JPS5815460B2 - Manufacturing method of transparent sintered body of zinc oxide - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing a translucent sintered body of zinc oxide.

Conventionally, the inside of a sealed pressure-resistant reactor grown by hydrothermal synthesis, that is, containing water, is kept at high pressure, a temperature difference is created inside the reactor, and zinc oxide seed crystals are placed in the low-temperature part and zinc oxide is placed in the high-temperature part. It is known that a zinc oxide single crystal obtained by depositing and growing zinc oxide on the surface of a seed crystal has translucency.

However, this method has the drawback that not only is the manufacturing method cumbersome, but also large-sized products cannot be obtained.

Furthermore, a method of growing single crystal zinc oxide using the Brax method is also known, but this method also yields only small crystals and cannot obtain large crystals.

On the other hand, sintered bodies of zinc oxide have been known for some time.

The manufacturing method includes (1) a method of manufacturing a sintered body without pores by increasing the sintering temperature of zinc oxide to increase the diffusion rate or by sintering it under reduced pressure;

(2) A method of adding impurities and performing liquid phase sintering.

(3) Many methods are known in which sintering is performed by extrinsically dissolving impurities to improve sinterability.

However, with these methods, it has not been possible to obtain a translucent fired body.

The present invention aims to obtain a material with excellent light transmittance by sintering zinc oxide without using a single crystal of zinc oxide.

As a result of our research to obtain a zinc oxide sintered body with excellent translucency, the present inventors first thermally decomposed organic acid zinc, zinc carbonate, zinc hydroxide, or a mixture thereof to produce zinc oxide,
This zinc oxide powder was heated at a temperature of 650 to 1000℃ for 30 minutes.
When pressure sintering is performed under a pressure of 0 kg/cm2 or more,
It was found that a translucent sintered body could be obtained.

At this time, the raw materials were inorganic zinc acids such as zinc sulfate, zinc nitrate, and zinc chloride, which were thermally decomposed to form zinc oxide, which remained transparent even when pressure was applied at temperatures of 650 to 1000 degrees Celsius. A sintered body could not be obtained.

However, as a result of further research, the zinc oxide obtained by thermally decomposing the above-mentioned inorganic acid zinc as a raw material can also be heated to a pressure of 1000 kg/cm2 or more, preferably 11
It has been found that a translucent sintered body can be easily obtained when it is 0oky/am2 or more.

The present invention provides zinc sulfate, zinc sulfate, and zinc chloride.
The seed or two inorganic acid salts are decomposed into zinc oxide at a temperature of 100° C. or lower, preferably 500° C. or lower, in air, reduced pressure, or a nitrogen atmosphere.

When the obtained zinc oxide powder is pressed at a pressure of 1000 kg/cm2 or more at a temperature of 650 to 1000 DEG C., a translucent sintered body of zinc oxide is obtained.

If the temperature is lower than 650°C, a sintered body cannot be obtained;
C It becomes difficult to take it out.

If the pressure is lower than 1000 kg/cm2, translucency cannot be obtained.

The highest pressure can be used until the mold withstands it.

When 5% by weight or less of an alkali metal is mixed with the zinc oxide powder, the pressure can be lowered to about 800 kg/cm 2 and the temperature can be lowered to about 500°C.

When the amount of the alkali metal mixed exceeds 5% by weight, grain growth is promoted and also causes isolated bubbles to remain, resulting in deterioration of translucency.

The mixture of alkali metals includes water-soluble alkali metal salts such as LiNO3, NaNO3, KNO3, RbNO3, C
8NO3 etc. are dissolved in water, mixed with zinc oxide powder and dried, and the dried product is used as a hot press sample.

Furthermore, if the zinc oxide powder aggregates or if the aggregation state is non-uniform, the light transmittance will be affected.

In such a case, this can be prevented by adding water, an alcohol, an organic solvent such as acetone, etc., and thoroughly kneading the mixture.

