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<p>This paper is to investigate the stability of cubic δ-phase with high ionic conductivity in doped Bi<sub>2</sub>O<sub>3</sub> systems and its effect on electrical conductivity. Yb<sub>2</sub>O<sub>3</sub> doped Bi<sub>2</sub>O<sub>3</sub> solid electrolyte material was synthesized by solid-state reaction method under atmospheric conditions. XRD analysis confirmed that single-phase cubic δ-Bi<sub>2</sub>O<sub>3</sub> was stabilized in samples containing ≥ 15&#xa0;mol% Yb<sub>2</sub>O<sub>3</sub> (A3–A5), while mixed <i>β</i> and <i>δ</i> phases were observed in lower doped samples (A1, A2). Although there are clusters in the EDAX images of sample A1 and A2, the highest ionic conductivity was measured as 0.0294 S/cm at 750&#xa0;°C in sample A2. The average crystallite size decreased from 52&#xa0;nm (A1) to 25&#xa0;nm (A2) and there was a corresponding increase in microstrain from 1.887 × 10⁻<sup>3</sup> to 3.658 × 10⁻<sup>3</sup>. The activation energy values ​​ranged from 0.608 to 1.091&#xa0;eV, while A2 exhibited a favorable 0.971&#xa0;eV. The estimated lattice constants confirmed the lattice shrinkage and revealed that partial cation exchange between the host Bi<sup>3</sup>⁺ ions and rare earth elements was successfully achieved. The endothermic peaks observed in the DTA curves at 730&#xa0;°C and 780&#xa0;°C indicate a phase transition and an order–disorder transition occurred in the anion sublattice of the doped crystal at 600&#xa0;°C. FE-SEM images showed that the grain size was irregular and decreased with increasing Yb<sub>2</sub>O<sub>3</sub> content. In Yb-rich compositions, the surface porosity increases, which leads to decreased conductivity upon doping. These findings indicate that controlled Yb<sub>2</sub>O<sub>3</sub> doping can significantly stabilize the δ-phase and enhance the ionic transport properties in Bi₂O₃-based SOFC electrolytes. It also provides a new perspective on the relationships between lattice strain and conductivity.</p>

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Synthesis and characterization of Yb2O3-doped Bi2O3 solid electrolyte composite material

  • 期刊论文

  • 发表日期：

    2025年7月29日

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  • Zeliha Atioğlu

摘要

This paper is to investigate the stability of cubic δ-phase with high ionic conductivity in doped Bi2O3 systems and its effect on electrical conductivity. Yb2O3 doped Bi2O3 solid electrolyte material was synthesized by solid-state reaction method under atmospheric conditions. XRD analysis confirmed that single-phase cubic δ-Bi2O3 was stabilized in samples containing ≥ 15 mol% Yb2O3 (A3–A5), while mixed β and δ phases were observed in lower doped samples (A1, A2). Although there are clusters in the EDAX images of sample A1 and A2, the highest ionic conductivity was measured as 0.0294 S/cm at 750 °C in sample A2. The average crystallite size decreased from 52 nm (A1) to 25 nm (A2) and there was a corresponding increase in microstrain from 1.887 × 10⁻3 to 3.658 × 10⁻3. The activation energy values ​​ranged from 0.608 to 1.091 eV, while A2 exhibited a favorable 0.971 eV. The estimated lattice constants confirmed the lattice shrinkage and revealed that partial cation exchange between the host Bi3⁺ ions and rare earth elements was successfully achieved. The endothermic peaks observed in the DTA curves at 730 °C and 780 °C indicate a phase transition and an order–disorder transition occurred in the anion sublattice of the doped crystal at 600 °C. FE-SEM images showed that the grain size was irregular and decreased with increasing Yb2O3 content. In Yb-rich compositions, the surface porosity increases, which leads to decreased conductivity upon doping. These findings indicate that controlled Yb2O3 doping can significantly stabilize the δ-phase and enhance the ionic transport properties in Bi₂O₃-based SOFC electrolytes. It also provides a new perspective on the relationships between lattice strain and conductivity.