Samples of CaO-, MgO- or Y2O3-doped material were nitrided at temperatures of between 1400 and 2000C, in a graphite resistance furnace, under a N atmosphere. It was found that, depending upon the N and aliovalent oxide content, various types of ordered (-type) or disordered (tetragonal, cubic) phase could be observed. It was noted that nitridation of pure zirconia resulted in the formation of the ” phase. With increasing aliovalent oxide content, other -type phases became detectable. It was shown that the so-called effective total concentration of vacancies was the main factor which controlled transitions between phases.

M.Lerch, J.Wrba, J.Lerch: Journal of Solid State Chemistry, 1996, 125[1], 153-8