Conduction and relaxation mechanisms in bismuth doped La2Mo2O9 ionic conductors

Oxygen ion conduction and relaxation mechanisms in bismuth substituted La2Mo2O9 have been reported in this paper. The phase transition observed in La2Mo2O9 is suppressed in bismuth substituted samples, and the cubic beta form is stabilized at room temperature. A transition of the dc anionic conductivity from low temperature Arrhenius type to high temperature Arrhenius type has been observed in La2Mo2O9. However, for bismuth doped samples the dc anionic conductivity shows a transition from Arrhenius behavior at low temperatures to Vogel-Tamman-Fulcher in the high temperature regime. The frequency dependence of the ac conductivity shows a power law behavior. The ac conductivity remains constant in low frequency region but shows dispersion at the crossover frequency. The crossover frequency shifted towards higher value with the increase of temperature. The dimensionality of the conduction space does not change with bismuth doping. The scaling behavior of the conductivity spectra for different temperatures and compositions indicates that dynamics of oxygen ions is independent of temperatures and compositions. (C) 2013 AIP Publishing LLC.