A new CeO₂ form obtained as oxidation product of CeO₂+SiO₂-doped hot-pressed silicon nitride

By using data from the Wallace & Ward [J. Appl. Cryst. (1975), 8, 255-260] cylindrical texture camera integrated with other traditional X-ray powder film techniques for very low and very high diffraction angles, a new high-temperature modification of CeO₂ was identified and indexed resulting in a trigonal or hexagonal unit cell with a = 8.36(2) and c = 10.42(2) Å, (axial ratio 1.264) and Z = 16. The new phase is an oxidation product of CeO₂-doped hot-pressed silicon nitride. It can be quenched to room temperature under appropriate conditions. Its stability on reheating is strictly related to its interaction with the silicate phase.