Structural and electrical properties of Er doped La2Mo2O9 oxide ion conductors

We have studied structure and ionic conductivity of La2-xErxMo2O9 (0.05 <= x <= 0.25). The phase transition observed in La2Mo2O9 is suppressed in Er substituted samples. Cubic beta phase in these samples is confirmed from Rietveld refinement at room temperature. The densification of the samples and grain-grain connectivity are confirmed from scanning electron microscopic study. The X-ray photoelectron microscopic analysis confirms the presence of La, Er, Mo, and O in these samples. The different vibration modes of MoO4 tetrahedral units are confirmed from Fourier transform infrared spectroscopy. The full-widths at half-maximum of all the major absorption bands show high composition dependence. The impedance spectroscopic study is presented in wide temperature and frequency ranges. The temperature dependence of the ionic conductivity is differentiated into three regimes. The effect of grain, grain boundary and electrode polarization on the conductivity is analyzed. The frequency dependence of the conductivity is analyzed using the random free-energy barrier model. The charge carrier relaxation time and its activation energy have been determined from the analysis of the conductivity spectra using the model. (C) 2016 AIP Publishing LLC.