Silicates and Perovskites: Two Themes with Variations.

An intermediate position between oxosilicates and nitridosilicates on one side and silicates and silicon oxo salts on the other is taken up by Ce Si O N . This compound is a perovskite derivative in which the octahedrally coordinated cations have been extensively replaced by tetrahedrally coordinated cations to give the formula Ce (Si Si □)(O N □ ) ( =coordination number, □=lattice vacancy). The presence of vacancies in both the cation and the anion sublattices leads to expectations of ionic conductivity.