High temperature optical absorption spectroscopy at pure and Y-doped BaCeO 3

Abstract

The defect induced optical absorption has been investigated at different oxygen partial pressures and at temperatures up to 800°C for the high temperature protonic conductor BaCeO 3. Thin films of pure and 10 mol% Y-doped BaCeO 3 with thickness up to 11μm have been deposited on transparent MgO single crystal substrates by means of RF-magnetron sputtering techniques. After separating the different contributions to the optical absorption we have concentrated on the part of the spectra which is attributed to free small polarons. Under reducing external gas atmospheres these polarons are generated in the film along with oxygen vacancies and contribute to the electronic conductivity by their hopping processes. We report on time resolved measurements of the defect reaction kinetics after a change of the external gas atmosphere and investigate the influence of the doping atoms by comparing BaCe 0·9Y 0·1O 3 -δ and BaCeO 3. The observations are discussed in terms of the diffusion behavior of the oxygen vacancies. ©