Improved microstructure and optical properties of Nd:YAG ceramics by hot isostatic pressing

Hot isostatic pressing (HIP) has unique advantages in the preparation of high-density, fine-grained ceramics. In this work, 1.0 at.% neodymium-doped yttrium aluminum garnet (Nd:YAG) powders were prepared via solid-state reaction (SSR) and co-precipitation (CP) methods, and differences in their microstructure after being subjected to the same sintering process were compared. After calcination of raw materials at different temperatures, there was significant phase change at 800 degrees C-1400 degrees C for SSR powders. However, this process did not occur for CP powders. Average grain size of Nd:YAG ceramics prepared via CP method was smaller than that of ceramics prepared via SSR method. HIP provided significant improvement in both microstructure and in-line transmittance of ceramics. Ceramics pre-fired under vacuum at 1700 degrees C showed slight increase in grain size after HIP, with densities close to 100%, and clean, narrow grain boundaries. Moreover, in-line transmittance of ceramics increased from 69.91% to 80.37% (at 1064 nm) via HIP.