Defects and dopant properties of SrSnO3 compound: A computational study

Abstract

Strontium stannate, with the general formula SrSnO3, is a promising photocatalyst. However, it has some limitations: for example, its gap is too large for the efficient conversion of solar energy to photocatalytic activity. In order to optimise SrSnO3 for the activity of visible light, several dopants such as rare earths, transition metals and others are investigated using atomistic simulation. The main issues related to intrinsic defects, dopant incorporation and reduction properties in SrSnO3 are examined. Our simulation model gives a good reproduction of the MSnO3 structure. The most favourable intrinsic defect is the antisite defect. Particular attention is given to the electronic processes of oxidation and reduction, due to their importance in relation to the practical applications of the material. For divalent and tetravalent dopants, the mechanisms with the lowest solution energy are isovalent, while for trivalent dopants, there was a preference related to the nature (rare earth, transition metal) of the dopant in SrSnO3. The trivalent transition metal dopants were preferentially incorporated at Sn4+ sites with oxygen vacancy compensation in SrSnO3. The rare earth group in SrSnO3 is energetically more favourable for incorporation in the Sr2+ site compensated by strontium antisite defects. The results indicate that the pentavalent dopants at Sn4+ sites are the most soluble in SrSnO3. Pentavalent dopants preferred the Sn site. The R–O distances and R-O-Sn angle were also investigated, and the R–O distance was found to decrease when Sr2+ and Sn4+ ion sites were doped with most of the dopant ions. For R-O-Sn, the angle increases when doping at the Sn4+ site with rare earth ions and increases for the rest of the dopants used in this work. For Sr2+ doping, all dopants used in this work decreased the R-O-Sn angle.