SYNTHESIS AND ELECTRICAL-CONDUCTIVITY OF SPINEL COMPOUNDS IN THE MG[TI-2]O-4-CENTER-DOT-MG[MGTI]O-4 SYSTEM

We investigated the structural and physical properties of spinel compounds Mg2-xTi1+xO4 in the Mg[Ti-2]O-4-Mg[MgTi]O-4 system. Polycrystalline samples of Mg2-xTi1+xO4-delta (0 less than or equal to x less than or equal to 1.0) were synthesized by the conventional solid-state reaction method. Powder x-ray-diffraction analysis indicated that the samples with 0.33 less than or equal to x less than or equal to 0.67 were nearly single phase of the cubic magnesium titanate spinel. For all the samples, electrical resistivity (rho) exhibited semiconducting behavior at temperatures below 300 K and the magnitude of rho at 77 K was about 1X10(6) Omega cm. For all the single-phase samples, the activation energies (E(a)) were estimated at E(a) similar to 0.34 eV from the Arrhenius plots in the temperature range from 100 to 300 K and, moreover, the magnetic susceptibility versus temperature curves exhibited Curie-Weiss-type behavior at temperatures below 300 K.