Synthesis of nanocrystalline yttria powder and fabrication of Cr,Nd: YAG transparent ceramics

Nanocrystalline yttria powders were synthesized by a precipitation method from yttrium nitrate solution using ammonia water as a precipitant. It was found that the addition of small amount of ammonia sulfate in yttrium nitrate solution can reduce the agglomeration of the produced yttria powders. Y2O3 powder with an average particle size of 67 nm was obtained by calcining the precursor at 1100 degrees C for 2 h. Transparent 0.1 at.% Cr, 1.0 at.% Nd:YAG ceramics were fabricated by a solid-state reaction and vacuum sintering with CaO as a charge compensator and tetraethyl orthosilicate (TEOS) as a sintering aid using the prepared Y2O3, and the high-purity commercial powders of alpha-Al2O3, Nd2O3 and Cr2O3 as raw materials. Fully dense Cr, Nd:YAG ceramic with some secondary phase of alumina was obtained by sintering at 1750 degrees C for 10 h. The average grain size of the sample was about 10 mu m and the in-line transmittance was similar to 52% at 1064 nm, which is lower than the transmission (similar to 82%) of the sample from all-commercial oxide powders. The low transmittance of Cr, Nd: YAG ceramic is mainly caused by the formation of secondary phase due to the non-stoichiometry of the starting powders. In order to overcome the current limitations of the study, weight loss cause by the decomposition of SO42- ions and the absorption of water or organic materials in yttria nanopowder should be taken into account. (C) 2011 Elsevier B. V. All rights reserved.