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We report on electrical resistivity, magnetoresistance (MR) and Hall effect measurements in four non-superconducting BaFe2−xTMxAs2 (TM = Mn, Cu and Ni) single crystals with small values of the chemical substitution x. The spin density wave (SDW) ordering that occurs in these systems at temperatures T ∼ (120 -140) K, in close vicinity to a tetragonal/orthorhombic transition, produces significant modifications in their magneto-transport properties. While in the magnetically ordered phase the MR is positive and its magnitude increases with decreasing temperatures, in the paramagnetic regime the MR becomes vanishingly small. Above the spin density wave transition temperature (TSDW) the Hall coefficient RH is negative, small and weakly temperature dependent, but a remarkable change of slope occurs in the RH versus T curves at T = TSDW. The Hall coefficient amplitude, while remaining negative, increases steadily and significantly as the temperature is decreased below TSDW and down to T = 20 K. The qualitative behavior of both MR and Hall coefficient is weakly dependent on the chemical substitution in the studied limit. The experiments provide strong evidence that scattering of charge carriers by magnetic excitations has to be taken into account to explain the behavior of the resistivity, magnetoresistance and Hall effect in the ordered phase of the studied compounds. Effects of multiple band conduction also must be considered for a complete interpretation of the results.

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We report in-field kinetic energy results in the temperature region closely below the transition temperature of two differently prepared polycrystalline samples of the superconducting cuprate SmBa2Cu3O 7−δ . The kinetic energy was determined from magnetization measurements performed above the irreversibility line defined by the splitting between the curves obtained according the ZFC and FC prescriptions. The results are analyzed in the intermediate field regime where the London approximation can be used for describing the magnetization. From the analysis, estimations were carried out for the penetration depth and the upper critical field of the studied samples.The difference between the kinectic energy magnitudes for the two studied samples is ascribed to effects from granularity.

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We report the first Raman spectra for the vanadates with chemical formula M V 2 O 6 (M =Mn, Co, Ni, Zn) crystallized in a columbite-type structure (Pbcn space group). The columbite-type structure, which is quite unusual for the compounds M V 2 O 6 , was obtained by synthesis at high temperature and pressure from precursor powder samples in either P 1 or C2/m structures. The cell parameters, interatomic distances, and distortion indexes of the octahedra in the Pbcn structure, were obtained from the Rietveld refinement of powder Xray diffraction patterns measured at room temperature for each sample. The Raman modes were obtained from high quality spectra recorded in the range of wavenumbers between 50 and 1170 cm −1 ; these were assigned by comparison with the known spectra of the isostructural niobates M Nb 2 O 6 . Common sequences of peaks can be identified in the Raman spectra of all the studied samples, but the position of those peaks in wavenumberω does not follow the behavior that is expected from looking only at the interatomic distances between the atoms involved in the vibration. The influence of the electronegativity of the atoms M in the force constants of the V-O bonds is proven in the evolution of the A g Raman mode observed at the highest wavenumber.

Poster Sessions C497 coefficient to those of the closer components and be chemically compatible with them.SOFCs operate at high termperatures under either oxidising or reducing atmospheres over a long period of time. This can create different problems such as interface reactions which could promote the formation of insulating phases, limiting their long-term stability [1]. In light of this, the idea is to find new materials that are very stable at high temperatures and have the properties described above.Here we report the investigation of the family of pyrochlores of general formula A 2 B 2 O 7 (where A is a trivalent ion, usually a rare earth, and B is a tetravalent ion) which are known to exhibit oxygen ion conductivities of the order of 10-2 S/cm at 1000 º C, making them promising candidates as electrolytes. In particular we have focused on Ln 2 Zr 2 O 7 (Ln= Lanthanide) whose structure is mainly governed by the ion size difference between Ln 3+ and Zr 4+ [5]. These materials have the properties needed to be a good electrolyte (high melting point, high thermal expansion coefficient, low thermal conductivity, high thermal stability and high electrical conductivity) in SOFCs [6]. Among the rare earth zirconates, Ce 2 Zr 2 O 7 bears additional interest due to the catalytic application of the CeO 2 -ZrO 2 in several chemical processes in industry and automobiles [7].We have study the stability in air of the solid solutions La 2 -x Ce x Zr 2 O 7 and Gd 2-x Ce x Zr 2 O 7 and the effect of the Ce-doping on the conductivity. The X-ray diffraction studies show, that the La-series keeps the pyrochlore structure up to x = 0.5, while the Gd one adopts the fluorite structure. These results will be correlated to the conductive behavior of these materials.[ Mixed oxide-ionic and electronic conducting ceramics (MIECs) will become increasingly important for future environmentally friendly ("green") societies, because the MIECs are used as materials for oxygen separation membranes and cathodes of solid-oxide fuel cells (SOFCs). Oxygen is an important reactant in the industrial chemical processes and air is usually utilized as the oxygen source due to the cost problem. For lower temperature devices, novel MIECs with higher oxide-ion diffusivity are required. For this purpose, it is of vital importance to investigate the oxide-ion diffusion mechanism at an atomic scale. Bourgogne, 21078 Dijon, b ESRF, 38043 Grenoble (France). E-mail: ioana.popa@u-bourgogne.fr Low chromium ferritic steels have been extensively studied for applications in power generating plant life time. Formation of dense, thick, and adherent chromia (Cr 2 O 3 ) layer on stainless steel, which is considered like a good way to increase the oxidation resistance, is closely related to many parameters such as chromium content, temperature, oxidizing atmosphere, cycles frequency and time of exposure [1][2][3]. For grades with 9%Cr such as T/P91, the chromium content is not enough to fulfil the protective action by creating a continuous chromia scale over 600°C. As...

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