On the solid solution of the spinel phase in the system NiO–Al2O3

The solid solubility of Al2O3 in NiAl2O4 spinel has been investigated by powder X-ray diffraction of samples prepared by solid state synthesis. The solid solution region found was in agreement with a previous report. The cubic cell parameter of the spinel solid solution was observed to decrease with increasing alumina content. Spinel with high alumina content was shown to be close to an inverse spinel as previously reported for stoichiometric NiAl2O4 and the inversion parameter proved to be relatively independent of the overall composition.