Effect of alkaline-doping on the properties of La2Mo2O9 fast oxygen ion conductor

Synthesis by means of a modified Pechini method of pure and alkaline-doped (Na, K and Rb) La2Mo2O9 (LAMOX) is presented. The electrical conductivity of LAMOX prepared by this method is completely analogous to that of the solid state prepared material. Doping with K and Rb hinders the alpha --> beta phase transition found in the pure and Na-doped material around 580degreesC. Electrical measurements as a function of pO(2) shows that LAMOX has a mainly ionic conductivity down to 10(-18) atm. The electrical conductivity of the doped samples is close to that of the pure molybdate for temperatures higher than about 600degreesC, while for K- and Rb-doped samples the conductivity is higher for lower temperatures, as a consequence of the absence of the phase transition. Finally, a non-Arrhenius behaviour is observed for all the investigated samples and correlated, at a first approximation, to the structural peculiarities of the LAMOX family.