Preparation of Transparent YAG Ceramic and Its Application to Window Material of Infrared Spectrophotometer

Susumu NAKAYAMA*, Akio IKESUE* and Masatomi SAKAMOTO††

Department of Applied Chemistry and Biotechnology, Niihama National College of Technology; Yakumo-cho, Niihama-shi 792-8580 Japan
Research and Development Laboratory; Atsuta-ku, Nagoya-shi 456-8587 Japan
†† Department of Material and Biological Chemistry, Faculty of Science, Yamagata University; Kojirakawa-machi, Yamagata-shi 990-8560 Japan

Transparent polycrystalline YAG (Y3Al5O12) ceramic, optical characteristics of which are comparable to those of a single crystalline YAG, was fabricated by a sintering method using >99.99 mass% purity powders and its application to a window material of infrared spectrophotometer was investigated. Its average grain size and pore density were 50 μm and about 1 ppm, respectively. It showed high strength (modulus of rupture: 350 MPa), high hardness (Vickers hardness [HV10]: 1280), low refractive index (1.8 at 590 nm wavelength) and low thermal expansion coefficient (8×10−6 K−1), and was very stable in various inorganic solvents, 10% HF solution, 1 M HCl solution, 1 M H2SO4 solution, 1 M NaOH solution and 10% NH3 solution and organic solvents, methyl alcohol, acetone, toluene and dimethyl sulfoxide. The transmittance of 1 mm-thick YAG was about 85% for the wavelength of <6 μm and decreased with increasing wavelength to reach almost 0 % at 9 μm. These results and some infrared spectral measurements indicate that the present YAG ceramic is a good window material in the range of 2.5 to 9 μm.

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