JP2001181045A - Zinc sulfide-based sintering material, method for producing the same and sputtering target using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a zinc sulfide-based sintered material, especially a sputtering target material used for forming a zinc sulfide-based thin film and further provide a sintered compact for a sputtering target for forming the thin film of a protective film on a recording layer of a phase-change type optical recording medium having an alloy recording layer containing Te or Sb. SOLUTION: This zinc sulfide-based sintering material consists essentially of zinc sulfide and contains niobium oxide. The sintering material is converted into a zinc sulfide-based sintered compact and is used for the sputtering target by regulating the content of niobium oxide to 10-50 wt.% expressed in terms of Nb2O5 and regulating the surface resistivity thereof to <=10 Ω/square surface. The target of the sintered compact can be utilized for DC sputtering having a high thin-film forming rate. The sintered compact is obtained by preparing a mixture of a zinc sulfide powder having 0.5-20 μm average particle diameter with a niobium oxide powder having <=5 μm average particle diameter, hot pressing the resultant mixture at 800-1,100 temperature and providing the sintered compact of a desired shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a zinc sulfide based sintered material and a method for producing the same, and more particularly to a sputtering target material used for forming a zinc sulfide based thin film.

[0002]

2. Description of the Related Art Zinc sulfide-based materials are well known as phosphors and also known as electroluminescence. However, in the field of optoelectronics, they are used as light-transmitting thin films having a high refractive index. For example, a zinc sulfide-based thin film is T
In a phase-change optical recording medium using an alloy of e or Sb for a recording layer, it is used as a protective layer for protecting the recording layer. This medium is a CD-RW, DVD-RAM,
Although known as rewritable optical disks such as DVD-RW and DVD + RW, as shown in FIG. 1, a first protective layer 2 (21) is provided on a disk-shaped substrate 10, and a recording layer 3 is provided thereon. Is formed on the recording layer 3, a second protective layer 2 (22) is further formed, and aluminum,
The reflective layer 4 is formed of gold, silver, or an alloy containing the same as a main component.

[0003] The above-mentioned optical disk has a disk-shaped substrate 1.
The laser beam is irradiated from the 0 side, passes through the protective layer 2, irradiates the recording layer 3, is reflected by the reflective layer 4, and returns to the irradiation side via the recording layer 3 and the protective layer 2. During recording, a phase-change type optical recording medium is irradiated with a laser beam modulated in accordance with the signal intensity, and changes the phase of the recording layer 3 by the thermal energy thereof (for example, by changing the alloy thin film of the recording layer to a crystalline phase). Signal information is recorded as this phase change, and at the time of reproduction, a laser beam is irradiated to reflect the change in the reflection intensity of the laser light accompanying the phase change in the recording layer 3 as a signal. It is to detect.

The protective layer 2 transmits a laser beam and contacts the recording layer 3 to protect both surfaces thereof. For example, a composite material of ZnS-SiO ₂ is known. For example, this ZnS—SiO ₂ material has a molar ratio of 8
A composition having a composition of 0 mol% ZnS-20 mol% SiO ₂ is known.

The two-layer protective film 2 is formed in a thin film by an RF sputtering method. In this process, a disk-shaped substrate 10 and a target are placed in opposition to the disk-shaped substrate 10 in an RF sputtering apparatus.
Inside, a high-frequency plasma is generated to form a film on the disk-shaped substrate 10. Further, even after the formation of the recording layer 3, a film was formed on the recording layer 3 in an RF sputtering apparatus.

Conventionally, a ZnS—SiO ₂ sintered body has been used as a target material for this sputtering. For example, Japanese Unexamined Patent Publication No.
No. 138071. Examples of the method of forming a sintered body include a method of hot pressing a mixed powder of zinc sulfide and silica at a specific high sintering temperature in an inert gas atmosphere, and a method of forming a molded body of the mixed powder at normal pressure. A firing method has been used. Also, a method of performing hot isostatic pressing (HIP) to further densify the sintered body has been known.

[0007]

Conventionally, in order to form the protective layer 2 on the optical medium using such a ZnS-SiO ₂ sintered body, only the RF sputtering method can be used. . That is, since the ZnS-SiO ₂ sintered body has a high electric resistance, a direct current sputtering method cannot be used. In the RF sputtering method, it is difficult to apply a high electric power to a target, a sputtering speed is low, and The thin film productivity of the recording medium could not be increased.

