Description
Perovskite materials with the general formula ABO3 have shown significant potential in applications for catalysis and in electrochemical devices. The functional properties of these materials can be controlled by doping with selected metals, primarily d-block elements. This doping process involves introducing atoms on aliovalent or/and isovalent oxidation states into the perovskite lattice, replacing host atoms, and thereby altering the crystal structure, electron band configuration, and defect chemistry. These changes can modify the material's functional properties.
Materials based on the binary system CaTiO3-SrTiO3 modified with cobalt (Co) or iron (Fe) were prepared using the modified citrate method. For each dopant (Co, Fe), two series of materials were obtained, differing in the presence of a 5% deficiency in the Ca/Sr sublattice and calcium content. All compositions were obtained in form of powders after calcination at 900°C and characterized in terms of their structure (XRD, XAS), microstructure (SEM), and reducibility in an H2-containing atmosphere (TPR). The aim of this study was to investigate the incorporation of Co or Fe into the perovskite structure, the potential formation of oxides, and the effect of non-stoichiometry in the A sublattice (Sr/Ca) on the amount of dopant incorporated into the titanium sublattice.
The primary objective was to assess the impact of these modifications on the electronic and local structure of cobalt and iron dopants. Incorporating small amounts of a modifier into a perovskite structure presents unique analytical challenges, as traditional methods such as X-ray diffraction (XRD) often fail to detect these small quantities or identify amorphous phases within the material. To address these challenges, advanced techniques such as X-ray absorption spectroscopy (XAS)combined with temperature-programmed reduction (TPR), were employed. This approach provides a detailed understanding of the material's composition.
