Synthesis, crystal structure, and anisotropic thermal expansion of Dy_4.67(SiO₄)₃O

A new phase in the Dy–Si–O system, Dy_4.67(SiO₄)₃O, was prepared in powderform using the mixed oxide method. Dy_4.67(SiO₄)₃O was first observed at 1300 °C, and phase purity was achieved after 96 h at 1600 °C. 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 groupP6₃/manda=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 °C, providing the axial and cell volume expansion.