Physical characterization of the semiconducting deficient perovskite BaSnO3-δ

The semiconducting stannate BaSnO3-delta, prepared in evacuated silica ampoule, crystallizes in a cubic perovskite structure. The magnetic susceptibility (less than 2 x 10(-5) emu cgs mol(-1)) is due to itinerant electrons. The conductivity obeys to an exponential law sigma(0) exp (-E-a/kT) with activation energy of 3 meV and electrons hopping between mixed valences Sn2+/4+. A variable range hopping is predicted from the non linear behavior of the plot In (sigma) versus T-1. At high temperatures, the conductivity follows a thermally activated hopping of lattice polaron with activation energy of 0.17 eV. The plot deviates from the linear behavior due to the oxidation of BaSnO3-delta; the fully oxidized specimen is restored at 578 K in air. The thermal variation of the thermopower suggests a finite density of states at the Fermi level. The semiconducting properties are elucidated from the photo-electrochemical characterization. The Mott-Schottky plot in alkaline medium shows a straight line from which an electron density of 3.07 x 10(21) cm(-3), a flat band potential of -0.375 V-SCE and a space charge region of 2.3 A have been determined. (C) 2014 Published by Elsevier Ltd.