Optimizing rhombohedral Bi2O3 conductivity for low temperature SOFC electrolytes

Room-Temperature Oxygen Transport in Nanothin BixOySez Enables Precision Modulation of 2D Materials

“…Figure b shows the R m Bi 2 O 3 phase. Although previous work reported bulk rhombohedral Bi 2 O 3 , it required dopants to stabilize it, or its existence in a solid solution (see Section S1 in the Supporting Information for additional information). − , Our work suggests that R m Bi 2 O 3 is stable under ambient conditions as a nanothin film. Figure c–f illustrates Bi x O y Se z facilitating the transport of oxygen into the interlayer region, thereby modifying the 2D material environment and its coupling to Bi x O y Se z .…”

“…This is a surprising identification, since, to the best of our knowledge, pure bulk R m Bi 2 O 3 has not been demonstrated, and inspection of the phonon modes reveals imaginary modes, suggesting that pure R m Bi 2 O 3 is not stable at 0 K (Section S4 in the Supporting Information). However, bulk rhombohedral Bi 2 O 3 stabilized by lanthanide dopants or in solid solution with lanthanide oxides has been demonstrated at noncryogenic tempertatures. − , Further work is required to elucidate whether Se point defects influence the stability and to determine the effect of various concentrations of selenium. Taken together, our work and literature on rhombohedral Bi 2 O 3 suggest that a combination of structural, chemical, and environmental factors stabilize the rare Bi 2 O 3 phase in our experiments.…”

“…However, bulk rhombohedral Bi 2 O 3 stabilized by lanthanide dopants or in solid solution with lanthanide oxides has been demonstrated at noncryogenic tempertatures. [9][10][11]15 Further work is required to elucidate whether Se point defects influence the stability and to determine the effect of various concentrations of selenium.…”

“…Bismuth oxide based materials are leading candidates for advanced SOFCs − and oxygen separation membranes, having demonstrated exceptional oxygen transport properties. Bismuth oxide exhibits polymorphism, where the properties can vary dramatically across different phases (i.e., crystal structures) .…”

Morphology and Structural Stability of Bismuth-Gadolinium Co-Doped Ceria Electrolyte Nanopowders

“…Among the many possible SOFC electrolytes reported in the literature, bismuth oxide with a fluorite-like structure (δ-Bi 2 O 3 ) exhibits the highest oxygen ionic conductivity [1,20] due to the combination of a high concentration of oxygen vacancies (around 25%) and greater anion mobility [21]. Nevertheless, the use of pure δ-Bi 2 O 3 is limited to a very narrow temperature range: 730-824 • C. In fact, pure δ-Bi 2 O 3 melts above 824 • C and, upon cooling below 730 • C, the transition from the δ-cubic phase to either the metastable tetragonal β-phase, the body-centered cubic (BCC) γ-phase, or the monoclinic α-phase [22], takes place, thus resulting in a discontinuous drop in ionic conduction and in an unfavorable increase of the electronic conductivity [23,24]. To stabilize the δ-Bi 2 O 3 phase, the doping with another oxide in tetravalent (CeO 2 ) or trivalent systems (CeO 2 -Gd 2 O 3 ) with appropriate compositions is strictly necessary.…”