JPS5957951A - Method for manufacturing ZnS polycrystal - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing ZnS polycrystals.

(Background of the technique) ZnS polycrystals have good infrared light transmittance, so they are often used as windows and lenses in infrared equipment.

Conventionally, ZnS polycrystals have been mainly produced by chemical vapor deposition (Chcmi).
It is manufactured by a CVD method (hereinafter referred to as CVD method) and is commercially available. This method involves the reaction of Zn vapor and 1(2S gas) (Z
n -1-H2S → ZnS +) I2) ↓ This method involves depositing polycrystalline ZnS compounds on a substrate, and large-scale window materials with dimensions of several hundred am are also produced using large-scale reactors. .

Typical light transmission characteristics of ZnS produced by CVD method are shown in Figure 1.
Shown below. It shows good transmittance of 70% or more in the wavelength range of 2 to 10 μm, but 6 μm? There is a clear impurity absorption peak near n, and on the short wavelength side including the visible light region of 2μ or 2-0.4μ7, there is a tendency for the transmittance to gradually decrease, which is thought to be caused by some scattering particles. It is a characteristic.

Non-uniformity in transmittance due to absorption and scattering is harmful when used as a window material or lens of an optical system for infrared equipment, depending on the wavelength band used. In particular, as an optical element for a system that uses both infrared light and visible light (for example, a system that combines an infrared detector and a telephoto camera), it has been desired to improve the transmittance in the visible light range.

In view of the points mentioned above, the present inventors have developed ZnS by CVD method.
As a result of investigating various ways to improve the light transmission properties of polycrystalline materials, we found that
We have found a treatment method that significantly reduces absorption and scattering.

(C) Disclosure of the Invention (CVI) A ZnS polycrystalline body obtained by the CVI method is heated at a temperature of '750 to 1050' (:,
By raising the temperature and pressurizing the pressure to 100 atmospheric pressure or more, 6
It was revealed that the impurity absorption peak near μm and the scattering in the range of 2 to 04 μm were significantly reduced.

As a result, a hot isostat press (Hot Isostat)
icPressing, hereinafter referred to as HIP. ) after Z
It was also found that nS became colorless and transparent in appearance, and the yellow to orange appearance color before IIP completely changed.

5.III I) will be briefly explained. As shown in Figure 2, HIP is a process in which a target sample 4 is placed in a sealed container 5, or if there is no risk of gas entering the sample and there is no risk of deterioration or contamination, the sample 4 is placed in a heater. While heating at step 6, the enclosure container or the entire sample is heated under high pressure at step 7.
By isotropically pressurizing (mainly inert gas such as argon, nitrogen, helium, etc.), the vacancies 1111:
This is a method to obtain high-density samples.

Since high pressure gas is used, the heater 6, heat insulating layer 8, etc. are housed in a high pressure container 9.

■The IIP method can apply high temperature and isotropic pressurizing force from gas to the workpiece at the same time, so it has an excellent effect of removing internal defects such as pores and voids. Compared to the press method, this method has the advantage of being easier to manufacture complex shapes (for example, lens shapes, spherical shapes, etc.). Taking advantage of this advantage, it has been conventionally used for pressure sintering of powder in metal-based materials, removing cavities from casting, and removing internal defects in powder sintered bodies (cemented carbide, etc.) to improve mechanical properties. ” contributes to the second.

The present inventors applied this FIIP method for the first time to a ZnS polycrystalline material obtained by the CVI) method and found that the optical properties were significantly improved.

FIG. 1 shows typical light transmission characteristics of the ZnS polycrystalline material after HIP processing according to the method of the present invention. The impurity absorption peak (Zn
1I, .) has disappeared, and the transmittance on the short wavelength side of 0.4 to 2 μm has been significantly improved, reaching a transmittance of nearly 70%, which is almost the same as in the 2 to 10 ILm range. It is clear that this has been achieved. Moreover, 2-1
The transmittance in the 0 μη range is generally improved by several percent or more. Another phenomenon that should be noted is that the absorption edge is 11 I P
What was 0.4μッz before processing changed to 0.65μ772 after 1-1 IP processing, which contributed to a significant improvement in visible light transmittance (visually colorless and transparent). It is thought that there are.

