Fabrication of yttrium aluminum garnet transparent ceramics from yttria nanopowders synthesized by carbonate precipitation

Nanocrystalline yttria powders have been successfully synthesized by using yttrium nitrate as starting salt and ammonium hydrogen carbonate as precipitant. It was found that a small amount of ammonia sulfate in the yttrium nitrate solution can effectively reduce the agglomeration and the resultant powders display good dispersion. Pure cubic phase yttria powders were prepared by calcining the precipitate at 1100 °C for 4 h. The size of the as-prepared yttria powders was about 60 nm in diameter and showed excellent sintering activity. The as-prepared yttria nanopowders and commercial ultrafine alumina powders were used to fabricate YAG ceramics by solid-state reaction method and transparent YAG ceramics have been obtained by vacuum sintering at 1760 °C for 6 h.