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

Abstract

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. Y 2O 3 powder with an average particle size of 67 nm was obtained by calcining the precursor at 1100 °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 Y 2O 3, and the high-purity commercial powders of α-Al 2O 3, Nd 2O 3 and Cr 2O 3 as raw materials. Fully dense Cr,Nd:YAG ceramic with some secondary phase of alumina was obtained by sintering at 1750 °C for 10 h. The average grain size of the sample was about 10 μm and the in-line transmittance was ∼52% at 1064 nm, which is lower than the transmission (∼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 SO 4 2− ions and the absorption of water or organic materials in yttria nanopowder should be taken into account.