JPH04202051A - Transparent ggg sintered body and its production - Google Patents

Abstract

PURPOSE:To obtain a transparent gadolinium-gallium garnet(GGG) sintered body suitable for use as an IR transmitting window material, etc., by hot- pressing high purity fine GGG powder in vacuum or in inert gas and subjecting the pressed body to hot isostatic pressing. CONSTITUTION:GGG powder having >=99.5% purity and >=3m<2>/g BET specific surface area is hot-pressed in vacuum or in inert gas at 1,200-1,720 deg.C under 100-500kg/cm<2> pressure to form a dense pressed body having >=95% theoretical density ratio and this pressed body is subjected to hot isostatic pressing at 1,500-1,720 deg.C under >=500kg/cm<2> pressure preferably with inert gas, gaseous oxygen or a mixture of them. The linear transmissivity of the resulting transparent GGG sintered body is >=70% in the visible and IR region of 0.4-3mum wavelength and >=75% in the IR region of 3-5mum wavelength in the case of 3mm thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a GGG sintered body with excellent translucency and a method for manufacturing the same.

[Conventional technology]

GGG (Gadolinium Gallium Garnet: G
dGa0 ) is a composite oxide consisting of gadolinium oxide (GdO) and gallium oxide (Gap), and is used as a substrate crystal for magnetic valve elements, and GGG doped with N(l) is a promising solid-state laser material. being watched.

Typically, GGG has a mole fraction of gallium oxide of 58.7 to 6.
In the range of 2.8 mol%, the crystal type becomes a single layer of cubic crystals (garnet structure), so it exhibits good light transmission without scattering at grain boundaries, and transmits light from wavelengths around 0.3 μm in the visible region. It is known that the properties of these materials increase rapidly, and that they exhibit uniform translucency up to a wavelength of around 3 to 5 μm in the infrared region.

However, since the use of GGG was limited to single crystal applications such as crystal substrate materials and solid-state laser materials as mentioned above, GGG has traditionally been
Although G single crystals have been produced, there have been almost no attempts to produce polycrystals from powder by a sintering method.

Furthermore, it is difficult to obtain large-sized products using single-crystal manufacturing methods such as the CZ method, and the product cost is high, so single-crystal GGG has not been used as an optical material such as visible and infrared transmitting windows. .

[Problem to be solved by the invention]

In view of such conventional circumstances, an object of the present invention is to provide a translucent GGG sintered body suitable as an infrared-transmitting window material, and a method for manufacturing the same.

[Means to solve the problem]

In order to achieve the above object, in the present invention, purity 99
．． It is made of polycrystalline GGG (gadolinium gallium garnet) with a thickness of 5% or more, and the in-line transmittance at a sample thickness of 3 is 70% or more in the visible and infrared wavelength regions of 0.4 to 3 μm, and in the red region of 3 to 5 μm. Translucency GG that is 75% or more in the outer area
A G sintered body is provided.

In addition, this method of manufacturing the translucent GGG sintered body has a purity of 99.
5% or more and specific surface area CBET value) 3rrVg or more GGG powder in vacuum or inert gas at a temperature of 1200 to 1720 C and a pressure of 100 to 500''97
Theoretical density ratio 95 by hot pressing at F, m2
% or more, and then subjected to HIP treatment at a temperature of 1500 to 1720 C and a pressure of 500 kgAm'' or more.

[Effect]

In the present invention, by hot pressing in vacuum or inert gas and subsequent H-P (hot isostatic pressing),
High purity and high density polycrystalline G without using sintering aids
It was found that a GG sintered body could be obtained.

Since this polycrystalline GGG sintered body has a cubic crystal type, there is little scattering at grain boundaries, and since it is highly pure and densely sintered, it can be used in the visible range to the infrared range. Extremely high translucency equivalent to that obtained can be obtained. That is, for a sample with a thickness of 3 mrn, which is a common thickness for optical materials, a straight line of 70% or more in the visible and infrared wavelength range of 0.4 to 3 μm, and 75% or more in the infrared region of 3 to 5 μm. The transmittance was obtained.

In the method of the present invention, the GGG powder used as a raw material for the GGG sintered body has a purity of 99.5% or more to prevent a decrease in translucency due to absorption of impurities, and in particular contains transition metal elements such as Fe. is not desirable. In addition, the primary particle size of the GGG powder is about 0.3 μm or less, that is, the specific surface area is 3 tri/g in BET value.

As mentioned above, it is necessary to preferably have a diameter of 7 to 15 φ'g or more in order to obtain a dense sintered body. As such a highly pure and fine GGG powder, a powder produced by alkoxide hydrolysis or coprecipitation method is suitable.

In the method of the present invention, the high-purity, high-density GGG powder as described above is sintered by hot pressing in vacuum or in an inert gas. The temperature in hot press sintering is 1200-17
20C and the pressure is 100 to 500kyΔm2.

