Spallation Neutron Source , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37830 , United States.
Department of Chemistry , University of Calgary , Calgary , Alberta T2N 1N4 , Canada.
Inorg Chem. 2018 May 7;57(9):5607-5614. doi: 10.1021/acs.inorgchem.8b00571. Epub 2018 Apr 17.
Solid oxide fuel cells (SOFCs) are solid-state electrochemical devices that directly convert chemical energy of fuels into electricity with high efficiency. Because of their fuel flexibility, low emissions, high conversion efficiency, no moving parts, and quiet operation, they are considered as a promising energy conversion technology for low carbon future needs. Solid-state oxide and proton conducting electrolytes play a crucial role in improving the performance and market acceptability of SOFCs. Defect fluorite phases are some of the most promising fast oxide ion conductors for use as electrolytes in SOFCs. We report the synthesis, structure, phase diagram, and high-temperature reactivity of the ScV O (0 ≤ x ≤ 2.00) oxide defect model system. For all ScV O phases with x ≤ 1.08 phase-pure bixbyite-type structures are found, whereas for x ≥ 1.68 phase-pure corundum structures are reported, with a miscibility gap found for 1.08 < x < 1.68. Structural details obtained from the simultaneous Rietveld refinements using powder neutron and X-ray diffraction data are reported for the bixbyite phases, demonstrating a slight V preference toward the 8b site. In situ X-ray diffraction experiments were used to explore the oxidation of the ScV O phases. In all cases ScVO was found as a final product, accompanied by ScO for x < 1.0 and VO when x > 1.0; however, the oxidative pathway varied greatly throughout the series. Comments are made on different synthesis strategies, including the effect on crystallinity, reaction times, rate-limiting steps, and reaction pathways. This work provides insight into the mechanisms of solid-state reactions and strategic guidelines for targeted materials synthesis.
固体氧化物燃料电池（SOFC）是一种固态电化学装置，可将燃料的化学能高效地直接转化为电能。由于其燃料灵活性、低排放、高转换效率、无运动部件和安静运行等特点，被认为是满足未来低碳需求的有前途的能源转换技术。固体氧化物和质子导体电解质在提高 SOFC 的性能和市场接受度方面发挥着关键作用。缺陷萤石相是一些最有前途的快速氧离子导体，可用作 SOFC 的电解质。我们报告了 ScV O（0 ≤ x ≤ 2.00）氧化物缺陷模型系统的合成、结构、相图和高温反应性。对于所有 x ≤ 1.08 的 ScV O 相，均发现单相的钙钛矿型结构，而对于 x ≥ 1.68 的相，则报道了单相的刚玉型结构，在 1.08 < x < 1.68 范围内发现了混溶性间隙。使用粉末中子和 X 射线衍射数据进行的同时 Rietveld 精修获得的结构细节报告了钙钛矿相，表明 V 略微优先占据 8b 位。原位 X 射线衍射实验用于研究 ScV O 相的氧化。在所有情况下，均发现 ScVO 是最终产物，x < 1.0 时伴有 ScO，x > 1.0 时伴有 VO；然而，整个系列的氧化途径差异很大。对不同的合成策略进行了评论，包括对结晶度、反应时间、速率限制步骤和反应途径的影响。这项工作为深入了解固态反应机制和有针对性的材料合成战略提供了参考。
