The defect chemistry of the oxide was studied by means of X-ray powder diffractometry, and Rietveld fitting. This provided further evidence for the role which was played by the singly-charged anionic species, O-. The Rietveld fitting of powder profiles indicated lower R-factors when this species was present. The analysis was confirmed by performing calculations, of d-spacings, which allowed for the presence of Ni3+ (the more common defect species) and O-.

A.Norman, C.Murphy, M.A.Morris: Key Engineering Materials, 1996, 118-119, 139-46