First-Principles Selection of Solute Elements for Er-Stabilized Bi2O3 Oxide-Ion Conductor with Improved Long-Term Stability at Moderate Temperatures

• Published in: Chemistry of materials 2017-04, Vol.29 (8), p.3763-3768
• Main Authors: Shitara, Kazuki, Moriasa, Takafumi, Sumitani, Akifumi, Seko, Atsuto, Hayashi, Hiroyuki, Koyama, Yukinori, Huang, Rong, Han, Donglin, Moriwake, Hiroki, Tanaka, Isao
• Format: Article
• Language: English
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/acs.chemmater.7b00846

Quality oxide-ion conductors are essential for clean-energy applications. Rare-earth-stabilized bismuth sesquioxide, δ-Bi2O3, exhibits a much greater oxide-ion conductivity at high temperatures than commonly used ZrO2- or CeO2-based electrolytes, but it suffers from serious conductivity degradation while annealing at moderate temperatures of ∼773 K, which is the target temperature for many applications. Here, we demonstrate that a novel set of solute elements for δ-Bi2O3 can significantly enhance the long-term stability at 773 K. A pure oxide-ion conductivity of 0.035 S/cm at 773 K remains unchanged during annealing for 100 h, which is five times greater than the best known solid-state oxide materials after long-term annealing. For materials design, we explore a range of chemical spaces using theoretical methods based on first-principles calculations. The order–disorder transition temperature of the anion sublattice, oxygen-ion diffusivity, and solution free energy are used as descriptors. The design concept is verified experimentally.