Abstract
A differential desorption technique, named intermittent temperature-programmed desorption (ITPD), has been used to get new insights into the properties of La 1 − x Sr x Co 0.8Fe 0.2O 3 − δ perovskites. The apparent activation energy of desorption ( E app) and the frequency factor ( ν) were calculated from ITPD data, for the two distinct oxygen species desorbing from perovskite at temperatures lower than 400 °C. The low values (about 10 7–10 8 s − 1 ) obtained for ν app indicated that re-adsorption occurred during the TPD process and therefore that E app is equal to the Heat of adsorption ( E = − Δ H). The first oxygen species, related to lower desorption temperatures, exhibits a distribution of E from 105 to 125 kJ mol − 1 . The second one, related to higher desorption temperatures, corresponds to E = 146 ± 4 kJ mol − 1 and 139 ± 5 kJ mol − 1 , for x = 0.2 and x = 0.3, respectively. The relative amounts of these species contributing to the desorption peak are dependent upon Sr content in the perovskite.
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