Direct-current conductivity and dielectric relaxation measurements were used to study the effect of La substitution upon dielectric properties and O-ion transportation in PbMoO4 samples. The direct-current conductivity of La-doped samples was about 10-3S/cm around 1073K. A dielectric loss peak with an activation energy of 0.6 to 0.8eV was observed in the temperature spectrum as well as in the frequency spectrum for all La-doped PbMoO4 samples. With increasing La doping content, this peak became higher and shifted to higher temperature or lower frequency, and the activation energy became larger. It was suggested that this dielectric loss peak was associated with the short-distance diffusion of O ions (or O vacancies) between the 16f and 8e sites of the scheelite structure type with I41/a symmetry.

Dielectric Relaxation Study of Pb1-xLaxMoO4+δ (x = 0–0.3) Oxide-Ion Conductors. G.G.Zhang, Q.F.Fang, X.P.Wang, Z.G.Yi: Journal of Physics - Condensed Matter, 2003, 15[24], 4135-42