Sr3(Al3+xSi13−x)(N21−xO2+x):Eu2+(x ∼ 0): a monoclinic modification of Sr-sialon

Abstract

The structure of the title compound, Sr-bearing oxonitridoaluminosilicate (Sr-sialon), contains two types of channels running along the a axis, with the three unique Sr atoms (coordinatioon number seven) residing in the larger one. The channels cross a three-dimensional Si–Al–O–N network, in which the Si and Al atoms are in a tetrahedral coordination with N and O atoms. The chemical composition of the crystal is close to Sr3Al3Si13N21O2 (tristrontium trialuminium tridecasilicon henicosanitride dioxide), which can be expressed as a mixture of SrSiN2, Si3N4, AlN, and SiO2 components in the molar ratio 3:3:3:1. The crystal studied was metrically orthorhombic, consisting of four twin components related by metric merohedry.