Yttria (Y,O,) is a candidate for op

Yttria (Y,O,) is a candidate for optical applications, as it transmits at longer IR wavelengths than most other oxides (9.5-pn~ cutoff) and possesses superior thermal stability. Optical materials must be sintered to full density as even minimal residual porosity causes detrimental scattering. Commercially available yttria powders consist of particles that are irregular in shape and large in size, and therefore do not sinter to fully dense, uniform microstructures. Various processing techniques have been utilized to produce yttria powders that typically sinter better than the original raw material;' the processing emphasis was focused on the drying of the precipitate hydroxide precursors. While the powders obtained from these methods did not have uniform morphologies, they contained only soft and/or uniform agglomerates which resulted in improved sintered densities compared to traditional powders, implying that, while monodispersed, submicrometer equiaxed particles are certainly desired qualities, powder processing operations such as precipitation and drying techniques that influence agglomeration should not be overlooked in optimizing sinterability.