JPH05235462A - Fabrication of polycrystalline transparent yag ceramic for solid laser - Google Patents

Abstract

PURPOSE:To obtain a high density transparent sintered structure including a lasing function added thereto by employing Al2O3 and Y2O3 powder with proper impurity and of a specific surface area, and adding lanthanide elements excepting Ce and components of Cr, Ti to the powder, and further synthesizing them under proper conditions. CONSTITUTION:There is mechanically blended a composition which is yielded by adding one kind or a plurality of kinds of Cr Ti and lanthanide elements excluding Ce to Al2O3 and Y2O3 powder with 99.9% by weight or more purity and 1-5m<2>/g and 5-100m<2>/g specific surface areas. The composition is then dried and molded under ordinary pressure or reduced pressure, and is further burned at a temperature of 1600-1850 deg.C after being molded. In this case, addition of 50-10000ppm SiO2 component as a sintering auxiliary promotes removal of matter exhibiting optical anisotropy to shorten burning time. Hereby, there is synthesized transparent YAG ceramic possessing substantially the same optical properties as that of a single crystal with a relatively simplified process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a garnet structure suitable for use as a laser oscillator and has a chemical formula of Y ₃
It relates to the production of clarified yttrium aluminum garnet ceramics (YAG) represented as Al ₅ O ₁₂ .

[0002]

2. Description of the Related Art YAG is a laser produced by adding lanthanide ions such as Nd ³⁺ and Ho ³⁺ as ions involved in light emission and single crystallizing by the Czochralski method, floating zone method or Bridgman method. It becomes possible to oscillate light.

Since the YAG laser has a different oscillation wavelength depending on the added ions and a high output laser beam can be obtained, it is possible to cut, weld, anneal a fiber branching light source or various materials, or perform wavelength conversion using an SHG element in recent years. Microfabrication and the use of laser scalpels are used.

When synthesizing a single crystal, the apparatus for growing the single crystal and the iridium crucible used for the growth are extremely expensive, the growth temperature is required to be about 2000 ° C., and the growth rate is 0.2 to 0. It is extremely slow at 3 mm / hr, it takes too much manufacturing cost and manufacturing time, only one single crystal rod can be obtained for one device, and the productivity is low, and the diameter of the single crystal rod is as small as around 50 mm. There are various problems such as the fact that the concentration of the added ions cannot be increased to 1 atom% or more because the segregation of the added ions occurs.

Recently, methods for synthesizing transparent YAG ceramics have been described in, for example, JP-A-1-264963 and JP-A-2-283663, but these do not synthesize a composite powder by a complicated wet method. However, there is a problem in terms of manufacturing cost.

[0006]

The problem to be solved by the present invention is to find a means for relatively easily producing transparent YAG ceramics to which various laser emitting elements are added.

[0007]

The method for synthesizing transparent YAG ceramics according to the present invention has a purity of 99.9% by weight or more and a specific surface area of 1 to 50 m ² / g and 5 respectively.
Al ₂ O ₃ and Y ₂ O ₃ powders of up to 100 m ² / g are weighed so as to be in the vicinity of the YAG composition, and lanthanide elements other than Ce and Cr and Ti element components are added thereto, and simple mechanical mixing is performed. After kneading by treatment, the product is molded as desired by a uniaxial or isotropic pressure press or the like, and this molded product is further fired in oxygen or hydrogen gas at 1600 to 1850 ° C. or in a vacuum having 10 ⁻¹ Torr or more. By doing so, the above object was achieved.

[0008]

The present invention is based on Al ₂ O having proper purity and specific surface area.
₃ , Y ₂ O ₃ powder is used, lanthanide elements other than Ce, Cr, and Ti element components are added, and synthesis is performed under appropriate conditions to achieve transparent high-density sintering with a laser oscillation function. The body can be obtained, and a large ceramic laser can be industrially manufactured at low cost.