Since such RF sputtering generates electric heating (high-frequency heating) by high frequency on the disk-shaped substrate 10 formed of a polymer, for example, polycarbonate, there is a danger that the disk-shaped substrate 10 may be thermally damaged. Also, from this point, there has been a problem of damage to the substrate 10 and productivity of the optical recording medium.

Further, the formation of the protective layer 2 may be used a target having a size corresponding to the dimensions of the disk-shaped substrate 10 is, although desirable for the control of the film thickness uniform, large ZnS-SiO ₂ sintered Since the compact is hard to be densified, there is a problem that the sintering strength is low and the production efficiency is low.

[0010] The sintered body as a target needs to have a small internal pore and a high relative density. That is, when sputtering is performed using a target made of a sintered body having a high porosity, it is difficult to maintain the atmosphere during sputtering at a high vacuum due to the release of air contained in the sintered body. If the composite material is formed without being kept in a vacuum, there is a problem that the composition of the thin film is shifted from the composition of the sintered body of the target. In addition, if the vacuum cannot be maintained at a high vacuum, the sputtering rate is reduced, so that the productivity of the thin film is low.

An object of the present invention is to provide a ZnS-based material having a low electric resistance and excellent sintering formability. An object of the present invention is to provide a film forming means of a type in which a current flows through a target, in particular, a sintered body of a ZnS-based material that can be used for DC sputtering.

[0012]

The sintered material according to the present invention is a zinc sulfide based sintered material containing zinc sulfide as a main component and niobium oxide. Although zinc sulfide (ZnS) itself is an insulator, the addition of niobium oxide in the sintered body lowers the electrical resistance of the ZnS-based sintered material and further increases the sinterability of the ZnS-based sintered material.

In the present invention, the form of niobium oxide in the sintered body is not necessarily clear, but niobium oxide includes a large number of oxides having a lower niobium oxidation number. In the following description, niobium oxide will be represented by Nb ₂ O ₅ for convenience, but is not limited thereto.

The ZnS—Nb ₂ O ₅ based sintered material of the present invention comprises:
Since the sintered body has a small electric resistance, it is used as a conductive ZnS-based sintered body. As such an example, the sintered body can be used as a target for forming a thin film. This sintered material can be used for a film forming means of a type in which an electric current flows through a target, particularly for forming a thin film by a DC sputtering method.

The thin film formed of the ZnS—Nb ₂ O ₅ based sintered material of the present invention is preferably used as a ZnS based protective layer for protecting a recording layer disposed on an optical recording medium. Can be.

More specifically, the zinc sulfide-based sintered material of the present invention reduces the electric resistance to a surface resistance of 100 Ω / □ or less by adding niobium oxide. In particular, when the sintered body contains more than 5% (% by weight, the same applies hereinafter) of niobium oxide as Nb ₂ O ₅ , the electric resistance of the sintered body is sharply reduced and conductivity is generated. Further, Nb ₂ O ₅ is adjusted to 10 to 5
A sintered body containing 0% has an electric resistance of 10% as a surface resistance value.
Ω / □ or less.

The sintered material containing 10 to 50% of Nb ₂ O ₅ is as follows:
It is excellent as a target for DC sputtering in terms of low electric resistance, and can supply a large amount of power to the target during sputtering film formation, increase the sputter film formation speed, and improve thin film productivity.

[0018] In the present invention, the addition of Nb ₂ O ₅ of ZnS-Nb ₂ O ₅ based sintered material enhances the sinterability of the sintered body, forming a plate-shaped sintered body having a large diameter without defects It can be used as a target for DC sputtering, and can be effectively used for forming an optical recording medium having a large-diameter disk-shaped substrate.

The present invention relates to a zinc sulfide based sintered material comprising a zinc sulfide powder having a particle size of 0.5 to 20 μm and a niobium oxide powder having an average particle size of 5 μm or less as raw materials for forming the zinc sulfide based sintered material. Including raw material powder.

