Structural Characterization of LaCoO3 Thin Films Grown by Pulsed Laser Deposition

Thin films of crystallized LaCoO3 were grown on Si substrate by Pulsed Laser Deposition at different temperatures (750°C, 850°C and 1000°C). The structural characterization of the LaCoO3 thin films was done by combining several techniques: Scanning Electron Microscopy (SEM), Atomic Force Microscope (AFM), Transmission Electron Microscopy (TEM) and Grazing Incidence X-Ray Diffraction (GIXRD). The thin films crystallized in the expected rhombohedral phase whatever the deposition temperature, with an increase of crystallite size from 70 nm at 750°C to 100 nm at 1000°C, and an average thickness of the thin films of less than 200 nm. At 850°C and 1000°C, the thin films are crack-free, and with a lower number of droplets than the film deposited at 750°C. The grains of LaCoO3 film deposited at 850°C are columnar, with a triangular termination. At 1000°C, an intermediate layer of La2 Si2 O7 was observed, indicating diffusion of Si into the deposited film

Phase Separation in an SiCO Glass Studied by Transmission Electron Microscopy and Electron Energy-Loss Spectroscopy

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Structural investigation of temperature-induced phase transitions in HfV

HfV2O7 powders were prepared by means of thermal decomposition of a mixture of vanadyl and hafnyl oxalates in air at 973 K. The room temperature structure and its evolution with temperature was investigated using both electron microscopy (TEM and HREM) and powder diffraction (X-ray and neutron) techniques combined with DSC measurements. HfV2O7 exhibits two temperature-induced phase transitions between room temperature and 480 K. Over the highest transition (370 K), HfV2O7 crystallizes in a cubic system with a cell parameter of 8.75 Å and $Pa\bar{3}$ space group. A negative thermal expansion is observed in this high temperature phase and can be correlated to anisotropic oxygen atom displacements. On the other hand, the room temperature structure of HfV2O7 is also described in a cubic symmetry, but the existence of superstructure reflections leads to a cell parameter three times larger than for the high temperature structure (~ 26.25 Å). Moreover, HREM calculations have shown that the atomic positions, usually used to describe the superstructures of the ZrV2O7 compounds, cannot be used in the case of HfV2O7 at room temperature

Investigation of SiCO glasses synthesized with extensive ball milling

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Radiation effects on switching kinetics of three-dimensional ferroelectric capacitor arrays

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V-doped HfO2: thermal stability and vanadium valence

International audienceThe thermal stability under air of V-doped HfO2 powders was investigated by differential thermal analysis and thermogravimetric analysis (DTA-TG), while the oxidation state of the vanadium inserted in these powders was studied by electron energy loss spectroscopy (EELS). The valence of vanadium for powders prepared under reductive atmosphere was found to be 3+, as well as for powders prepared under neutral atmosphere, whereas powders prepared under air exhibit higher vanadium oxidation states (4+ and/or 5+). The main impurity detected by EELS in V-doped HfO2 powders was carbon. The powders elaborated under air are thermally and structurally stable up to 1000 K. For the V3+-doped powders, the thermal analysis showed the occurrence of irreversible transformations leading to different compounds

Characterisation of SiCN/SiCO Glasses via SEM and TEM

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Vanadium valency and hybridization in V-doped hafnia investigated by electron energy loss spectroscopy

PACS. 61.50.Nw Crystal stoichiometry – 71.28.+d Narrow-band systems; intermediate-valence solids – 78.70.Dm X-ray absorption spectra,