High-temperature electronic transport properties of Fe-doped YBaCo2O5+δ

The resistivity and Seebeck coefficients of YBaCo2−xFexO5+δ(0⩽x⩽0.8) were measured from room temperature (RT) to 800 °C. It was found that all compositions behave as p-type semiconductors in the temperature range of RT–300 °C. When temperature is above about 300 °C, both electrical resistivity and Seebeck coefficients increase with the increase of temperature due to oxygen desorption from the lattices. Fe doping tends to increase resistivity and Seebeck coefficients in all the temperature ranges measured. The calculated activation energy of conductivity is larger than that of thermopower in the semiconductor region, which means that the conduction mechanism may be determined as a small polaron hopping model.