Characterization of SnNbO_4+x with Cation Ordered Fluorite and α-PbO₂ Related Structures Prepared by Oxidation of Sn₂Nb₂O₇ Pyrochlore

抄録

Two kinds of metastable phases with a nominal composition of SnNbO_4+x, in which the Sn and Nb ions are respectively ordered, have been prepared by oxidation of pyrochlore type precursor with a nominal composition of Sn₂Nb₂O₇. The one was a fluorite related α-CeZrO₄ type SnNbO_4+x, which was prepared by oxidation of the precursor in 1%Ar/O₂ at 673 K for 120 h. The other was a α-PbO₂ related type SnNbO_4+x, which was prepared by oxidation of the precursor in O₂ at 723 K for 120 h. Chemical compositions and oxidation states of cations for the two metastable phases were determined by ICP and TG analysis and ¹¹⁹Sn Mossbauer and Sn 4d and Nb 3d x-ray photoemission spectroscopies. Infrared absorption and Raman spectra of the phases have been reported.