The synthesis process of the respective raw material powders of Al ₂ O ₃ and Y ₂ O ₃ used in the present invention is not particularly limited, but sinterability, that is, the viewpoint of low temperature sintering and the viewpoint of reaction sintering. From the viewpoint, it is desirable that the material should be easily sintered and have a large specific surface area.

Al ₂ O ₃ and Y ₂ O ₃ powders are weighed to a YAG composition. At this time, a part of Y ₂ O ₃ is replaced when the lanthanide element component other than Ce is added, and a part of Al ₂ O ₃ is replaced when the Cr and Ti element components are added.
Upon addition, salts such as sulfates and nitrates, alkoxides and oxide powders can be used, but the addition method applied is not particularly limited. An organic solvent such as alcohol or distilled water is added to this mixture and mixed in a pot mill. The mixed powder is dried under reduced pressure or normal pressure. The obtained uniform mixed powder is molded into a predetermined shape by a uniaxial press, a cold isostatic press or the like. Then, by firing at a temperature of 1600 to 1850 ° C. for 5 to 100 hours in oxygen gas, hydrogen gas, or vacuum, high density YAG ceramics having high transparency can be obtained.

In the present invention, the starting material Al is used during sintering.
Sintering proceeds while the ₂ O ₃ and Y ₂ O ₃ powders react with each other, but Y ₄ Al ₂ O ₉ is first produced and then YAl
O ₃ is produced, and then this YAlO ₃ remains Al ₂
It reacts with O ₃ and finally becomes YAG. When the reactivity of the powder used is low in this sintering process, optically anisotropic YAlO ₃ remains until the final stage of sintering, which significantly reduces the transparency of the sintered body. In the present invention, especially Y ₂
It has been found that the reactivity of the O ₃ powder is important, and it is preferable to set the specific surface area of the Y ₂ O ₃ powder to be applied to about 2 times or more that of Al ₂ O ₃ .

When adding a SiO ₂ component as a sintering aid, salts such as sulfates and nitrates, alkoxides,
The SiO ₂ powder itself can be used, but the addition method applied is not particularly limited. SiO ₂ is
The particles in the sintered body are slightly grown, and at the same time, the effect of accelerating the removal of the above-mentioned substance exhibiting optical anisotropy can be obtained. By adding SiO ₂ , the firing time can be shortened. Si
Since the ions can be replaced with Al ions, they do not exist as foreign matters in the sintered body, and therefore do not become a factor that deteriorates the optical characteristics. However, when a predetermined amount or more is added, SiO ₂ is precipitated in the grain boundaries, or abnormal grain growth is caused to form a nonuniform structure, which becomes a factor of deteriorating the optical properties. Further, when the amount of SiO ₂ is small, the effect cannot be sufficiently exhibited, and the amount is limited to a specific range.

[0013]

EXAMPLE 100 g of Al ₂ O ₃ and Y ₂ O ₃ powders were weighed in total, and each powder and ethyl alcohol 300 cc were put into a pot mill, and further, alumina ball 500 was used.
g and mixed for 24 hours. 500m of mixed powder
It was dried under reduced pressure of mHg and the dried powder was lightly remixed in a mortar.

This powder was preliminarily molded into a tablet having a diameter of 50 mm and a height of 15 mm, and then molded by a rubber press at a molding pressure of 10 mm.
It was molded at 00 kg / cm ² .

This molded body was placed in an electric furnace and heated at 100 ° C./h.
The temperature is raised at r, and after firing at a predetermined temperature for 5 hours, 100 ° C./h
Cooled at r. The obtained sintered body has a diameter of 15 mm and a thickness of 1
It processed into the sample of mm. Both surfaces of the sample were mirror-finished with 1 μm diamond paste.

