Doping of lanthanum cobaltite by Mn: thermal, magnetic, and catalytic effect

Great differences in crystallographic phases, magnetic properties, and catalytic activity were detected in lanthanum cobaltite and cobaltite modified with the insertion of 10 wt.% of Mn. Atomic absorption spectroscopy, BET area measurements, XRD analysis, TPR, and FT-IR suggest that the total insertion of manganese in the LaCoO₃ structure is successful. Thermal stability is reached for LaCo_0.90Mn_0.10O₃ up to 973 K without loss of the perovskite structure. The magnetic properties of the as-grown compounds are maintained after a first reduction process up to 723–773 K, while presence of segregated phases is observed after reduction at 973 K. The catalytic activity evaluated in the total combustion of acetyl acetate shows a decrease in the ignition temperature, i.e. an increase in the catalytic activity for the LaCo_0.90Mn_0.10O₃ perovskite. A significant enhancement in the catalytic activity expressed as intrinsic activity, mol m⁻² h⁻¹, with the manganese substitution was found.