The thermodynamic characteristics of point defects and the mechanism of charge transfer in lanthanum cobaltite doped with strontium and nickel

Abstract

The specific conductivity and thermal electromotive force (EMF) coefficient of lanthanum cobaltite doped with strontium and nickel La0.9Sr0.1Co0.9Ni0.1O3−δ were measured over the temperature and pressure ranges 1023–1223 K and 10−6−1 atm. The oxide was found to exhibit metallic-type conductivity (800 Ω−1 cm−1 ≤ σ ≤ 1150 Ω−1 cm−1) and small positive thermal EMF coefficient values. A joint analysis of the thermodynamic characteristics of formation of point defects and external T and pO2 parameter dependences of conductivity and thermal EMF showed that charge was transferred in the oxide by small-radius polarons according to the hopping mechanism. The role of polarons was played by electrons MeCo′ and holes MeCo• localized on 3d transition metals. The isothermal dependences of the concentrations and mobilities of charge carriers on the degree of oxygen nonstoichiometry of the oxide studied were calculated.