Powder samples of N1-xO, where x was less than 0.001, were studied in the pure state or when mixed with pure ZrO2 or partially yttria-stabilized ZrO2. The materials were sintered, and were then annealed (1573 or 1873K, up to 300h) in order to investigate the dopant-dependence of defect clustering. Transmission electron microscopic observations, and energy X-ray analysis, indicated that the dissolution of Zr4+ (about 2mol%, with or without up to 0.3mol%Y3+) but not Ni3+ caused defect-clustering. The latter was more rapid at 1873 than at 1573K, and preferred to nucleate at interfaces and dislocations. The paracrystalline distribution of defects was found to be almost 3.5 and 2.5 times the lattice parameter of N1-xO, for Zr-doped and (Zr,Y)-doped N1-xO, respectively. The predominantly Zr4+ dissolved cations, in octahedral sites with charge- and volume-compensating Ni and O vacancies (that is, ZroctnO6-mm), could create local domains from which Ni3+ was expected to be expelled.

Defect Clusters and Superstructures of Zr4+ Dissolved Ni1-xO. J.Chen, P.Shen: Journal of Solid State Chemistry, 1998, 140[2], 361-70