Preparation of transparent YAG ceramic and its application to window material of infrared spectrophotometer

Transparent polycrystalline YAG (Y3Al5O12) ceramic, optical characteristics of which are comparable to those of a single crystalline YAG, was fabricat ed by a sintering method using > 99.99 mass% purity powders and its applica tion to a window material of infrared spectrophotometer was investigated. I ts average grain size and pore density were 50 mu m and about 1 ppm, respec tively. It showed high strength (modulus of rupture: 350 MPa), high hardnes s (Vickers hardness [HV10]: 1280), low refractive index (1.8 at 590 nm wave length) and low thermal expansion coefficient (8 x 10(-6) K-1), and was ver y stable in various inorganic solvents, 10% HF solution, 1 M HCl solution, 1 M H2SO4 solution, 1 NI NaOH solution and 10% NH3 solution and organic sol vents, methyl alcohol, acetone, toluene and dimethyl sulfoxide. The transmi ttance of 1 mm-thick YAG was about 85% for the wavelength of <6 mu m and de creased with increasing wavelength to reach almost 0 % at 9 mu m. These res ults and some infrared spectral measurements indicate that the present YAG ceramic is a good window material in the range of 2.5 to 9 mu m.