Investigation of the localized oxide ion interstitials of PbWO4-based oxide ion conductors by means of impedance spectroscopy

Abstract Impedance spectra were measured for two types of lanthanum-substituted PbWO 4 systems (Pb 1 −  x La 2 x /3 WO 4 and Pb 1 −  x La x WO 4 +  x /2 ), from which the relaxation phenomena associated with oxide ion conduction were investigated. Profiles of the imaginary part of the electric modulus normalized at the peak position were not essentially varied with temperature or composition for Pb 1 −  x La 2 x /3 WO 4 system, whereas broadening of the modulus peak was observed for Pb 1 −  x La x WO 4 +  x /2 system. We attributed this broadening to the localization of oxide ion interstitials since it appeared only for the latter system and the peak broadening grew larger with decreasing temperature.