The Size Induced Phase Transition in the Rb0.95NbxMo2−xO6.475–0.5x (x=1.31–1.663) Solid Solution with β‐Pyrochlore Structure

Abstract The size induced phase transition for non‐cubic β‐pyrochlore compounds Rb 0.95 Nb x Mo 2−x O 6.475–0.5x (x=1.31–1.663) has been studied in detail. The Rb 0.95 Nb x Mo 2−x O 6.475–0.5x (x=1.31–1.663) powders with different size particles have been prepared and investigated by X‐ray powder diffraction analysis and scanning electron microscopy with X‐ray microanalysis. The Rb 0.95 Nb 1.5 Mo 0.5 O 5.73 and Rb 0.95 Nb 1.375 Mo 0.625 O 5.79 powders consisted of ~20 μm crystals possess orthorhombic Pnma symmetry, whereas the same powders with particle size less 1 μm have cubic Fd‐3m and characterized by decreasing Rb content – Rb 0.7 Nb 1.5 Mo 0.5 O 5.58 and Rb 0.9 Nb 1.625 Mo 0.375 O 5.62 . The crystal structure of Rb 0.7 Nb 1.5 Mo 0.5 O 5.58 cubic phase refinement has been performed using the Rietveld method; and crystallographic reasons of structure reconstruction have been discussed. The electronic structure and band gap of Rb 0.95 Nb x Mo 2−x O 6.475–0.5x (x=1.31–1.663) compounds have been studied. Moreover the comparison of electronic structure for cubic and orthorhombic phases has been performed.