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

The size induced phase transition for non-cubic beta-pyrochlore compounds Rb0.95NbxMo2-xO6.475-0.5x (x=1.31-1.663) has been studied in detail. The Rb0.95NbxMo2-xO6.475-0.5x (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 Rb0.95Nb1.5Mo0.5O5.73 and Rb0.95Nb1.375Mo0.625O5.79 powders consisted of similar to 20 mu m crystals possess orthorhombic Pnma symmetry, whereas the same powders with particle size less 1 mu m have cubic Fd-3m and characterized by decreasing Rb content - Rb0.7Nb1.5Mo0.5O5.58 and Rb0.9Nb1.625Mo0.375O5.62. The crystal structure of Rb0.7Nb1.5Mo0.5O5.58 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 Rb0.95NbxMo2-xO6.475-0.5x (x=1.31-1.663) compounds have been studied. Moreover the comparison of electronic structure for cubic and orthorhombic phases has been performed.

Automated summary

The size induced phase transition of non-cubic beta-pyrochlore compounds Rb0.95NbxMo2-xO6.475-0.5x (x=1.31-1.663) has been studied in detail. It was found that powders with larger particle size exhibited an orthorhombic structure, while powders with smaller particle size exhibited a cubic structure. Crystal structure refinement was performed on the cubic phase, and the reasons for structure reconstruction were discussed. Additionally, the electronic structure and band gap of the compounds were studied, with a comparison between cubic and orthorhombic phases.