydrolysis method, a liquid obtained by mixing a small amount of a titanium salt with a zirconium salt is kept 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. That is the method.

[0004] These production methods introduce a heterogeneity into the system by adding a small amount of titania to zirconia.
In other words, a uniform distribution (non-uniformity) is given to the particle size, composition, and the like, so as to achieve uniform mixing of zirconia and titania.

[0005] In these methods, however, it is extremely difficult to introduce sufficient non-uniformity at the particle level even if the mixing can be performed uniformly at the ion level.
Therefore, the dispersibility of the titanium-modified zirconia powder obtained by these production methods is low, and aggregation easily occurs. In other words, a powder having such agglomeration cannot exhibit excellent sinterability even when fired, and therefore cannot be said to be optimal as a raw material for a piezoelectric material or the like.

Therefore, development of a method for producing titanium-modified zirconia that is optimal as a raw material of a piezoelectric material or the like is currently desired.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing titanium-modified zirconia which has good dispersibility and can exhibit excellent sinterability.

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

That is, the present invention provides the following first invention and second invention.
(1st invention) In a method for producing titanium-modified zirconia from an aqueous solution, a titanium salt aqueous solution is added to a suspension of monoclinic hydrated zirconia obtained by hydrolyzing a zirconium salt. In addition, by hydrolyzing the titanium salt, the suspension is made into a mixed suspension composed of monoclinic hydrated zirconia and tetragonal hydrated titania, and the resulting precipitate is calcined. Of producing modified titanium 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. A method for producing titanium-modified zirconia, wherein the suspension is made into a mixed suspension composed of tetragonal hydrated titania and monoclinic hydrated zirconia, and the resulting precipitate is calcined.

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

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

The above zirconium salt is dissolved in water to obtain an aqueous solution of a zirconium salt having a concentration of usually 2 mol or less, preferably about 0.1 to 1 mol. If the above concentration is more than 2 mol, the hydrolysis reaction will be remarkably slow, and if it is less than 0.1 mol, it will be uneconomical, which is not preferable.

Next, the aqueous solution of zirconium salt is usually mixed with
By performing the hydrolysis by heating at about 00 ° C. for about 10 to 100 hours, monoclinic hydrated zirconia having an average particle size of 0.01 to 0.2 μm is formed, and the aqueous solution is a suspension of hydrated zirconia. It becomes a liquid. In this case, the temperature is 200 ° C.
Although the reaction is possible even if the pressure exceeds the above, it is not practical due to operational problems such as the need for a high pressure vessel. On the other hand, when the reaction temperature is lower than 80 ° C., the hydrolysis reaction is undesirably slow. When the reaction temperature is 100 ° C. or higher, an autoclave can be used. If the reaction time exceeds 100 hours, the production efficiency may be reduced. If the time is less than 10 hours, the hydrolysis reaction is not sufficient, and the hydrated zirconia to be formed often has a particle size of less than 0.01 μm, which is not preferable. In this hydrolysis reaction, if necessary, a catalyst such as caustic soda, caustic potash, ammonia, and hydrogen peroxide can be used.

Next, an aqueous solution of a titanium salt is added to the above suspension to hydrolyze the titanium salt, and the above suspension is mixed with a mixed suspension of monoclinic hydrated zirconia and tetragonal hydrated titania. I 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 them, titanium tetrachloride is more preferable because of its low cost and availability. 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 concentration is more than 2 mol, the hydrolysis reaction will be slow, and if it is less than 0.1 mol, it will be uneconomical. The amount of the titanium salt with respect to the zirconia is such that 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 obtained powder is deteriorated, and the powder is easily aggregated. On the other hand, if it exceeds 90%, the dispersibility of the powder deteriorates, which is not preferable.

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

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

After sufficiently stirring, the mixture is filtered and washed according to a conventional method, and then dried at about 80 to 100 ° C. for about 10 to 24 hours. Then, a mixture of the obtained monoclinic hydrated zirconia and tetragonal hydrated titania (titanium-modified zirconia precursor) is usually heated at about 600 to 800 ° C. for 2 hours.
By calcining for about 10 to 10 hours, titanium-modified zirconia in which monoclinic zirconia and tetragonal titania are uniformly mixed is obtained. Further, after the calcination, pulverization may be performed by a wet ball mill or the like, if necessary, to reduce the average particle size to 0.1 μm or less. In this case, the dispersibility is not lost.

