Conversion into single-phase YAG ceramics at low temperature by stoichiometry adjustment

In the case of low-temperature fabrication aiming at transparent polycrystalline YAG ceramics with fine grain size, it is easy to retain trace amounts of the intermediate YAP phase, thereby reducing the optical transmittance. To address this issue, adding a small amount of Al2O3 to the starting YAG powder was found to promote the transformation of the residual YAP phase to the YAG phase at low temperatures. The study investigated the effect of sintering temperature and excess Al2O3 amount on preparing transparent YAG ceramics by hot pressing. The transmittance of the Al2O3-aided single-phase YAG ceramic (2 mm thick) prepared using the two-step sintering reached 43.4 % at 400 nm and 71.8 % at 1064 nm, with a grain size of about 2 mu m, while the transmittance of the multiphase YAG ceramic without Al2O3 addition was less than 1 % at both wavelengths.