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Microstructural evolution of a Solid Oxide Electrolyser Cell (SOEC) La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) anode is investigated using 3D reconstruction techniques both on a reference and a long-term tested cell. In this framework, reconstructions have been obtained from focused ion beam-scanning electron microscopy and synchrotron X-ray nano-tomography techniques. Microstructural properties extracted from the 3D reconstructions exhibit a slight evolution during the test. Synchrotron X-ray Absorption Spectroscopy (XAS) was also performed, and a modification of the cobalt oxidation state is found. LSCF conductivity decrease due to the change in Co mixed valence has been discussed. Evolutions of both morphological parameters and electrical conductivity were introduced in an in-house micro model to evaluate their impacts on the electrode degradation.

We performed new diffraction experiments to clarify the equation of state (EoS) of stishovite after we suspected systematic errors in previous experimental reports. Using diamond anvil cells, we repeated both single-crystal X-ray diffraction measurements under hydrostatic conditions and powder diffraction measurements using the laser-annealing technique and NaCl pressure medium. The major improvement is the increase in precision of the pressure determination using the quartz and NaCl equations of state. Using both sets of data, the stishovite bulk moduli were refined to K0= 309.9(1.1) GPa and K'0= 4.59(0.23). We also reinvestigated the mechanism of the phase transformation to the CaCl2-structured polymorph of SiO2at about 60 GPa. We confirm no volume discontinuity at the transition pressure, but the CaCl2form appears slightly more compressible than the rutile-structured form of SiO2. This change in compression behavior is used for quantitative analyses of the spontaneous strains of the pressure-induced phase transition.

The structural behavior of an Am0.5Cm0.5alloy has been recently investigated at the High-Pressure-ID30 beamline of the ESRF. The use of synchrotron radiation, diamond anvil cell and 2D detector has allowed us to collect very high quality diffraction patterns up to pressures of 65 GPa. The atmospheric pressure double hexagonal close packed (P63/mmc) structure transforms around 10 GPa to a face centered cubic (Fm3m) phase. Like for pure Am metal1-2), we find that the pressure induced derealization of the 5f electrons in Am0.5Cm0.5occurs in two distinct stages rather than a single step: at 21 GPa the cubic phase converts to a face centered orthorhombic (Fddd) structure, which transforms into a primitive orthorhombic structure (Pnma) at 45 GPa. The latter phase is stable to at least 65 GPa. Work is presently underway to determine whether the elements Cm and Cf behave similarly under pressure.