Investigation of ion transport properties in Er–W co-doped La2Mo2O9 electrolytes

Abstract

Here we present the structural, vibrational, dielectric as well as ionic transport properties in a series of La2-xErxMo1.7W0·3O9 (for 0 ≤ x ≤ 0.5). Stabilization of cubic β-phase at room temperature was achieved by doping, evident from XRD and conductivity plots. Raman analysis suggests a change in phase structure and deformation in Mo-polyhedra due to doping. Ionic conductivity of 10 mol% Er-doped sample was found to be 3.6 × 10−2 S/cm similar to that of pure La2Mo2O9 at 700 °C. Two different conduction mechanisms prevail: Arrhenius type below 450 °C and Vogel-Tammann-Fulcher (VTF) type above 450 °C. Dielectric constant and loss studies indicate the presence of two dielectric relaxations in the co-doped samples with different relaxation times attributed to the short-range diffusion of oxygen ions between different sites, i.e., O (1) ↔ O (2) and O (1) ↔ O (3). Electric modulus studies suggests that the relaxation mechanism is independent of temperature and composition.