Hochdrucksynthese und Strukturverfeinerung von Strontium-Danburit, SrB2Si2O8

Abstract

Abstract Single crystals of strontium danburite, SrB2Si2O8, were found after high-pressure treatment of SrSiO3/SiO2/Al2O3 mixtures at 40 kbar and 1400°C, obviously formed by an unwanted side reaction with the boron oxide-containing boron nitride capsules used. The crystals are orthorhombic, space group Pnma, with a = 8.1891 (5), b = 7.9311 (6), c = 8.9284(5) Å and Z = 4. The structure was refined to R = 0.031, Rw = 0.028 for 590 independent, absorption-corrected reflections. SrB2Si2O8 is isostructural with danburite (CaB2Si2O8). The structure comprises a tetrahedral framework of ordered B2O7 and Si2O7 groups which contains Sr in irregular coordination.