Combustion synthesis of nanocrystalline yttria: Tailoring of powder properties

Nanocrystalline yttria powders were synthesized by the combustion technique, using glycine as the fuel. The effect of oxidant-to-fuel ratio on powder characteristics was investigated. The yttria powders obtained were characterized by powder X-ray diffraction for phase purity. In situ agglomeration behavior was studied by high temperature-X-ray diffraction. The best powder properties were observed for the powders with glycine-to-nitrate ratio of 1:1. This product has a crystallite size of about 8 nm and a high surface area of about 165 m2/g after calcination at 600 °C. The sintered density obtained for this powder was about 97% of the theoretical density. The sintered microstructure as studied by scanning electron microscopy, revealed the presence of fine grains. The size of the primary crystallites was investigated by transmission electron microscopy. The surface area and the sintering behavior was also studied for powders prepared using different oxidant-to-fuel ratios and the results showed a remarkable correlation between the different fuel contents and the powder properties.