Electrical conduction in (La0.97Sr0.03)2(Mo1 − xGax)2O9 − α ceramics

A novel series of ceramic samples (La0.97Sr0.03)2(Mo1 − xGax)2O9 − α (x = 0, 0.01, 0.03, 0.05, 0.08) were prepared by a solid-state reaction method. All the doubly doped ceramics have a single cubic structure except (La0.97Sr0.03)2(Mo0.92Ga0.08)2O9 − α. The conduction behaviors of the samples with x ≤ 0.05 were investigated using various electrochemical methods including gas concentration cells, oxygen electrochemical permeation and AC impedance spectroscopy in the temperature range of 823–1273 K. In dry oxygen-containing atmosphere, the ceramic samples were almost pure oxide-ionic conductors. In wet oxygen-containing atmosphere, the ceramic samples were also almost pure oxide-ionic conductors, but didn't possess the protonic conduction. The electrochemical oxygen permeation experiment further verified the oxide-ionic conduction nature under oxygen-containing atmosphere. The phase transition has been completely suppressed in the doubly doped samples in both dry and wet air atmospheres. The oxide-ionic conductivities were affected by the doping levels, and increased in the order: σ (x = 0.05) < σ (x = 0) < σ (x = 0.03) < σ (x = 0.01). (La0.97Sr0.03)2(Mo0.99Ga0.01)2O9 − α exhibited the highest oxide-ionic conductivity of 0.103 S cm−1 at 1273 K.

Research highlights
► A novel series of (La0.97Sr0.03)2(Mo1 − xGax)2O9 − α were prepared.
► The solubility limit of Ga in (La0.97Sr0.03)2(Mo1 − xGax)2O9 − α was at least x = 0.05.
► The samples were almost pure oxide-ionic conductors in oxygen-containing atmospheres.
► The phase transition has been completely suppressed in the doubly doped samples.
► The conductivities increased in the order: σ(x = 0.05) < σ(x = 0) < σ(x = 0.03) < σ(x = 0.01).