17 - Reactivity of individual components in ceria-perovskite composites: Experimental evidence and thermodynamic evaluation

Abstract

The chapter discusses the reactivity between initial components in the ceria-perovskite composites during their fabrication. It is shown that a complex approach including the application of X-ray phase and Rietveld structural analyses, extended X-ray absorption fine structure technique, X-ray photoelectron spectroscopy, analytical microscopy, and thermogravimetric analysis is required to achieve reliable conclusions about the chemical stability of individual components in composite materials, as their modification could have a strong impact on functional properties of materials. The discussion presented in the chapter is based on the experimental data obtained for manganates, cobaltites, nickelates, and ferrites with perovskite structure and composites on their basis; and with the aid of thermodynamic calculations it is extended toward chemical reactivity in composites composed of ceria and perovskites containing selected 3d-, 4d-, and 5d- transition metal cations on the B-sublattice. The results obtained indicate that a higher chemical stability of individual components in the composites on the basis of ABO3 (B = Ti, V, Nb, Mo, Ta, and W) and pure/Gd,Sm-doped CeO2 is expected during their fabrication. Factors defining the reactivity of components in the ceria-perovskite composites have been discussed. An impact of elements redistribution on conductivity and redox behavior of composites is briefly illustrated.