High-temperature stability of thermoelectric Ca₃Co₄O₉ thin films

An enhanced thermal stability in thermoelectric Ca₃Co₄O₉ thin films up to 550-°C in an oxygen rich environment was demonstrated by high-temperature electrical and X-ray diffraction measurements. In contrast to generally performed heating in helium gas, it is shown that an oxygen/helium mixture provides sufficient thermal contact, while preventing the previously disregarded formation of oxygen vacancies. Combining thermal cycling with electrical measurements proves to be a powerful tool to study the real intrinsic thermoelectric behaviour of oxide thin films at elevated temperatures.