Synthesis of ultrafine NiO/8YSZ composite powders

Ultrafine NiO/8YSZ (8 mol% Yttria-Stabilized Zirconia) composite powders were prepared by using a glycine nitrate process (GNP) for anode material of solid oxide fuel cells. The specific surface areas of synthesized NiO/8YSZ composite powders were examined with controlling pH of a precursor solution and the content of glycine. The binding of glycine with metal ions occurring in the precursor solution was analyzed by using FTIR. The characteristics of synthesized composite powders were examined with X-ray diffractometer, a BET method with N₂ absorption, scanning and transmission electron microscopies. Ultrafine NiO/8YSZ composite powders of 15-18 m²/g were produced through the GNP when the content of glycine was controlled to 1 to 2 times of the stoichiometric ratio in the precursor solution. Strongly acid precursor solution increased the specific surface area of the synthesized composite powders. This is suggested to be caused by the increased binding of metal ions and glycine under strong acid solution of pH=0.5 that lets glycine of mainly the amine group of NH₃ ^-. After sintering and reducing treatment of NiO/8YSZ composite powders synthesized by GNP, the Ni/8YSZ pellet showed ideal microstructure: very fine Ni particles of 3-5 μm were distributed uniformly and fine pores around Ni metal particles were formed, thus, leading to an increase of the triple phase boundary among gas, Ni and 8YSZ