Effect of Nb2O5 content and sintering temperature on the microstructure and bending strength of porous Ni-YSZ cermets

Porous Ni-YSZ cermets are prepared by reducing NiO-YSZ composites upon exposure to (Ar+6% H2) gas. The porous cermets are prepared by the addition of carbon black (0.123 mol) to mixed NiO-YSZ powders and the conversion of NiO to Ni in the NiO-YSZ composites. The microstructure and bending strength of porous Ni-YSZ cermets as functions of sintering temperature and Nb2O5 content are discussed. The Ni-YSZ cermets consist of uniformly distributed Ni and YSZ grains as well as pores. Both higher sintering temperature and higher Nb2O5 content yield lower porosity, thus increasing the bending strength. The bending strength of 0.00470 mol% Nb2O5-containing Ni-YSZ cermets sintered at 1400 °C (111 MPa) is about two times higher than that of Nb2O5-free Ni-YSZ cermets sintered at 1400 °C (59 MPa).