The present invention is further produced by sintering from a mixture of a zinc sulfide powder and a niobium oxide powder having the above-mentioned particle size distribution.
A normal-pressure sintering method, a hot sintering method from a mixture (hot pressing method), and a hot isostatic pressing method (HIP method) of a compact can be used to form a sintered body having a desired shape.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The zinc sulfide based sintered material of the present invention comprises:
It is a sintered body containing ZnS as a main component and containing niobium oxide. Preferably, the content of niobium oxide exceeds 5% (% by weight, hereinafter the same) in terms of Nb ₂ O ₅ , 50
% Or less. Nb ₂ O ₅ is a component that lowers the electrical resistance of the ZnS—Nb ₂ O ₅ sintered material, but when its content is 5% or less, the electrical resistance is high, and Nb ₂ O ₅ is 5%.
Is exceeded, the surface resistance can be reduced to 100Ω / □ or less. In particular, from the sintered body itself, Nb ₂ O ₅
% Or more, and in this case, the surface resistance can be reduced to about 10 Ω / □ or less. On the other hand, the content of Nb ₂ O ₅ is preferably 50% or less in a sintered body containing ZnS as a main component.

Preferably, the zinc sulfide-based sintered material of the present invention contains more than 5% and not more than 50% of Nb _{2 in the} main component ZnS.
Contains O ₅ and is used as a target for forming a sputtering thin film. As the target for sputtering, the content of Nb ₂ O ₅ is particularly preferably in the range of 10-50%. 10% Nb ₂ O _{5 in} ZnS, the main component
By adding the above specific amount, the sintered body can obtain a surface resistance of at most 10Ω / □.
The thin film layer can be formed by sputtering. DC
Sputtering can easily supply a large current, thereby increasing the thin film forming speed and being effective in shortening the film forming process.

The zinc sulfide based sintered material of the present invention is preferably dense, and preferably has a relative density of 70% or more.
If the relative density is less than 70%, the strength of the sintered body is low, and it is particularly preferable that the relative density be 80% or more. In particular, as a sputtering target, a relative density of 70% or more is secured. If the relative density is less than 70%, the strength of the sintered body is low, and the formation rate of the sputtered film is too low. In particular, to increase the sputter film formation speed, the relative density 80
% Or more, and more preferably 90% or more in terms of relative density, from the viewpoint of preventing a reduction in the degree of vacuum at the time of sputtering and preventing a composition deviation of a formed thin film.

The zinc sulfide based sintered material or sputtering target of the present invention is formed by sintering a mixture of zinc sulfide powder and niobium oxide powder as raw materials. A 20 μm zinc sulfide powder and a niobium oxide powder having an average particle size of 5 μm or less are used.

The average particle size of the zinc sulfide powder is related to the densification and crack generation of the sintered body. For the densification, the zinc sulfide particles are preferably finer than 20 μm,
If it is larger than m, the zinc sulfide-based sintered material cannot be densified under normal firing conditions. In addition, such coarse particles cannot uniformly disperse the niobium oxide powder, so that local resistance value variation occurs. On the other hand, when the zinc sulfide particles are fine powder having a particle size of less than 0.5 μm, internal stress occurs during firing, and cracks often occur due to release of the stress.

The niobium oxide powder to be blended preferably has an average particle diameter of 5.0 μm or less, and if it exceeds 5.0 μm, the dispersion state of the niobium oxide is not uniform, and the local resistance value of the niobium oxide in the sintered body is low. Simultaneously with the occurrence of the variation, in addition to the cause of the composition deviation when the film is formed by sputtering, the quality of the obtained thin film also varies with respect to the quality stability, particularly the optical characteristics. .

For the production of a zinc sulfide-based sintered material, a sintering method is used in which a raw material powder obtained by mixing zinc sulfide powder and niobium oxide powder having the above-mentioned particle size distribution is held in a predetermined shape and fired. You. The sintering temperature for sintering is lower than the sublimation temperature of zinc sulfide, and on the other hand, a region where the sintering reaction is large is selected. The upper limit of the sintering temperature is preferably 1200 ° C. for the purpose of preventing sublimation, and the lower limit will be about 700 ° C.

As one method of manufacturing a zinc sulfide based sintered material and a sputtering target, a raw material powder of zinc sulfide powder and niobium oxide powder having the above-mentioned particle size distribution is hot-pressed into a sintered body having a desired shape. The method can be adopted.