Examples 1 to 19 shown in Table 1 have a purity of 99.
The composition ratio of 99% by weight of Al ₂ O ₃ and Y ₂ O ₃ powder is 4
2.9: 57.1 (that is, the molar ratio is 5: 3), and the amount of Al ₂ O ₃ and Y ₂ O ₃ is adjusted by the addition amounts of R, Cr, and Ti elemental components. Al
The specific surface area of ₂ O ₃ and Y ₂ O ₃ powder is _{2 to} 50 m, respectively.
² / g, varied in the range of 5 to 100 m ² / g,
Furthermore, the results of changing the sintering temperature from 1600 to 1800 ° C. are shown. Although only Nd is described here as the R, Cr, and Ti elements, similar results were obtained with other additive substances.

[0017]

[Table 1] In Examples 20 to 31 shown in Table 2, the specific surface areas of Al ₂ O ₃ and Y ₂ O ₃ powders each having a purity of 99.99% by weight were fixed to 8 m ² / g and 25 m ² / g. The results obtained by adding the same R, Cr, and Ti elemental components to those described above, further adding SiO ₂ as a sintering aid, and firing in vacuum are shown below.

[0018]

[Table 2] Comparative Example A commercially available Nd: YAG (0.6 at%) single crystal was cut into the same sample size, and after double-side polishing, the transmittance was measured. As a result, the transmittance at a wavelength of 700 nm was 80%.

Comparative Examples 1 to 9 shown in Table 3 are commercially available Al ₂
O ₃ , Y ₂ O ₃ powder (specific surface area 0.5 m ² / g, 2 m ²
/ G), or Al ₂ O ₃ or Y
_One of the powders of ₂ O ₃ is outside the scope of claims,
Furthermore, the results of adding SiO ₂ within the scope of the claims to this are shown. Furthermore, Al within the scope of claims
The results obtained when SiO ₂ was added to the ₂ O ₃ and Y ₂ O ₃ powders in amounts not included in the claims are shown.

[0020]

[Table 3] When a powder with a small specific surface area is used, or when one of the powders has a specific surface area outside the scope of the claims, the reactivity of the powder is low, so that optical anisotropy in the sintered body There are many phases shown, which results in low transmittance. Further, even if SiO ₂ within the scope of the claims is added to this composition, no improvement in transmittance is observed. Further, when the amount of SiO ₂ added was 50 ppm or less, no effect of promoting sintering was observed, and conversely, when the amount added was large, abnormal grain growth occurred and the transmittance became low.

[0021]

According to the present invention, the following effects can be obtained.

(1) No need for powder synthesis by a complicated and costly wet method such as alkoxide or coprecipitation method, and a transparent material having almost the same optical characteristics as a single crystal by a relatively simple process. It is possible to synthesize YAG ceramics.

(2) The obtained transparent YAG ceramics to which various elements are added is preferably used as a laser oscillation small rod.

(3) Since the obtained transparent YAG ceramics to which various elements are added can have a high concentration of elements contributing to laser oscillation as compared with the conventional single crystal, a high-power laser is produced. Can be oscillated and can be made smaller than the conventional single crystal.

(4) Since the manufacturing method itself can be synthesized by a ceramic technology different from the conventional one, the manufacturing cost can be significantly reduced, the manufacturing process can be significantly shortened, and further, a large rod or slab can be manufactured.

Claims (2)

[Claims] [Claim 1] Each of the specific surface area at a purity of 99.9% by weight or more 1 to 50 m ² / g and 5 to 100 m ² / g of A
A mixture obtained by adding 1 (or more) of R (R is a lanthanide element other than Ce), Cr, and Ti element to 1 ₂ O ₃ and Y ₂ O ₃ powder is kneaded by mechanical mixing and subjected to normal pressure or reduced pressure. A method for producing transparent yttrium-aluminum-garnet-ceramics, which comprises drying and molding below, and then firing at a temperature of 1600 to 1850 ° C. 2. The method for producing transparent yttrium aluminum garnet ceramics according to claim 1, wherein a SiO ₂ component is added as a sintering aid in a range of 50 to 10,000 ppm.