Influence of the powder preparation on the sintering of Yb-doped Sc2O3 transparent ceramics

We report the preparation and the sintering of high quality Yb:Sc2O3 powders with the ultimate intent to make transparent Yb:Sc2O3 ceramics for laser applications. The aim of the study is to compare two routes of powder preparation and observe the influence of the powder processing on the sintering of Yb-doped Sc2O3 ceramics. The powders were prepared (i) either from commercial oxides by a classical ceramic way (solid state reaction process) (ii) or by a wet chemical route. In that case, a carbonate precursor was synthesized by a coprecipitation method from a mixed solution of scandium and ytterbium nitrates using aqueous ammonium hydrogen carbonate as a precipitating agent. The Yb:Sc2O3 powder was obtained after heat treatment of the carbonate precursor at 700 C. The powders prepared by these two methods were characterized by BET measurements, XRD and SEM and their sintering behaviour was investigated by dilatometry. The effects of a grinding step and of the addition of a sintering aid addition (TEOS) were investigated. The microstructures of the vacuum sintered materials were observed by scanning electron microscopy. Electron probe microanalysis allowed to characterize the repartition of the dopant Yb3+ in the Sc2O3 matrix. Translucent ceramics with densities close to 99% were obtained in the best conditions.