Dielectric relaxation studies of Ba-doping effects on the oxygen-ion diffusion and phase transition in La2Mo2−yWyO9 ceramics

The influence of barium doping on the oxygen-ion diffusion and phase transition in the La2Mo2−yWyO9 (y=0, 1) oxide-ion conductors has been investigated via dielectric measurements. In the Ba-doped La2Mo2O9 samples there are only two dielectric relaxation peaks Pd1 and Pd2, which are associated with the short-distance diffusion of oxygen vacancies. But in the Ba-doped La2MoWO9 samples, three peaks are detected, including peaks Pd1, Pd2, and Ph. The last is associated with the phase transition process from the static disordered state to the dynamic disordered state of oxygen ion/vacancy distribution. With the increasing amount of Ba2+ in La2MoWO9 sample, the Ph peak shifts to higher temperature, while the height and width of Ph peak increase. Based on the ionic radius and substitution sites of Ba2+ and W6+ the substitution effects on the phase transition corresponding to peak Ph were discussed.