A cubic calcium oxynitrido-silicate, Ca2.89Si2N1.76O4.24

Abstract

The title compound, tricalcium oxynitride silicate, with composition Ca3-xSi2N2-2xO4+2x (x ≃ 0.12), is a perovskite-related calcium oxynitrido silicate containing isolated oxynitrido silicate 12-rings. The N atoms are statistically disordered with O atoms (occupancy ratio N:O = 0.88:0.12) and occupy the bridging positions in the 12 ring oxynitrido silicate anion, while the remaining O atoms are located at the terminal positions of the Si(O,N)4 tetrahedra. The majority of the Ca2+ cations fill the channels along [100] in the packing of the 12-ring anions. The rest of these cations are located at several positions, with partial occupancy, in channels along the body diagonals.