Although the cause of this improvement effect has not yet been elucidated, it is presumed that the removal of ZnH2 as an impurity and the removal of micropores as a scattering factor are effective. It is thought that the reason why these impurities and micropores are removed is that the impurities and micropores are diffused and disappeared through grain boundaries due to the synergistic effect of temperature and pressure during IIIP processing.

In order to produce the effect described in -1-, both temperature and pressure are necessary. That is, the ZnS polycrystal obtained by the CVD method was heated in the same inert atmosphere as HIP with 2(ex゛Ar)
The temperature was raised only in medium temperature and 750 to 1050℃ in single temperature (
Typical light transmission characteristics in the case of annealing are shown in FIG. 16. Although a decrease in the impurity absorption peak near the wavelength of 6 μη2 is observed, the transmittance on the short wavelength side of 04 to 2 lb 772 has worsened, and the appearance has become pale yellow, cloudy, and translucent. I end up.

As a result of a detailed study of the HIP processing conditions for ZnS polycrystals, it was found that temperature conditions of 750 to 1050'C, pressure conditions of 500 atm or more''2 are appropriate for improving optical properties and other aspects. understood.

That is, at temperatures below 750'C, the diffusion effect is inactive.Since the softening of ZnS is insufficient, the micropores are crushed by pressure and the improvement effect is not sufficient. on the other hand,
Temperatures exceeding 1050'C are unsuitable for practical use because grain growth is significant and mechanical strength is extremely reduced. Furthermore, if the pressure is less than 500 atm, a sufficient improvement effect cannot be confirmed, and it is considered that the pressure is insufficient to collapse the micropores.

Example: ZnS polycrystal obtained by CVD method at 20×20X
Cut out 2+u+t and polish both sides to 0.2~20
Transmission spectra in the μm wavelength range were measured.

A graph similar to FIG. 1 was obtained. This sample was processed at 85°C without a capsule using a 11P apparatus using Ar gas as a pressure medium.
Processing was carried out under conditions of 0'C, 11,500 atmospheres, and 60 minutes.

After processing, the surface was polished again and the same transmission spectrum as before processing was measured. As a result, a graph similar to that shown in FIG. 1 and 2 was obtained, and a ZnS polycrystal that was colorless and transparent in appearance was obtained.

[Brief explanation of the drawing]

FIG. 1 shows a light transmission spectrum chart showing a typical example of the effect of improving optical properties 4 by the conventional method and the method of the present invention, and FIG. 2 shows an example of the I-11P method. 1: Transmission spectrum of ZnS by cvl) method 2: Transmission spectrum of ZnS by the method of the present invention 3: Transmission spectrum of ZnS after annealing in Ar gas 4: Sample 5: Piercing container 6: Heater procedure amendment document 1. Display of the case 1982 Patent Application No. 169046 2 Name of the invention Process for producing ZnS polycrystalline material 3 Person making the amendment Relationship to the case Patent applicant address 5-15 Kitahama, Higashi-ku, Osaka Name (213
) President of Sumitomo Electric Industries, Ltd. Tetsu Kawakami Department Director Address 1-1-3 Shimaya, Konohana-ku, Osaka City Sumitomo Electric Industries, Ltd. Drawings subject to 6 amendments Contents of 7 amendments Drawings, Figures 1 and 2 Correct the diagram as shown in the attached sheet.

Claims (2)

[Claims] (1) Zn characterized in that a ZnS polycrystal obtained by a chemical vapor deposition method is heated and pressurized by hot isostatic pressing.
Method for producing S polycrystal. (2) The method for producing a ZnS polycrystalline body according to claim 1, wherein the hot isostatic pressing conditions for the ZnS polycrystalline body are a temperature of 750 to 1050°C and a pressure of 500 atm or more.