Study of oxygen desorption from substituted perovskites: New possibilities through fast intermittent temperature-programmed desorption

摘要

A differential desorption technique, named intermittent temperature-programmed desorption (ITPD), has been used to get new insights into the properties of La1-xSrxCo0.8Fe0.2O3-delta perovskites. The apparent activation energy of desorption (E-app) and the frequency factor (v) were calculated from ITPD data, for the two distinct oxygen species desorbing from perovskite at temperatures lower than 400 degrees C. The low values (about 10(7)-10(8) s(-1)) obtained for V-app indicated that re-adsorption occurred during the TPD process and therefore that E-app is equal to the Heat of adsorption (E=-Delta 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.