Physical properties of the perovskite SrTiO3−δ synthetized by chemical route

Abstract

The perovskite SrTiO3−δ elaborated by chemical route was characterised by physical and electrochemical methods. The oxide crystallizes in a cubic structure with a lattice parameter of 3.907(5) Å and a crystallite dimension of 71 nm. The morphology visualized by the SEM-EDX analysis shows spherical grains with a mean size of 0.2 μm, formed by agglomeration of crystallites. The diffuse reflectance gave a gap (Eg) of 3.21 eV, ascribed to the charge transfer O2−: 2p → Ti4+: 3d. The thermal variation of the conductivity (σ) obeys an exponential law {σ = σoexp-0.27 eV/T} assigned to low hopping polarons. The electrochemical characterization was undertaken in Na2SO4 solution (10− 1 M) and the n-type character demonstrated from the capacitance measurement and cyclic voltammetry under UV-irradiation, is due to oxygen deficiency. A flat band potential (Efb) of − 0.31 VSCE was determined with a depletion width extended up to ~ 4 μm, advantageous for the formation of electron / hole (e− / h+) pairs. The electrochemical stability against photocorrosion was also shown from the semi-logarithmic plot (log J–E). As application, the Congo Red a diazo dye (CR) is successfully oxidized under UV light on SrTiO3−δ; an abatement of 63% was reached. According to the scavengers mechanism, hydroxyl •OH is the main specie responsible for the CR oxidation. The discoloration follows a pseudo-first-order kinetic with a half-life of 189 min