The effects of configuration-entropy and aliovalent-doping on the electrical and stability properties of bixbyite oxides

Abstract

The bixbyites Ln₂O₃ materials which have the defect fluorite structure show limited ionic conduction and poor chemical stabilities. To find solutions to overcome these drawbacks, herein the effect of configuration entropy and aliovalent-doping (Ca-, Mg-, Ba-, and Zr-doping) for Ln on the electrical properties and stabilities of Ln₂O₃ were thoroughly investigated. The results disclosed that Ca- Mg- or Ba-doping could considerably improve the samples’ electrical conductivities as expected, with the Ca-doping leading to dominating ionic conduction, while both Mg- and Ba-doping resulted in dominating electronic conduction. For the Zr-doping, the electrical conductivities increased with doping level, with the samples 0 ≤ x ≤ 0.5 dominated by electronic conduction while the samples 0.6 ≤ x ≤ 0.8 showing dominating ionic conduction. For stability properties, enhancing the configuration entropy would increase the chemical stabilities of the Ln₂O₃-based materials. Therefore, Ca- and Zr-doping are beneficial to improving both the stabilities and ionic conductivities.