JPS6350323A - Monocrystalline tio2 substance doped with ta and its production - Google Patents

Abstract

PURPOSE:To easily obtain pure monocrystalline substance in a simple process by mixing TiO2 and Ta2O5 in the specified proportion, pressure molding the mixture and calcining it in air. CONSTITUTION:95.0-98.5mol% TiO2 and 1.5-5.0mol% Ta2O5 are mixed and the mixture is pressure molded and thereafter calcined in air. By such a way, monocrystalline TiO2 substance consisting of 90.0-97.0mol% TiO2 and 3.0-10.0mol% Ta and being doped with Ta is obtained. The above-mentioned molded body doped with Ta consists of polycrystalline substance well-regulated in crystal size and this polycrystalline substance is made easily separable into every crystalline particles by easily causing intercrystalline cracking and is separated into monocrystalline particles by crushing it. In case the proportion of Ta doped in monocrystalline substance is less than 3.0mol%, the granular growth of crystal is not caused but it is made dense and the intercrystalline cracking is not caused. On the other hand, in case the proportion of Ta is more than 10.0mol%, the granular growth of crystal is irregularly caused and the intercrystalline cracking is not caused. Also crushed particles are polycrystalline particles and monocrystalline particles are not obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to Ta-doped T, which is used for elucidating the particle growth state in the firing process of metal oxides and investigating physical properties.
This invention relates to an iO2 single crystal and its manufacturing method.

[Conventional technology]

Conventionally, TiO2 single crystal particles having a diameter of about several tens of micrometers have been used as TiO2 single crystals used for the above-mentioned purpose, and these have been produced by the following method.

First, titanium oxide powder as a solute and potassium fluoride powder as a medium are mixed. This mixture is heated to a temperature higher than the melting point of the medium to melt the solute and medium.

Thereafter, the medium is cooled at a cooling rate of about 10° C./hr to a temperature at which it solidifies, and then naturally cooled to room temperature in the furnace. In this way, a lump-like substance composed of a single crystal of +Ti○2 and a medium is obtained.

Further, in order to make this into single crystal grains, the following processing is performed. First, a lumpy melt is placed in a beaker, poured with 80°C warm water, and left to stand for more than ten minutes, then the hot water is discarded and the beaker is washed with hot water. When such hot water washing is repeated, the medium components in the mass gradually break down and dissolve, leaving behind insoluble particles.

By repeating this several times, each particle size becomes 30 to 50 μm.
Single crystal particles of about m are obtained.

[Problem that the invention seeks to solve]

However, the above-mentioned TiO2 single crystal.

As impurities, about 500 ppm of potassium and 1100 ppm of fluorine are included. Since this impurity is contained within the single crystal, it cannot be removed no matter how many times hot water washing is repeated.

Furthermore, in order to finally obtain a single crystal powder from a lumpy melt, it is necessary to undergo several hot water washings as already mentioned. Therefore, there are problems in that the process is complicated and large-scale cleaning equipment is required.

The present inventors took into consideration the above-mentioned conventional problems in the conventional TiO2 single crystal and its manufacturing method.

As a result of investigation, we found that TiO2 doped with Ta at an appropriate ratio
The authors focused on the fact that the polycrystalline material forms a polycrystalline body with a uniform crystal size, and that this polycrystalline body easily causes grain boundary fracture. The present invention is based on this point.

The purpose is to solve the above conventional problems.

[Means for Solving the Problem] The Ta-doped TiO2 single crystal according to the first invention has a TiO2 content of 90.0 to 97.0 mol%.

It consists of 3.0 to 10.0 mol% of Ta.

Further, in the method for producing the above-mentioned single crystal according to the second invention, TiO2 is contained in an amount of 95.0 to 9885 mol%.

This is a method in which a Kono>H compound containing 1,5 to 5,0 mol/l/% of Ta2O5 is pressure molded and then fired in air.

[For production]

In the method for producing single crystal particles according to the second invention, a mixture of TiO2 and l'a2 os as raw materials is pressure-molded and then fired in air.

A Ta-doped TiO2 molded body according to the first invention as shown in FIG. 1 is obtained. This molded body consists of a polycrystalline body with a uniform crystal size, and furthermore, this polycrystalline body easily causes intergranular fracture and is easy to separate into individual crystal grains. It is separated into single crystal particles such as: These single crystal grains are based on the shape of the individual crystal grains that make up the polycrystal as shown in Figure 1.
Even after crushing, it remains as it is.

In addition, in the first invention, the reason why the proportion of Ta is limited to the above range is as follows. When the proportion of doped Ta in the single crystal is less than 3.0 mol %, grain growth of the crystal does not occur, the crystal becomes dense, and two-grain boundary fracture does not occur. Moreover, the pulverized particles are polycrystalline, and single-crystal particles cannot be obtained. On the other hand, when the proportion of Ta is more than 10.0 mol %, grain growth of the crystal occurs irregularly, and grain boundary fracture does not occur either. Moreover, the pulverized particles are polycrystalline particles, and single-crystalline particles cannot be obtained.

