| Popis: |
The objective of this work is to study the effect of lanthanum substitution by calcium on the physico‐chemical properties of La1−xCaxMnO3+y (0⩽x⩽1) solid solutions with a particular attention to the importance of the surface properties.XPS analysis reveal a significant changes in the La3d,4d; Ca2p; O1s and Mn2p characteristics as well as the excess of concentration with respect to the bulk resulting from the incorporation of Ca in La sublattice. The surface manganese deficit, which is systematically found for any substitution level x, is comparatively low for x = 0.6 and particularly important for solids with high amount of calcium.All these properties are correlated with surface catalytic performances in the methane combustion reaction. The best activities are observed with x⩽0.6. While the difference is barely perceptible for the samples with 0⩽x⩽0.4, a particular positive effect on the catalytic performances is found for x = 0.6. |
