An investigation of non-stoicheiometry in the systems SrFeO_{3 –y}and SrCoO_{3 –y}by iron and cobalt K-edge extended X-ray absorption fine structure spectroscopy

Synthesis and characterization of the oxygen-deficient perovskite BaFe0.9-xY0.1CoxO3-δ (0 ≤x≤ 0.15)

“…XRD analysis of a sample of BaFe0.9Y0.1O3-δ that had been slowly cooled from 1373 K to room temperature in air showed the formation of a single, perovskite-like phase. TGA showed the composition at 298 K in air to be BaFe0.9Y0.1O2.62, which is very close to that reported previously [3]. The XRD pattern of our sample was indexed in a cubic unit cell (S.G. Pm3m): the results of a Rietveld [12] analysis of the pattern are shown in Figure 1.…”

“…Thermal expansion is difficult to predict quantitatively for a defect-rich solid and although transition-metal cations are often associated with catalytic activity it is again difficult to predict the behavior of a particular compound. It has therefore been necessary to adopt a somewhat empirical approach in the search for new electrode materials, although perovskites containing iron or cobalt have often been to the fore because these two elements undergo an extensive redox chemistry between the oxidation states +2, +3 and +4, with mixed-valence states being common [2][3][4][5][6]. If a perovskite-related oxide is anion deficient there is a tendency for the vacancies to adopt an ordered arrangement, either locally or in a periodic manner, with the latter scenario leading to, for example, the brownmillerite structure.…”

Anisotropy in the thermal hysteresis of resistivity and charge density wave nature of single crystal SrFeO3-δ: X-ray absorption and photoemission studies

“…The insets present corresponding EXAFS k 2 χ data. The Fe K -edge EXAFS spectra include main FT features ( A , B and C ) that correspond to the NN bond lengths of Fe-O, Fe-Sr and Fe-Fe, respectively, in the SrFeO 2.81 crystal 3, 39, 40 . To obtain detailed information about the temperature dependence of the local structure around the Fe atoms, Fig.…”

SrCo1−xSbxO3−δ perovskite oxides as cathode materials in solid oxide fuel cells

“…However, if the samples are slowly cooled from the reaction temperature (∼1000 • C), a hexagonal polymorph is obtained, with a structure related to that of 2H-BaNiO 3 [4]. Further studies have demonstrated that the crystal structure of the hexagonal phase could be described as a face-sharing arrangement of CoO 6 octahedra [5][6][7] and that this polymorph is, in fact, slightly Co-deficient, acquiring the Sr 6 Co 5 O 15 chemical stoichiometry [8]. This hexagonal structure has shown to be almost non-oxygen permeable [1].…”