The effects of W-doping were studied in La2Mo2-xWxO9 samples (x = 0, 0.1, 0.25, 0.5, 0.75, 1.0, 1.2, 1.4) by using dielectric relaxation measurements. In addition to the low-temperature relaxation peak, Pd, which was associated with O-ion diffusion, a new dielectric loss peak, Ph, was observed at about 740K. With increasing W concentration, the activation energy of the Pd peak increased and saturated at a value of about 1.45eV. The height of the Ph peak first increased, and then decreased, after passing through a maximum at 25%W. With increasing measurement frequency, the height of the Ph peak decreased monotonically but its position shifted very little. The Ph peak in pure and W-doped La2Mo2O9 was suggested to be associated with a phase transition from the static disordered state to the dynamic disordered state in the O ion/vacancy distribution.

Phase Transition Associated with the Variation of Oxygen Vacancy/Ion Distribution in the Oxide-Ion Conductor La2Mo2-xWxO9. D.Li, X.P.Wang, Q.F.Fang, J.X.Wang, C.Li, Z.Zhuang: Physica Status Solidi A, 2007, 204[7], 2270-8