Synthesis and ion transport properties of RE3GaO6 (RE = rare earth) oxide ion conductors

Abstract

First-principles calculations were conducted, which proposed that members of the RE3GaO6 (RE = rare earth) system were oxide ion conductors. This study experimentally verified oxide ion conduction in Dy3GaO6, Er3GaO6, and Nd3GaO6. The sintered bodies were synthesized by a solid-state reaction method, and their properties were characterized. The samples with dopants were observed to be mixed electron and oxide ion conductors. Dy2.85Ca0.15GaO6-δ exhibited oxide ion conductivities of 2.1 × 10−4 S/cm at 973 K, with an oxide ion transport number of 21 % under O2 gas flow. Additionally, the Rietveld refinement suggested that oxide ion migration might occur via the oxide ion vacancy between the O2 sites. Overall, the oxide ion conductivities of RE3GaO6 increased in the following order: Nd > Dy > Er, which was in good agreement with that predicted by using the first-principles calculations. The discrepancy between the experimentally measured and predicted conductivities was caused by the solid-solution limit at the RE site for the dopants.