C. Oliva et L. Forni, EPR investigation of superparamagnetism in nanometric-size LaFeO3 +/-deltaand La2NiO4 +/-delta perovskites, APPL MAGN R, 20(4), 2001, pp. 531-538
Two LaFeO3 +/- delta and La2NiO4 +/- delta catalysts characterized by high
thermal stability and phase purity have been prepared. Scanning electron mi
croscopy analysis showed that they consisted of 20-60 nm spheroids, general
ly clustered in one order of magnitude larger particles. Electron paramagne
tic resonance (EPR) spectroscopy showed that both samples possess superpara
magnetic properties, connected with ca. 20 nm diameter particles. Furthermo
re, the EPR patterns were broader in La2NiO4 +/- delta, than in LaFeO3 +/-
delta, indicating a greater amount of local disorder in the former. This wa
s attributed to the presence of more oxygen vacancies in the Ni-based than
in the Fe-based sample, in agreement with what was elsewhere hypothesized o
n the basis of catalytic properties of the two samples for the flameless co
mbustion of methane.