Nb-Doped La[sub 2]Mo[sub 2]O[sub 9]: A New Material with High Ionic Conductivity

A new series of -based oxides of the general formula , where , was prepared by a citrate-nitrate combustion process, and the electrical and thermal properties were evaluated. Electrical conductivity measurements on the sintered samples confirmed that all the compositions underwent a phase transition below with a concomitant increase in the oxide-ion conductivity. Although Nb doping did not suppress the order-disorder transition exhibited by pure completely, it has significantly lowered both the transition temperature and the enthalpy change associated with the transition. The oxide-ion conductivity was found to decrease with increasing Nb concentration, and at , compositions with values of 0.06 and 0.1 exhibited oxide-ion conductivities of 0.069 and , respectively. The composition with the lowest Nb doping, viz., , exhibited an oxide-ion conductivity of at , which is nearly double that of the undoped material, and this is the highest value reported so far in this family of oxides.