Paracrystalline arrays of defect clusters, having some 5 times the lattice spacing of the average Co3-δO4 spinel structure, occurred in a more or less relaxed manner when sintered Co1-xO polycrystals were air-quenched below the Co1-xO/Co3-δO4 transition temperature in order to activate the oxy-precipitation of cube-like Co3-δO4 at dislocations. The same paracrystalline spacing was obtained for Co3-δO4 when formed by oxidizing/sintering the Co1-xO powders at 800C in air. This suggested a nearly constant δ-value for Co3-δO4 under the present temperature and PO2 conditions. The extra Co vacancies and Co3+ interstitials, as a result of the δ-value, could form additional 4:1-derived defect clusters for further paracrystalline distribution in the spinel lattice. The nanosize defect clusters self-assembled via columbic interaction and lattice relaxation.

Co3-δO4 Paracrystal - 3D Assembly of Nanosize Defect Clusters in Spinel Lattice. W.H.Lee, P.Shen: Journal of Solid State Chemistry, 2004, 177[1], 101-8