JPH0337173A - Improvement of ir ray transmittance of zinc sulfide - Google Patents

Abstract

PURPOSE:To simply prepare a ZnS having relatively excellent IR ray transmittance in good productivity without requiring any large installation by heating and holding the zinc sulfide in zinc vapor. CONSTITUTION:Zinc sulfide is heated and held in zinc vapor to improve the IR ray transmittance thereof. The load of the zinc vapor relaxes the remained stress of the ZnS polycrystalline substance, namely the strain of the crystal lattice thereof, prepared with a hot press while keeping the stoichiometry thereof, thereby improving the IR transmittance. One of the reasons for improving the IR ray transmittance of the ZnS by the load of the ZnS vapor is estimated to be the relaxation of the remained stress, namely the strain of the crystal lattice, caused by the load of a large pressing pressure when the sample of the ZnS is made by a hot press.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for improving the infrared transmittance of zinc sulfide used as a window material or lens material for infrared-based equipment.

[Conventional technology]

Zinc sulfide (ZnS) has good transmittance for infrared rays with wavelengths of about 1 to 10 μm, and is therefore put into practical use as window and lens materials for devices that use infrared rays.

However, the infrared transmittance of ZnS is often only extremely low, about 75% of the theoretical value, depending on its manufacturing method.

For example, in the hot press method, the press pressure is 2 Ton/al.
1", sintering temperature about 900'c, ZnS powder (
Even if the particles are manufactured under the conditions of particle size of about 5 pm (purity 5 N: 99.999%), the current situation is that the infrared transmittance is usually only about 70% of the theoretical value.

According to this 1, in order to improve the infrared transmittance of ZnS to near the theoretical value, it is said that it is effective to perform HIP (p! p! hydrostatic press) treatment after hot pressing.

On the other hand, recently, Zn is produced by reacting Zn vapor with H and S.
High-quality ZnS has also been obtained using a method of growing S (Cvr) method (chemical vapor deposition method), but even in this case, approximately 75% of the theoretical value was achieved by performing HIP treatment at the end. is the current situation.

[Problem to be solved by the invention]

The prior art known as a method for producing ZnS having excellent infrared transmittance as described above has the following drawbacks or problems.

In other words, as mentioned above, it is difficult to obtain the theoretical value of infrared transmittance using only the hot press method, and although it is possible to obtain a value close to the theoretical value by applying HIP treatment, it requires a large amount of equipment. There is a drawback that it becomes expensive.

In addition, although the CVD method can obtain a product relatively close to the theoretical value, the growth rate of znS is extremely low at several tens of μm/H, and there are problems in production as a method for manufacturing a product with a small thickness. Further, by performing HIP treatment after CVD, it is possible to obtain approximately the theoretical value, but in this case, there is a drawback that the equipment becomes large-scale, as in the above-mentioned example. Therefore, the present invention aims to provide a method for easily obtaining ZnS with relatively excellent infrared transmittance, which has good productivity and does not require too much equipment.

[Means to solve the problem]

The present invention is a method for improving the infrared transmittance of zinc sulfide, which is characterized by heating and holding zinc sulfide in zinc vapor.

[Effect]

By loading Zn vapor, the stress remaining in the Zn8 polycrystalline body produced by hot pressing while maintaining the stoichiometry, that is, the crystal lattice strain, is alleviated, and the infrared transmittance is improved.

〔Example〕

First, ZnS of 30 gourd φ x 2 nods was made by hot pressing.
A polycrystalline material was produced. The conditions are ZnS powder purity 5
N (99,999%), powder particle size 0.5 μm 1 plain pressure 0.8 Ton/tx 2, sintering temperature 800 °C
1 vacuum atmosphere (approximately 10 Torr).

After manufacturing, it was optically polished and its infrared transmittance was measured using a double monochromator spectrophotometer. As a result, for example 2
．． The transmittance for infrared rays of 5 μm was 60%.

Next, a zinc vapor load test was conducted using the ZnS sample produced by this hot pressing.

The test procedure is as follows.

As shown in FIG. 1, the quartz tube 2 for supporting ZnS of the quartz tube 1
ZnS sump IVs is placed inside the quartz tube 1, and Zn is placed at the bottom of the quartz tube 1.
Powder 4 was vacuum sealed. After encapsulation, Zn powder 4 was heated to a constant temperature (727°C) while ZnS sample lv3 was heated to a constant temperature (727°C).
was heated in the range of Z 4 Torr to 86 Torr (the heating temperature of the Habo ZnS sample), and Zn vapor was loaded for 8 hours. Thereafter, infrared transmittance was measured.

FIG. 2 shows the infrared transmittance at 2.5 μm for the ZnS sample after loading with Zn vapor, and it can be seen that the infrared transmittance is improved by loading with Zn vapor. In Figure 2, the dotted line is Z before zinc steam loading.
The infrared transmittance of the nS sample, the circle mark indicates the infrared transmittance after loading with zinc vapor. Inside, without loading Zn vapor,
That is, when the sample was heated and maintained at 727°C in a vacuum, the infrared transmittance was decreased by about 10% compared to the sample after hot pressing.

From the above, by loading Zn vapor, Zn
One of the reasons why the infrared transmittance of S is improved is that Zn
It is conceivable that the residual stress, that is, the distortion of the crystal lattice, which occurs due to the application of large press pressure when creating the S sample by hot pressing, is alleviated by this method. however,
Since the properties deteriorate when heated and maintained in a vacuum, it is essential to load Zn vapor, and from this point of view, it is clear that the removal of residual stress is not the only reason for this.
It is thought that a phenomenon related to the so-called stoichiometry of nS is also involved.

The heating temperature for the ZnS sample is 727
Although the degree of improvement is somewhat limited when the temperature is raised above °C (
The reason is thought to be an increase in the amount of vacancy sons produced at high temperatures), and a similar effect was observed. However, ZnS is 1
．． It is desirable to heat a ZnS sample as an optical material to 1000°C or higher because it has a crystal transformation point at 020°C, that is, above this temperature, it is hexagonal, and below this temperature, it is cubic. I say no! not.

Needless to say, this effect can also be expected for ZnS produced by the CVD method.

〔Effect of the invention〕

According to the present invention, the infrared transmittance of ZnS can be improved, and ZnS with excellent infrared transmittance and excellent productivity can be obtained without increasing the size of the equipment as shown in the prior art.

[Brief explanation of drawings]

FIG. 1 is a detailed explanatory diagram of the present invention, and FIG. 2 is a diagram proving the effects of the present invention.

Claims (1)

[Claims] A method for improving the infrared transmittance of zinc sulfide, which is characterized by heating and holding zinc sulfide in zinc vapor.