Effect of Oxygen Nonstoichiometry on Electrical Conductivity and Thermopower of Gd_0.2Sr_0.8FeO_3-δ Ferrite Samples

The behavior of the resistivity and thermopower of the Gd_0.2Sr_0.8FeO_3-δ ferrite samples with a perovskite structure and the sample stability in an inert gas atmosphere in the temperature range of 300⁻800 K have been examined. It has been established that, in the investigated temperature range, the thermoelectric properties in the heating‒cooling mode are stabilized at δ ≥ 0.21. It is shown that the temperature dependencies of the resistivity obtained at different δ values obey the activation law up to the temperatures corresponding to the intense oxygen removal from a sample. The semiconductor‒semiconductor electronic transitions accompanied by a decrease in the activation energy have been observed with increasing temperature. It is demonstrated that the maximum thermoelectric power factor of 0.1 µW/(cm·K²) corresponds to a temperature of T = 800 K.