Synthesis, crystal structure, and anisotropic thermal expansion of Dy4.67(SiO4)3O

A new phase in the Dy-Si-O system, Dy-4.67(SiO4)(3)O, was prepared in powder form using the mixed oxide method. Dy-4.67(SiO4)(3)O was first observed at 1300 degreesC, and phase purity was achieved after 96 h at 1600 degreesC. The crystal structure was determined using single crystal diffraction using synchrotron radiation, and powder x-ray diffraction data was refined using the Rietveld method. The structure was found to be apatite-type, hexagonal, with space group P6(3)/m and a = b = 0.93883(2) nm, c = 0.67820(1) nm, Z = 2. High-temperature x-ray powder diffraction was used to characterize the anisotropic thermal expansion over the temperature range of 24-1450 degreesC, providing the axial and cell volume expansion.