The Crystal Structure, Vibrational Spectra, and Thermal Behavior of Piperazinium(2 +) Selenate Monohydrate and N, N-Dimethylpiperazinium(2+) Selenate Dihydrate

The structures of several Ga2O3-In2O3-SnO2 phases were investigated using high-resolution electron microscopy, X-ray diffraction, and Rietveld analysis of time-offlight neutron diffraction data. The phases, expressed as Ga4-4xIn4xSnn-4O2n-2 (n=6 and 7 -17, odd), are intergrowths between the beta-gallia structure of (Ga,In)2O3 and the rutile structure of SnO2. Samples prepared with ngreater-than9 crystallize in C2/m and are isostructural with intergrowths in the Ga2O3-TiO2 system. Samples prepared with n=6 and n=7 are members of an alternative intergrowth series that crystallizes in P2/m. Both intergrowth series are similar in that their members possess 1-D tunnels along the b axis. The difference between the two series is described in terms of different crystallographic shear plane operations (CSP) on the parent rutile structure.