Structural phase transition and charge carrier dynamics in Dy containing La6MoO12 ionic conductor

Abstract

The solution combustion method was adopted to prepare a single-phase La6MoO12 compound by doping 10% Dy in the La site and sintered at 800 °C, 1000 °C, and 1200 °C temperatures. The X-ray diffraction patterns confirmed a phase transition of the samples from the cubic fluorite phase (Fm3‾m) to a complex rhombohedral structure (R3‾m) with increasing sintering temperature. The microstrain and particle size show the opposite behaviour in the case of 800 °C and 1200 °C sintered samples. The FE-SEM and XRD results corroborated the increment of particle size with sintering temperature. Elemental mapping confirmed the uniform distribution of elements in the compositions. Red and blue shifts in optical bandgap were observed with sintering temperature. All samples show a negative temperature coefficient of resistance (NTCR) behaviour. The sample sintered at 1200 °C has the highest ionic conductivity of 1.03×10−4Ω−1cm−1 at 540 °C. The reciprocal temperature dependence of conductivity followed the VTF equation. The dielectric loss tangent indicated that all samples have a single relaxation process. The time-temperature superposition principle has been verified from the scaling of the dielectric loss tangent.