Suppression of magnetism and Seebeck effect in Na0.875CoO2 induced by SbCo dopants

• Main Authors: M. H. N. Assadi, Paolo Mele, Marco Fronzi
• Format: Article
• Language: English
• Published: SpringerOpen 2020-01-01
• Series: Materials for Renewable and Sustainable Energy
• Subjects: Sodium cobaltate; Sb dopant; Thermoelectric effect; Magnetism; Density functional theory
• Online Access: https://doi.org/10.1007/s40243-020-0165-9

Abstract We examined the electronic property of Sb-doped Na0.785CoO2 using density functional calculations based on GGA+U formalism. We demonstrated that Sb dopants were the most stable when replacing Co ions within the complex Na0.875CoO2 lattice structure. We also showed that the SbCo dopants adopted the + 5 oxidation state introducing two electrons into the host Na0.875CoO2 compound. The newly introduced electrons recombined with holes that were borne on Co4+ sites that had been created by sodium vacancies. The elimination of Co4+ species, in turn, rendered Na0.875(Co0.9375Sb0.0625)O2 non-magnetic and diminished the compound’s thermoelectric effect. Furthermore, the SbCo dopants tended to aggregate with the Na vacancies keeping a minimum distance. The conclusions drawn here can be generalised to other highly oxidised dopants in Na x CoO2 that replace a Co.