Effect of Zr4+ and Y3+ dissolution on spinel formation from Co1-xO

Co1-xO (x similar to 0.01) powders mixed with yttria-partially stabilized zirconia (Y-PSZ) were sintered and annealed at 1600 degrees C for 1-100 h or 1300 degrees C for 300 h in air, and then characterized by analytical electron microscopy to investigate the effect of dopant on defect clustering and Co3O4 spinel formation above the Co1-xO/Co3O4 equilibrium temperature (900 degrees C). For all the fired composites, the spinel phase and its parent Co1-xO particles were found to contain the same amount of Zr4+ (<2 mol.%) and Y3+ (<1 mol.%). Both dopants have substituted for smaller Co2+ to generate charge- and volume- compensating defects and paracrystalline state of defect clusters. The (Zr,Y)-codoped spinel showed (111) faulting, presumably due to defect clusters of the zinc blende type with cation vacancies assembled along oxygen close packed (111) plane, making it feasible for crystallographic shear to occur.