Temperature less than 1200 r or pressure 100 kg/cm
If the temperature is less than 1,720°C, it is difficult to obtain a high-density sintered body with a theoretical density ratio of 95% or more.On the other hand, if the temperature exceeds 1720C, a liquid phase will occur, and light scattering will occur due to a deviation in the composition ratio and precipitation of a second phase. The factors increase, and at the same time, pores tend to remain in the grains,
This results in a significant decrease in translucency. Also, the hot press pressure is 5
If it exceeds 0 Q kg/cm2, it becomes difficult to use a normal graphite mold due to its strength, which is not preferable.

In the H-P treatment method following the above-mentioned hot press, 1500~
Since the sintered body is isotropically pressurized at a temperature of 1720C and a pressure of 500 kg/cm2 or more, pores in the sintered body are removed by plastic deformation and a diffusion mechanism. Therefore, the sintered body obtained by hot pressing in two directions (up and down) has a higher density, less distortion, and is optically uniform and has high light transmittance. In addition, if the theoretical density ratio of the sintered body obtained by hot pressing is less than 95%, most of the remaining pores become so-called open pores, and the high pressure gas used in the H process passes through these pores into the sintered body. Since it invades the inside, the densification by H-P does not proceed sufficiently.

The gas used in the HIP process is preferably an inert gas such as Ar, oxygen gas, or a mixed gas thereof. especially,
By mixing oxygen gas, it is possible to control the composition deviation caused by reduction of the sintered body during the H-P treatment, and there is an advantage that a decrease in translucency can be prevented.

〔Example〕

Example 1 High-purity GGG powder with a purity of 99.9% and a specific surface area of 54 g (BET value) was heated at 150 m
Hot pressing was carried out for 3 hours at a temperature of 0C and a pressure of 300 kv'cm2 to obtain a white sintered body with a theoretical density ratio of 99%.

This sintered body was placed in a H-P equipment and heated at 16°C using Ar gas.
A colorless and transparent sintered body was obtained by H-P treatment at a temperature of 50 C and a pressure of 2000 kg/cm'' for 2 hours.

Both sides of this GGG sintered body are mirror polished to a thickness of 3 m.
The sample was taken as m. When the in-line transmittance of this sample was measured using a spectrophotometer, the average transmittance was 78 in the wavelength range of 0.4 to 3 μm.
%, and showed excellent light transmittance of 81% on average in the 3-5 μm region.

Example 2 A white sintered body having a theoretical density ratio of 98% was obtained by hot pressing in the same manner as in Example 1 except that the same GGG powder as in Example 1 was used and the temperature was 1400C. Next, this sintered body was subjected to H-P treatment in the same manner as in Example 1, but at a temperature of 1600 C and for 3 hours to obtain a colorless and transparent sintered body.

The in-line transmittance measured in the same manner as in Example 1 for a sample with a thickness of 3 mm obtained by mirror-polishing both sides of the obtained GGG sintered body was 75% on average in the wavelength range of 0.4 to 3 μm. , and exhibited excellent light transmittance of 78% on average in the 3-5 μm region.

Example 3 Purity 99.9%, specific surface area 10 rrl/g (BI
High-purity GGG powder with a T value of
Hot pressing was carried out for 3 hours at a temperature of C and a pressure of 500 Jc9Am'' to obtain a white sintered body with a theoretical density ratio of 96%.

This sintered body was placed in a H-P apparatus and subjected to H-P treatment using Ar-1%0 gas at a temperature of 1520 C and a pressure of 2000 ky/Cm2 for 8 hours to obtain a colorless and transparent sintered body. .

For a sample with a thickness of 3 am obtained by mirror polishing both sides of the obtained GGG sintered body, the in-line transmittance measured in the same manner as in Example 1 was 70% on average in the wavelength range of 0.4 to 3 μm.
, and exhibited excellent light transmittance of 75% on average in the 3-5 μm region.

〔Effect of the invention〕

According to the present invention, a translucent G having high purity and high density and excellent in-line transmittance in the visible and infrared regions can be used.
We can provide GG sintered bodies.

This translucent GGG sintered body is particularly useful as an optical material for visible or infrared transparent windows having a thickness of 3 mm or more.

Claims (3)

[Claims] (1) Made of polycrystalline GGG (gadolinium gallium garnet) with a purity of 99.5% or more, sample thickness 3 mm
1. A translucent GGG sintered body having a linear transmittance of 70% or more in the visible and infrared wavelength regions of 0.4 to 3 μm and 75% or more in the infrared region of 3 to 5 μm. (2) Purity 99.5% or more and specific surface area (BET value) 3
GGG (gadolinium gallium garnet) powder of m^2/g or more is heated in vacuum or inert gas at a temperature of 1200 to 1720°C and a pressure of 100 to 500 kg/g.
Theoretical density ratio is 95 by hot pressing at cm^2.
% or more, and then subjected to HIP treatment at a temperature of 1500 to 1720°C and a pressure of 500 kg/cm^2 or more. (3) A translucent G characterized by using an inert gas, oxygen gas, or a mixed gas thereof for HIP treatment.
Method for manufacturing GG sintered body.