(Sr1–xCax)(11+16y–25z)/2(Si1–yAly)16(N1–zOz)25 (x ≈ 0.24, y ≈ 0.18, z ≈ 0.19) – A Novel Sialon with a Highly Condensed Silicate Framework

Abstract

Abstract(Sr1–xCax)(11+16y–25z)/2(Si1–yAly)16(N1–zOz)25 (x ≈ 0.24, y ≈ 0.18, z ≈ 0.19) was obtained by high‐temperature synthesis (1650 °C – 1700 °C) using CaSiAlN3, Si3N4, AlN, SiO2, and Sr2N as starting materials. The crystal structure [Imm2 (no. 44), a = 20.6973(6), b = 10.7292(4), c = 4.8881(2) Å, Z = 2, R1 = 0.0326, wR2 = 0.0735] was determined from single‐crystal X‐ray data using dual space methods and confirmed for the bulk material by Rietveld refinement on X‐ray powder diffraction data. The structural results are corroborated by lattice energy calculations (MAPLE). The compound is the first representative of a novel silicate framework. The anionic part of the structure is built up from highly‐condensed dreier ring layers extending parallel (100), which are interconnected by common N and O atoms. In the resulting voids of this framework, there are three different cation sites, which are coordinated by six, eight, and twelve nitrogen and oxygen atoms, respectively. The largest one is fully occupied by Sr atoms, whereas the other two sites host Sr and Ca atoms or vacancies, respectively.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)