METAL-INSULATOR TRANSITIONS INDUCED BY DOPING IN LANIO3 - LANI0.95MO0.05O3 (M = MO, W, SB, TI, CU, ZN) PEROVSKITES

Structural characterization and electronic properties of the LaNi0.95M 0.05O3 (M = Mo, W, Sb, Ti, Cu, Zn) perovskite-like system are reported . These compounds can be regarded as being derived from LaNiO3 by part ial substitution of Ni3+ in this material by M6+, M5+, M4+, or M2+ for mal cations, with a partial reduction of Ni3+ to Ni2+ taking place. X- ray powder diffraction data were analyzed by means of the Rietveld met hod and show that all the title materials present perovskite-type stru cture with a rhombohedral (S.G. R (3) over bar c) or orthorhombic (S.G . Pbnm) symmetry, depending on the nature of the M cation. In all case s, Ni and M cations are placed at random in octahedral B-sites of pero vskite structure. Electrical resistivity measurements (four probe meth od) show metal-to-insulator (M-I) transitions for M = Mo, W, Ti, Cu, Z n at temperatures of about 50 K and a semiconductor behavior for the S b sample in the whole temperature range explored. Magnetic susceptibil ity measurements show the presence of weak ferromagnetic interactions for M = Sb and Pauli paramagnetism for the remaining compounds. (C) 19 98 Academic Press.