Thermomigration kinetics and a novel method to determine the chemical diffusivity of a mixed conductor

The kinetics of temperature-gradient-induced nonstoichiometry redistribution or δ-thermomigration of a mixed ionic electronic conductor, e.g., ABOν + δ has been solved analytically in closed form over the entire time span for the first time ever and hence, the temporal behaviors of the measurable, ionic and electronic thermovoltages. The latter allow one to determine the chemical diffusivity of the mobile component, say, O, in addition to the entropic quantities governing the thermomigration, under a temperature gradient more simply and easily compared to the conventional relaxation method under an oxygen potential gradient. The validity and workability of the novel method has been demonstrated by measuring the chemical diffusivity on the system of BaCo0.70Fe0.22Nb0.08O3 − δ and comparing with those as measured conventionally. The advantage of the novel method is discussed in comparison with the conventional relaxation method.