Studies on some titanium-substituted Fe2MoO4 spinel oxides

Electrical resistivity (rho) and thermoelectric power (alpha) measurements were carried out in inert atmosphere on Fe2Mo1-x TixO4 (0.0 less than or equal to x less than or equal to 1.0) spinel oxides in the temperature ranges 100-600 and 30-600 K, respectively. Thermal activation energy (E-a), carrier concentration (n), activation energy for carrier concentration generation (E-n), and mobility (mu) values have been calculated from resistivity and thermoelectric power data. The results show that conduction in titanium-substituted Fe2MoO4 samples, i.e., Fe2Mo1-xTixO4, is carried out through the hopping of charge carriers, and the linear In (rho) vs 1/T plots show a break at the magnetic phase transition temperature. Progressive substitution of molybdenum by titanium in Fe2MoO4 shows that the ratio of Fe3+/Fe2+ decreases and in Fe2TiO4 the ratio is very small. The decrease in the amount of Fe3+ with increasing x results in the high resistivity and large lattice parameter of Fe2TiO4. (C) 1998 Academic Press.