At the time of hot pressing, the mixed raw material powder is filled in a press die having a desired inner surface shape, and is kept as it is at 150 kg / cm ² (14.7 Pa).
Sintering is performed by applying the above-mentioned surface pressure, heating and holding at the above-mentioned sintering temperature for a required time. The sintering temperature is preferably 80
Temperatures from 0 to 1100 ° C are available. At a firing temperature of 800 ° C. or lower, the sintering reaction is slow, and the relative density may be 80% or lower. When such a low relative density is used as a sputtering target, the rate of forming a sputtered film becomes low, and the strength of the sintered body itself becomes extremely low. This may cause cracking or loss of the sintered body.

In another production method, a raw material powder obtained by mixing a zinc sulfide powder and a niobium oxide powder is formed into a desired shape in advance, and the formed body is heated to 700 to 1200 ° C. in an inert gas.
At this temperature, a method of firing under normal pressure to obtain a sintered body can also be adopted.

In this method, the mixed raw material powder is compression-molded in a mold in a cold state in advance, and the molded body is heated and held at normal pressure to be sintered. In this method, an organic binder is added to the raw material powder of zinc sulfide and niobium oxide, and the shape of the desired sintered body is taken into consideration. The body is fired at normal pressure in the range of 700 ° C to 1200 ° C in an inert gas atmosphere.

In order to further densify the sintered body, the hot-pressed or normal-pressure-sintered sintered body is further subjected to a hot isostatic pressing at a temperature in the range of 800 to 1200 ° C. HIP). In this method, the pressure applied to the sintered body is set to 500 to 3000 Pa, and the sintering temperature in the range of 800 to 1200 ° C. can be used. If the pressure is 500 Pa or less and the sintering temperature is 800 ° C. or less, a sufficient densification effect by HIP cannot be obtained. In addition, even if the upper limit of the pressure exceeds 3000 Pa, the densification is saturated and cannot be expected.

By these sintering methods, a dense sintered body is obtained, and the sintered body has a relative density of 70% or more, and
0% or more can be secured, and in particular, a relative density of 90% or more can be obtained by using a hot isostatic press.

Regarding impurities in the raw materials, particularly, when used for the protective layer for the optical recording medium, zinc sulfide powder as a main component and niobium oxide as an additive include:
High-purity ones are preferred, and those with a purity of 99.9% or more are particularly preferred.

The metallic impurities such as Fe, Ni, Cu, Mn, and Pd are often contained as impurities in the zinc sulfide powder and the niobium oxide powder, but when these are present in the protective layer, the optical characteristics are impaired. And at the same time, significantly reduces the reliability of the thin film. For this reason, the raw material powder used for obtaining a sintered body is preferably as high as possible.

There are hexagonal and cubic zinc sulfides, both of which are used. However, hexagonal zinc sulfide powder has a lower reactivity with water than cubic zinc sulfide. , Can be prepared into a slurry. In this method, water and zinc sulfide powder are pulverized and kneaded to form a slurry, an organic binder is added, mixed, stirred, and then spray-dried to obtain a dry powder. This powder is easily formed into a green compact by molding, cold isostatic pressing, or the like, and is particularly easy to produce into a deformed product or a large product. It is possible to avoid complicated sintering methods such as hot pressing and the like, which enable normal pressure firing under an inert gas atmosphere.

The surface of the sintered body obtained by the above method is flattened by grinding or polishing in order to effectively function as a sputtering target.

[0038]

EXAMPLES Example 1 As raw materials, a hexagonal zinc sulfide powder having an average particle diameter of 4 μm and a purity of 99.9% and a niobium oxide powder having an average particle diameter of 0.3 μm and a purity of 99.9% were used. A raw material powder was obtained in which the content of niobium oxide was changed in the range of 0.5 to 30% with respect to the zinc sulfide powder.

Each raw material powder was dry-mixed for 24 hours using zirconia balls in a resin pot. After granulation, the temperature was raised to 900 ° C. at 3 ° C./min by hot pressing, and Ar
In an atmosphere, pressurizing at a surface pressure of 250 kg / cm ²
Sintering was performed for a time to obtain a disk-shaped sample made of a zinc sulfide-based sintered material having a diameter of 50 mm and a thickness of 5 mm. And
The surface resistance value of the obtained zinc sulfide-based sintered material was measured by a four probe method. Table 1 shows the measurement results.

