Powder diffraction studies of SrNb2O6 and SrNb6O16

Abstract

The crystal structure of the monoclinic modification of SrNb2O6 was studied with Guinier-Hägg X-ray powder diffraction data. The cell dimensions are a = 7.7223(7) Å, b = 5.5944(5) Å, c = 10.9862(7) Å and β = 90.372(5)°. The space group is P21/c. The structure was refined by the Rietveld full-profile technique. A comparison was made with the isostructural orthorhombic CaTa2O6. An orthorhombic strontium/niobium oxide with unit cell dimensions a = 3.9563(3) Å, b = 10.1889(8) Å and c = 14.794(1) Å was studied with Guinier-Hägg data from a mixed pattern. It is shown that the compound is isostructural with NaNb6O15F and has the composition SrNb6O16.