ELECTRONIC TRANSPORT PHENOMENA OF LA2/3+XTIO3-DELTA (X-LESS-THAN-0.2) - METAL-NONMETAL TRANSITION BY ELECTRON DOPING

Carriers were introduced into La2/3TiO3, an insulator with double perovskite structure having an A-site vacancy, by a hydrogen reduction, and their electronic transport phenomena and crystal structure were studied. The lightly doped samples showed semiconducting behavior, while the heavily doped samples showed metallic conductivity. This carrier-concentration-dependent metal-nonmetal transition has been found at 3d electron density of 0.33 per formula unit with simultaneous occurrence of a crystal symmetry change from P4/mmm to Pnma. The electronic state of the La2/3+xTiO3-delta system was characterized by measuring the resistivity, the Seebeck coefficient, and the magnetic susceptibility. (C) 1994 Academic Press, Inc.