Structural investigations and luminescence of In2Ge2O7 and In2Si2O7

The crystal structures of the ordinary pressure forms of indium digermanate In₂Ge₂O₇ and disilicate In₂Si₂O₇ have been studied from X-ray powder diffraction data by Rietveld refinement. They are closely related to that of the thortveitite which crystallizes in the monoclinic system with the space group C2/m and Z = 2. They show luminescence properties below 160 K and 200 K respectively. The luminescence is discussed in terms of crystal structure and compared to that of some other luminescent indium oxides.