[0040]

[Table 1]

From Table 1, it can be seen that when the Nb ₂ O ₅ content is 5.0% or less, the surface resistance of the ZnS—Nb ₂ O ₅ based sintered material does not change particularly, but exceeds 5.0%. And at a content of up to 10%, the surface resistance drops to 10Ω / □,
It turns out that it falls to 1 Ω / □ or less at 20 to 30%.

Example 2 This example shows an example in which a target was sintered by hot pressing. The raw materials include a hexagonal zinc sulfide powder having an average particle diameter of 4 μm and a purity of 99.9%, and a powder having an average particle diameter of 0.3 μm and a purity of 9 μm.
9.9% niobium oxide powder was utilized. 80% of the zinc sulfide powder and 20% of the niobium oxide powder were mixed to obtain a raw material powder. The raw material powder was dry-mixed for 24 hours using zirconia balls in a resin pot. After granulation, the temperature is raised to 900 ° C. at 3 ° C./min by hot pressing, and sintering is performed for 3 hours in an Ar atmosphere while pressing at a surface pressure of 250 kg / cm ² to form a disc having a diameter of 50 mm and a thickness of 5 mm. The obtained zinc sulfide based sintered material was obtained. The relative density and surface resistance of the zinc sulfide based sintered material were measured. The relative density was measured by the Archimedes method. Table 2 shows the obtained results.

The obtained sintered body was ground to a predetermined size with a diamond tool, and the sintered body was attached to a copper backing plate using In as a bonding material to prepare a sputtering target. Then, the obtained sputtering target was used for RF sputtering and DC sputtering to form a film on a quartz substrate.

As the conditions of the RF sputtering, an input power of 800 W and an Ar gas of 1 Pa were selected, and a film was formed on a quartz substrate to a film thickness of 1000 °.

As conditions for DC sputtering, DC power was set to 2 kW, Ar gas pressure was set to 1 Pa, and 100
The film was similarly formed on a quartz substrate so as to have a thickness of nm. R
Table 3 shows the film formation rates of F sputtering and DC sputtering and the properties of the obtained films.

Example 3 This example shows an example in which a target was sintered by normal pressure firing using a slurry. As in Example 2, a raw material powder was prepared by mixing 80% of hexagonal zinc sulfide powder and 20% of niobium oxide powder. As the raw material powder, a slurry was produced by adding distilled water and an organic binder to a resin pot, and performing wet mixing using zirconia balls for 24 hours. After the obtained slurry was spray-dried and granulated, a compression molded body was obtained using a mold. This molded body was heated to 1100 ° C. at a rate of 3 ° C./min, and sintered in an Ar atmosphere for 3 hours to obtain a disc-shaped zinc sulfide-based sintered material having a diameter of 50 mm and a thickness of 5 mm. Further, this zinc sulfide-based sintered material was HIPed at a pressure of 2000 Pa and a temperature of 900 ° C. to increase the density. The density and surface resistance of this zinc sulfide-based sintered material were measured. The relative density was measured by the Archimedes method. Table 2 shows the obtained results.

The obtained sintered body was ground to a predetermined size with a diamond tool, a sputtering target was prepared in the same manner as in Example 2, and the same film formation evaluation as in Example 2 was performed.

Comparative Example 1 To a hexagonal zinc sulfide powder having an average particle size of 4 μm and a purity of 99.9%, 20% of silicon oxide powder having an average particle size of 10 μm and a purity of 99.9% was added, and a zirconia ball was added to a resin pot. Dry mixing was carried out for 24 hours. After granulation, the temperature was raised to 900 ° C. at a rate of 3 ° C./min by hot pressing, and in an Ar atmosphere,
Sintering was performed for 3 hours while pressing at a surface pressure of 250 kg / cm ² to produce a disc-shaped zinc sulfide-silicon oxide-based sintered material having a diameter of 50 mm and a thickness of 5 mm, and the density and surface resistance of the sintered body The value was measured. The relative density was measured by the Archimedes method. Table 2 shows the obtained results.

Using the obtained sintered body, a sputtering target was prepared in the same manner as in Example 2, and the same film formation evaluation as in Example 2 was performed.

