SYNTHESIS, STRUCTURAL CHARACTERIZATION, AND ELECTRONIC-PROPERTIES OF THE LANI1-XWXO3 ESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-0.25) PEROVSKITE-LIKE SYSTEM

The structural characterization and electronic properties for the LaNi 1-xWxO3 perovskite-like system are reported, Neutron and X-ray powder diffraction data suggest that for the x > 0 phases, an orthorhombic sy mmetry (space group Pbnm) is adopted showing that Ni and W atoms are p laced at random, The evolution of the cell-parameters is in agreement with the different size of the concerned cations in each case, The ele ctronic measurements between 5 and 950 K show a temperature dependence of conductivity very sensitive to the composition, For the 0 less tha n or equal to x less than or equal to 0.20 compounds, a conductivity v ariation very close to metallic behavior is observed whereas the mixed oxide with x = 0.25 behaves as a semiconductor. Both conductivity dat a and Seebeck coefficient measurements are interpreted on the basis of a correlated system in which a metal to insulator transition takes pl ace as a function of temperature and composition, An schematic band mo del consistent with both the electronic properties and structural feat ures is proposed. (C) 1996 Academic Press, Inc.