Thermal expansion behavior of La-doped (Ba0.5Sr0.5Co0.8Fe0.2)O3−δ cathode material

In this study, the thermal expansion behavior of the BSCF (Ba0.5Sr0.5Co0.8Fe0.2O3−δ) and La-doped BSCF, i.e., (Ba0.5Sr0.5)0.7La0.3Co0.8Fe0.2O3−δ (BSLCF30) was systematically examined. The thermal expansion rate of the sintered body increased rapidly at around 500 °C. It was found from the TG analysis that the oxygen vacancies formed around this temperature. When La is doped in the A-site of BSCF, more weight loss was observed over 500 °C compared to BSCF, which shows that La doping induces oxygen vacancies. Consequently, chemical expansion of the B-site cations occurred. Therefore, the thermal expansion coefficient (TEC) of BSLCF was much bigger than that of the BSCF. When the samples were heated and cooled in an Ar atmosphere, hysteresis of TEC was observed since re-oxidation cannot occur during cooling.