V. Procházka

Bentonite/Iron Oxide Composites: Preparation and Characterization by Hyperfine Methods

Bentonite/iron oxide system is prepared by isothermal calcination of powder composed of bentonite clay and precursor containing ferric acetate. This preparation technique enables one to get the composite material directly, that is, iron oxide particles embedded in a bentonite matrix. Calcination temperature is varied from 320°C to 700°C. The resulting series of samples is characterized by local methods based on hyperfine interactions: 57Fe nuclear magnetic resonance (NMR) and the Mössbauer spectroscopy. The results show that the phase composition changes significantly in dependence on calcination temperature. The amount of maghemite phase rapidly increases up to °C and decreases abruptly for higher than 460°C.

EXAFS study of LaMn1-xCoxO3 compounds

A systematic study of cobalt environment in the LaMn1-xCoxO3LaMn1-xCoxO3 perovskite series by means of X-ray absorption spectroscopy in the EXAFS range is reported. The spectra were measured at the KK edge of Co on powder samples at room temperature and analysed using multiple scattering paths calculated with the FEFF8 computer program. The next neighbor oxygen shell of cobalt shows a decrease of the distance from the central ion with increasing Co doping. This corresponds to an increased oxidation level of 3d ions. An information on the distortion of the oxygen octahedra and the Debye–Waller factor is discussed.

EXAFS study of LaMn1-xCoxO3LaMn1-xCoxO3 compounds

A systematic study of cobalt environment in the LaMn1-xCoxO3LaMn1-xCoxO3 perovskite series by means of X-ray absorption spectroscopy in the EXAFS range is reported. The spectra were measured at the KK edge of Co on powder samples at room temperature and analysed using multiple scattering paths calculated with the FEFF8 computer program. The next neighbor oxygen shell of cobalt shows a decrease of the distance from the central ion with increasing Co doping. This corresponds to an increased oxidation level of 3d ions. An information on the distortion of the oxygen octahedra and the Debye–Waller factor is discussed.

EXAFS study of compounds

A systematic study of cobalt environment in the LaMn1-xCoxO3LaMn1-xCoxO3 perovskite series by means of X-ray absorption spectroscopy in the EXAFS range is reported. The spectra were measured at the KK edge of Co on powder samples at room temperature and analysed using multiple scattering paths calculated with the FEFF8 computer program. The next neighbor oxygen shell of cobalt shows a decrease of the distance from the central ion with increasing Co doping. This corresponds to an increased oxidation level of 3d ions. An information on the distortion of the oxygen octahedra and the Debye–Waller factor is discussed.