Electrical Conductivity and Defect Structure of Calcium‐Doped Lanthanum Chromites

Electrical conductivity of calcium‐doped lanthanum chromites, , was determined as a function of composition, temperature, and oxygen partial pressure, , to determine its defect structure and understand its redox behavior. The conductivity was independent of and was proportional to the dopant concentration at high . The activation energy of conductivity was 0.12 to 0.14 eV and the mobility was 0.066 to 0.075 cm²/V/s in the temperature range of 900 to 1050°C, which was ascribable to small‐polaron hopping. Under reducing conditions, the conductivity decreased exponentially with decreasing and asymptotically approached a relationship. A simple point‐defect model, in which , , and were assumed as predominating defect species, was proposed to elucidate the conductivity variation with . The oxygen nonstoichiometry calculated based on the defect model was consistent with the reported thermogravimetric data, which verified the soundness of the model.