In the case of the second invention of the present invention, an aqueous solution of a zirconium salt is added to a suspension of tetragonal hydrated titania obtained by hydrolyzing the titanium salt under the same conditions as in the first invention. Is carried out under the same conditions as in the first invention, the same mixed suspension as in the first invention is obtained. Then, filtration, washing,
By drying and calcining, titanium-modified zirconia is finally obtained

[0019]

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

[0020]

The following examples are provided to further clarify the features of the present invention. Example 1 Aqueous zirconyl oxychloride solution 2 having a concentration of 2.72 mol / l
94.1 cm ³ was diluted to 4 liters with water and hydrolyzed at 100 ° C. for 100 hours in a closed vessel to obtain a suspension of hydrated zirconia. When this 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 was added 41.15 cm ³ of a 4.86 mol / l aqueous solution of titanium tetrachloride, and the mixture was kept at 50 ° C. in a closed vessel and hydrolyzed for 100 hours to form hydrated titania. Thus, a mixed suspension composed of monoclinic hydrated zirconia and tetragonal hydrated titania was obtained. Observation of the suspension with a transmission electron microscope confirmed that the suspension was composed of the hydrated zirconia particles and the hydrated zirconia particles having a particle size of about 0.01 μm.

Next, after sufficiently stirring the above mixed suspension, filtration, washing and drying were performed 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. FIG. 1 shows the result of the X-ray diffraction analysis. Further thermal analysis of the mixture showed that the mixture was (Zr _0.8 T
i _0.2) was found to be _{O 2} · 0.5H 2 _O.
FIG. 2 shows the results of the thermal analysis (TG-DTA experiment).

Next, the above mixture was calcined at 800 ° C. for 2 hours to obtain a powder of titanium-modified zirconia obtained by uniformly mixing monoclinic zirconia and tetragonal titania. When this powder was observed with a transmission electron microscope, the average particle size was 0.3 μm, and no aggregation of the 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 Aqueous zirconyl oxychloride 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 vessel,
A suspension of hydrated zirconia was obtained. Observation of this suspension with a transmission electron microscope revealed that the particle size of the hydrated zirconia particles was about 0.1 μm.

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

Observation of this suspension with a transmission electron microscope confirmed that the suspension consisted of the above 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 sufficiently stirring the above mixed suspension, filtration, washing and drying were carried out according to a conventional method to obtain a hydrated zirconia hydrated titania mixture (titanium-modified zirconia precursor). When this mixture was calcined at 800 ° C,
An agglomeration-free titanium-modified zirconia having 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 placed 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-press sintered at 1200 ° C. for 1 hour in the presence of lead oxide vapor and oxygen gas. The density of the obtained sintered body is 7.
At 81 g / cm ³ , the light transmittance of the sample having a thickness of 1 mm was 61% (600 nm).

[Brief description of the drawings]

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

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

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

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C01G 25/02 C04B 35/626

Claims (4)

(57) [Claims] 1. A method for producing titanium-modified zirconia from an aqueous solution, wherein an aqueous solution of a titanium salt is added to a suspension of monoclinic hydrated zirconia obtained by hydrolyzing the zirconium salt to hydrolyze the titanium salt. A method for producing a titanium-modified zirconia, wherein the suspension is converted into a mixed suspension comprising monoclinic hydrated zirconia and tetragonal hydrated titania, and the resulting precipitate is calcined. 2. The method according to claim 1, wherein the zirconium salt is hydrolyzed.
The average particle size of the obtained monoclinic hydrated zirconia is 0.01 to
0.2 μm, which hydrolyzes titanium salts
The average particle size of the tetragonal hydrated titania obtained is 0.01
2. The modified titanium zirconate according to claim 1, wherein the thickness is from 0.02 μm.
Near manufacturing method. 3. A method for producing titanium-modified zirconia from an aqueous solution, wherein an aqueous solution of a zirconium salt is added to a suspension of tetragonal hydrated titania obtained by hydrolyzing a titanium salt to hydrolyze the zirconium salt. A method for producing titanium-modified zirconia, wherein the suspension is made into a mixed suspension composed of tetragonal hydrated titania and monoclinic hydrated zirconia, and the resulting precipitate is calcined. 4. A compound obtained by hydrolyzing a titanium salt.
The average particle size of the tetragonal hydrated titania obtained is 0.01 to 0.1.
02 μm, to hydrolyze zirconium salts
The average particle size of the obtained monoclinic hydrated zirconia is 0.0
4. The modified titanium zirconate according to claim 3, having a thickness of 1 to 0.2 [mu] m.
Near manufacturing method.