A new defect chemistry model for Nb-doped SrCoO2.5+delta: The role of oxygen interstitials and delocalized-to-localized electron holes

作者：Wang Jie; Jin Xinfang; Huang Kevin^*

来源：Journal of Solid State Chemistry, 2017, 246: 97-106.

DOI：10.1016/j.jssc.2016.11.008

• Defect chemistry
• Oxygen interstitials
• Delocalized and localized holes
• Oxygen stoichiometry
• Hole mobility

A new defect chemistry model featuring oxygen interstitials (O-I('')) and delocalized-to-localized d-electron holes (Co-Co) as point defects is demonstrated under a perfect Brownmillerite SrCoO2.5 reference framework to elucidate transport properties of Nb-doped SrCoO2.5+delta (SCN) system over a range of partial pressure of oxygen (Po-2) and temperature (T). With this new defect chemistry model, the electronic conductivity behaviors with T and Po-2 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-Po-2 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.

• 出版日期2017-2