Transparency and Photoluminescence of Gas-Pressure Sintered Lu-α-SiAlON:Ce3+ Ceramics

Owing to the growing demand for high power optical devices in several fields such as manufacturing, medicine, and communications, the demand for large and transparent inorganic materials capable of emitting multiple colors is increasing. alpha-SiAlON, which has excellent thermal and mechanical properties, is a phosphor that emits blue light because of the doping of Ce3+. However, only a few transparent and photoluminescent alpha-SiAlON:Ce3+ ceramics have been developed. In this study, we fabricated transparent alpha-SiAlON:Ce3+ ceramics using a gas-pressure sintering technique utilizing Lu3+, which has the smallest ionic radius among the rare-earth ions used to stabilize alpha-SiAlON. The Lu-alpha-SiAlON:Ce3+ ceramics exhibited higher transparency than Y-alpha-SiAlON:Ce3+ because of their finer grain size. The maximum emission wavelength of the Lu-alpha-SiAlON:Ce3+ ceramics was blue shifted relative to that of the Y-alpha-SiAlON:Ce3+ ceramics owing to lattice shrinkage. A lower Ce concentration resulted in higher transparency and a blue shift in the maximum emission wavelength. Furthermore, the in-line transmittance of the gas-pressure sintered Lu-alpha-SiAlON:Ce3+ ceramics using fine raw powders of rare-earth oxides was 50% at 600 nm, which was higher than that of Y-alpha-SiAlON:Ce3+ ceramics prepared via the same gas-pressure sintering technique followed by hot isostatic pressing.