A new defect chemistry model for Nb-doped SrCoO_2.5+δ: The role of oxygen interstitials and delocalized-to-localized electron holes

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• 作者：Jie Wang ; Xinfang Jin ; Kevin Huang ; ^{huang46@cec.sc.edu}
• 关键词：Defect chemistry ; Oxygen interstitials ; Delocalized and localized holes ; Oxygen stoichiometry ; Hole mobility
• 刊名：Journal of Solid State Chemistry
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：246
• 期：Complete
• 页码：97-106
• 全文大小：1523 K
• 卷排序：246

文摘

A new defect chemistry model featuring oxygen interstitials (OI") and delocalized-to-localized d-electron holes (CoCo·) as point defects is demonstrated under a perfect Brownmillerite SrCoO2.5 reference framework to elucidate transport properties of Nb-doped SrCoO2.5+δ (SCN) system over a range of partial pressure of oxygen (Po2) and temperature (T). With this new defect chemistry model, the electronic conductivity behaviors with T and Po2 can be well interpreted by the change in concentration of d-electron holes migrating with a constant mobility. The important concentration contours of electron holes, excess electrons and oxygen interstitials are mapped out on the T-Po2 domain, from which hole-concentration and conductivity under iso-stoichiometry are reconstructed. The partial/integral molar thermodynamic properties and thermodynamic factor of the SCN solid solution are also determined. A transitional delocalized-to-localized hole-transport mechanism with decreasing oxygen stoichiometry is discussed based on p=p(T) obtained under constant oxygen stoichiometry.