An example of a pressure sintering device is shown in FIG.

Figure 1 is a cutaway side view of the device, in which 1 is a mold made of Al2O3 polycrystalline material, 2 is a suppression plate made of A1□03 polycrystalline material, 3 is Al2O3 or BN powder to improve mold removal, and 4 is platinum powder. 5 is a plate, 5 is a zinc oxide powder, and 6 is a pressing rod.

Note that the material of the mold is not limited to Al2O3, but may also be cermet or the like that can withstand high pressure.

Moreover, the Al2O3 press plate 2 is not necessarily required.

After applying a predetermined pressure at room temperature, place it in an electric furnace and heat it at 10℃/
The temperature is raised to a predetermined temperature at a heating rate of min or less.

It is obtained by holding at a predetermined temperature for a predetermined time, allowing it to cool, and then taking out the sintered sample.

If the temperature increase rate is too high, the temperature gradient will increase,
The mold breaks due to thermal strain.

Example 1 Zinc oxide was obtained by heating zinc chloride in air at a temperature of 700 to 750°C.

This was ground into a powder of 0.3 μm or less.

The zinc oxide powder was pressure sintered using the apparatus shown in FIG. 1 under the following two conditions.

(1) Sintering was performed at a pressure of 1300 kg/cm2 and a temperature of 800°C for 2 hours.

(2) 1200kg/cm2 pressure, 80O~850℃
It was sintered for 10 to 20 hours.

In all cases, sintered bodies with excellent translucency were obtained.

Example 2 Zinc sulfate was heated in air at a temperature of 750 to 800°C to obtain zinc oxide.

This was pulverized to a powder of 0.3 μm or less, and pressure-fired in the same manner as in Example 1 under the following conditions.

(1) Sintering was carried out at a pressure of 1300 kg/cm2 and a temperature of 800°C for 3 hours.

(2) Sintering was performed at a pressure of 1250 kg/cm2 and a temperature of 800°C for 5 to 10 hours.

In all cases, sintered bodies with excellent translucency were obtained.

Example 3 A lithium nitrate aqueous solution was added to the same zinc oxide powder as in Example 1, stirred and heated, and dried to obtain a mixture of zinc oxide and lithium nitrate containing 1% by weight of lithium. pressure of 1200kg/cm2, 806℃
Pressure firing was performed for 2 hours.

A translucent sintered body was obtained.

Almost similar results were obtained when other alkali metals were used in addition to lithium.

Example 4 The same zinc oxide powder as in Example 2 was treated in the same manner as in Example 3 to obtain a mixture of zinc oxide and lithium nitrate.

This was pressure-fired in the same manner as in Example 2 at a pressure of 1250 kg/cm2 and a temperature of 800°C for 3 hours.

A translucent sintered body was obtained.

[Brief explanation of the drawing]

The drawing is a cutaway side view of an embodiment of the pressure sintering apparatus according to the present invention. 1: Al2O3 polycrystalline mold, 2: Al2O3 polycrystalline press plate, 3: Al2O3 or BN powder, 4: platinum plate, 5 zinc dioxide powder, 6: press rod.

Claims (1)

[Claims] 1. One or more inorganic acid salts selected from zinc sulfate, zinc nitrate, and zinc chloride are thermally decomposed to produce zinc oxide, and the zinc oxide powder is heated at a temperature of 650 to 1000°C. A method for producing a translucent sintered body of zinc oxide, which comprises performing pressure sintering at a pressure of 1000 kg/cm2 or more under the following conditions. , 2 1 selected from zinc sulfate, zinc nitrate and zinc chloride
A seed or two or more inorganic acid salts are thermally decomposed to produce zinc oxide, and 800 kg of zinc monoxide powder mixed with 5% by weight or less of an alkali metal is heated at a temperature of 500 to 1000°C. 1. A method for producing a translucent sintered body of zinc oxide, comprising pressure sintering at a pressure of /cm2 or more.