Metal-semiconductor transition in non-stoichiometric double perovskite Sr2FexMo2-xO6

The electronic transport properties of the ordered double perovskite oxides Sr2FexMo2-xO6 (0.8≤x≤1.5) have been investigated. In this system, the samples (x≥1.2) are semiconducting in the temperature range of 4.2≤T≤300 K. A metal-semiconductor transition occurs when x<1.2 and the transition temperature TMS decreases obviously as the Fe content decreases. Rietveld refinement of the X-ray powder diffraction profiles indicates that the crystal structure of the compounds Sr2FexMo2-xO6 changes from a tetragonal I4/mmm lattice to a cubic Fm3-barm lattice around x=1.2