Formation of protonic defects in perovskite-type oxides with redox-active acceptors: case study on Fe-doped SrTiO3

Abstract

The thermodynamics of water incorporation into Fe-doped SrTiO₃ was investigated by thermogravimetric measurements. Changes in valence states of redox-active dopant ions (Fe³⁺/Fe⁴⁺) with water vapor pressure were taken into account in the defect chemical analysis. The proton solubility was significantly enhanced by the presence of the redox centers. The hydration enthalpies and entropies were −60 kJ mol⁻¹ and −122 J mol⁻¹ K⁻¹. The defect chemical model was applied to describe the water vapor dependence of the electrical conductivity in mixed ionic and electronic conducting Fe-doped SrTiO₃ single crystals.