Abstract
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 >99.99mass% purity powders and its application to a window material of infrared spectrophotometer was investigated. Its average grain size and pore density were 50μm and about 1ppm, respectively. It showed high strength(modulus of rupture: 350MPa), high hardness(Vickers hardness [HV10]: 1280), low refractive index(1.8 at 590nm wavelength) and low thermal expansion coefficient(8×10-6K-1), and was very stable in various inorganic solvents, 10% HF solution, 1M HCl solution, 1M H2SO4 solution, 1M 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 <6μm and decreased with increasing wavelength to reach almost 0% at 9μm. 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 9μm.
