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

Abstract

We examined the electronic property of Sb-doped Na 0.785 CoO 2 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 Na 0.875 CoO 2 lattice structure. We also showed that the Sb Co dopants adopted the + 5 oxidation state introducing two electrons into the host Na 0.875 CoO 2 compound. The newly introduced electrons recombined with holes that were borne on Co 4+ sites that had been created by sodium vacancies. The elimination of Co 4+ species, in turn, rendered Na 0.875 (Co 0.9375 Sb 0.0625)O 2 nonmagnetic and diminished the compound's thermoelectric effect. Furthermore, the Sb Co 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 CoO 2 that replace a Co.

Review of the thermoelectric properties of layered oxides and chalcogenides

“…The presence of magnetic atoms in oxide thermoelectrics increases their thermoelectric characteristics by increasing the thermoelectric power [30,31]. The presence of a magnetic field also changes the thermoelectric properties of oxide thermoelectrics [32][33][34].…”