[0050]

[Table 2]

[0051]

[Table 3]

From Tables 2 and 3 of the test results, Examples 2 and 3
All of the zinc sulfide-niobium oxide-based sintered materials of No. 3 showed a high compactness with the relative density of the sintered body being 90% or more. In addition, the zinc sulfide-silicon oxide based sintered material of Comparative Example 1 also exhibited a high compactness of 88%. However, with respect to the surface resistance value, a high conductivity of 0.8 Ω / □ was obtained in Example 2 and 0.9 Ω / □ was obtained in Example 3. Comparative Example 1 has a surface resistance of 10 ⁹ Ω / □ or more, indicating that the insulating property is high.

Regarding the sputtering rate, even if a thin film was formed under exactly the same conditions, the sputtering rate of Example 2 was lower than that of Comparative Example 1.
3, it was found that the sputtering rate could be increased by 20 to 50%, and a significant difference was obtained.

The zinc sulfide-silicon oxide based sintered material of Comparative Example 1 could not be formed at all by DC sputtering, but the zinc sulfide-niobium oxide based sintered material of Examples 2 and 3 was used. The film was formed by DC sputtering, and a sputtering rate twice as high as that of the RF sputtering method was obtained.

[0055]

According to the present invention, the zinc sulfide based sintered material according to the present invention is compared with 80 mol% ZnS-20 mol% SiO ₂ based sintered material.
Due to the high conductivity and low resistance, the thin film forming process that could only be performed by the RF sputtering method in the past has been
The C sputtering method is also possible, and the sputtering rate can be increased. By forming a thin film by this DC sputtering method, in a phase-change optical recording medium using a Te or Sb alloy recording layer, the production rate of the protective layer thin film can be increased. In addition, a large-sized sintered body can be manufactured.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of an optical recording medium including a phase-change recording layer and a protective layer in contact with the phase-change recording layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical recording medium 10 Disk substrate 2 Protective layer 3 Recording layer 4 Reflective layer

Continued on the front page (72) Inventor Yukio Noguchi 6F, Takeda Toba-cho, Fushimi-ku, Kyoto, Kyoto Prefecture F-term in Kyocera Corporation (reference) 4G030 AA20 AA56 BA15 GA11 GA24 GA27 GA29 4K029 AA09 AA24 BA18 BA43 BA51 BB01 BC08 BD12 CA05 DC05 DC09 5D121 AA04 EE09 EE11 EE14

Claims (9)

[Claims] 1. A zinc sulfide-based sintered material containing zinc sulfide as a main component and containing niobium oxide. 2. The zinc sulfide-based sintered material according to claim 1, wherein the content of niobium oxide is more than 5% by weight and not more than 50% by weight in terms of Nb ₂ O ₅ . 3. A composition comprising zinc sulfide as a main component and niobium oxide as N
A sputtering target comprising a zinc sulfide-based sintered material containing more than 5% by weight and not more than 50% by weight in terms of b ₂ O ₅ . 4. The content of niobium oxide is 10 to 50% by weight in terms of Nb ₂ O ₅ , and the surface resistance is 1%.
The sputtering target according to claim 3, wherein the sputtering target is 0 Ω / □ or less. 5. A raw material powder for forming a zinc sulfide-based sintered material, comprising: zinc sulfide powder having a particle size of 0.5 to 20 μm;
A raw material powder for a zinc sulfide-based sintered material, comprising a niobium oxide powder having an average particle size of 5 μm or less. 6. A mixture of zinc sulfide powder having an average particle size of 0.5 to 20 μm and niobium oxide powder having an average particle size of 5 μm or less is hot-pressed at a temperature of 800 to 1100 ° C. to form a sintered body. A method for producing a zinc sulfide-based sintered material. 7. A mixture of a zinc sulfide powder having an average particle size of 0.5 to 20 μm and a niobium oxide powder having an average particle size of 5 μm or less is formed into a desired shape, and the formed product is mixed with an inert gas at a temperature of 700 μm. A method for producing a zinc sulfide-based sintered material which is fired at a temperature of about 1200 ° C. to obtain a sintered body. 8. The content of niobium oxide in the mixture exceeds 5% by weight in terms of Nb ₂ O ₅ , and is 50% by weight.
The method for producing a zinc sulfide-based sintered material according to claim 6 or 7, wherein: 9. The method according to claim 7, wherein the zinc sulfide-based sintered material is
A method for producing a zinc sulfide-based sintered material that is subjected to hot isostatic pressing in a temperature range of 0 to 1200 ° C.