Further, the proportion of Ta2O5 in the raw material according to the second invention is necessarily determined from the proportion of Ta.

〔Example〕

Next, the present invention will be explained in detail.

(Example 1) TiO2 powder with a purity of 99.99% 85. OOg, 15.00 g of Ta2O5 powder with a purity of 99.99%, and 400 mβ of ethanol were mixed in a ball mill for 15 hours.

This mixture was dried at a temperature of 100°C, and TiO2 and Ta
A mixed powder of 2O5 was obtained. 15g of an organic binder containing 4% polyvinyl alcohol was added to the mixed powder, stirred with a crusher, passed through a 5Q mesh sieve, and
Powders with a size of μm or less were selected.

This powder was heated to a diameter of 15 mm at a pressure of 1 ton/am2.
11φ.

A plurality of molded products were made by pressure molding into a disc shape with a thickness of 2 ml.

The molded product was fired in air with a first-order temperature profile. First, the temperature was raised to 1450°C at a heating rate of 150°C/hr.
After increasing the temperature to 300℃/
The mixture was heated at a rate of 1 hr and taken out from the furnace at room temperature. As a result, a sintered body consisting of a crystalline body as shown in FIG. 1 was obtained.

The obtained sintered body was placed in a crusher and coarsely crushed for 30 minutes, then ethanol was added and crushed in a ball mill for 15 hours.
Particles having a particle size of 18 to 29 μm as shown in FIG. 2 were obtained.

As a result of analyzing this particle by X-ray diffraction, it was confirmed that it was a single crystal particle of TiO2 containing 6.0 mol% of Ta.

Its purity was 99.99%. The above results are summarized in Table 1.

(Example 2) In Example 1, the amount of TiO2 powder in the raw material was changed to 85.
00g to 80.62g, and the amount of Ta2O5 powder was changed to 15.0g. Single crystal particles were produced using the same method and conditions as in Example 1, except that OOg was changed to 19.38g.

These particles are single crystal particles of TiO2 containing 8.0 mol% of Ta, have a particle size of 17 to 33 μm, and have a purity of 99.9.
It was 9%. The results are shown in Table 1.

(Example 3) In Example 1, the amount of TiO2 powder in the raw material was changed to 85.
Single crystal particles were produced using the same method and conditions as in Example 1, except that OOg was changed to 89.67g and the amount of Ta2O5 powder was changed from 15.00g to 10.33g.

This particle is a single crystal particle of TiO2 containing 4.0 mol% of Ta, the particle size is 13 to 25 μm, and the purity is 99.99%.
Met. The results are shown in Table 1.

(Example 4) In Example 1, the amount of TiO2 powder in the raw material was changed to 85.
00g to 92.12g, and the amount of Ta2O5 powder was changed to 15.0g. Single crystal particles were produced using the same method and conditions as in Example 1, except that the weight was changed from OOg to 7.88 g.

These particles are single-crystal particles of TiO2 containing 3.0 mol% of Ta, have a 2-particle diameter of 17 to 24 μm, and a purity of 99.9.
It was 9%. The results are shown in Table 1.

(Example 5) In Example 1, the amount of TiO2 powder in the raw material was changed to 85.
Single crystal particles were manufactured using the same method and conditions as in Example 1, except that the amount of 'l'a2OS powder was changed from 15.00 g to 23.50 g.

These particles are single crystal particles of TlO2 containing 10.0 mol% of Ta, have a particle size of 25 to 36 μm, and have a purity of 99.9499.
．． It was 99%. The results are shown in Table 1.

(Comparative Example) Table 1 shows the particle size and purity of TiO2 single crystal powder produced by the conventional production method described above.

〔Effect of the invention〕

As explained above, T doped with Ta at the above ratio
iO2 is obtained as a polycrystalline substance with a uniform crystal size, which easily undergoes grain boundary fracture. Therefore, the single crystal particles according to the first invention can be obtained by simply pulverizing this polycrystal, and there is no need to perform the troublesome hot water washing as in the conventional method. Therefore, the process is simplified and.

No cleaning equipment is required.

In addition, since single crystal particles can be produced without using a medium,
It has the effect of easily obtaining a pure single crystal.

[Brief explanation of drawings]

FIG. 1 is an electron micrograph showing the crystal structure of the sintered body before pulverization in the second invention, and FIG. This is a micrograph of the sintered body after it has been crushed. Inventor Arai Subbed Sasazawa - Male

Claims (1)

[Claims] 1. Ta-doped T consisting of 90.0 to 97.0 mol% of TiO_2 and 3.0 to 10.0 mol% of Ta
iO_2 single crystal. 2. 95.0 to 98.5 mol% of TiO_2 and Ta_
A method for producing a Ta-doped TiO_2 single crystal, in which 1.5 to 5.0 mol% of 2O_5 is mixed, pressure molded, and fired in air.