Effect of high oxygen deficiency in nano-confined bismuth sesquioxide. (29th April 2020)

• Record Type: Journal Article
• Authors: Sanna, Simone; Firodaliso, Elisabetta Maria; Kasama, Takeshi; Castelli, Ivano E; Esposito, Vincenzo
• Is Part Of: JPhys energy. Volume 2:Number 2(2020)
• Publication Date: 2020-04-29
• Subjects: Bi2O3 -- YSZ -- heterostructure -- thin films -- nanoionics; Power resources -- Research -- Periodicals; Power resources -- Periodicals; 333.79
• DOI: 10.1088/2515-7655/ab783a
• Languages: English
• ISSNs: 2515-7655

Abstract

Abstract: Bismuth sesquioxide in its cubic form, i.e. δ -Bi2 O3, is the fastest oxygen ionic conductor known which has important applications in energy technologies. However, the material is unstable as it undergoes high-density polymorphic transitions and degradation. In this work, we show that δ -Bi2 O3 can be stabilized both at high and low temperatures (T < 775 °C) under low oxygen partial pressure (pO2 < 10 −5 atm), where the material is nanostructured in multilayered thin film coherent heterostructures with yttrium stabilized zirconia. Density Functional Theory calculation confirms such a form of metastability, also showing that high oxygen defect concentration favors the cubic phase. Moreover, high oxygen deficiency in the nanoionics leads to an unexpected 'two-regime' conductivity with high values ( σ > 1 S cm −1 at 600 °C) at high pO2 and lower ionic conductivity ( σ ∼ 0.1 S cm −1 at 600 °C) at low pO2 . Ionic conductivity at low pO2 occurs with high activation energy (Ea > 1.5 eV), suggesting a drastic decrease in mobility for high concentration of defects.