Second order self-organized pattern of terbium–scandium–aluminum garnet and terbium–scandium perovskite eutectic

International audienceTb3Sc2Al3O12 has been grown as a crystal showing high Faraday effect. A self-organized pattern, of directionally formed eutectic, has been observed at the edge of the Tb3Sc2Al3O12 microcrystals grown by the micro-pulling down method. Binary (Tb3Sc2Al3O12/TbScO3) and ternary eutectic (depending on the pulling rate and the composition) are formed at the edges showing a highly packed pseudo-hexagonal spot pattern (over large areas) in the cross section and a rod pattern (length up to 200 μm) in the longitudinal section. The size of the spot pattern can be controlled by the pulling rate. The observed arrays can be suitable for various photonic devices

Evaluation of MAX-DOAS aerosol retrievals by coincident observations using CRDS, lidar, and sky radiometer inTsukuba, Japan

Coincident aerosol observations of multi-axis differential optical absorption spectroscopy (MAX-DOAS), cavity ring-down spectroscopy (CRDS), lidar, and sky radiometer were conducted in Tsukuba, Japan, on 5–18 October 2010. MAX-DOAS aerosol retrieval (for aerosol extinction coefficient and aerosol optical depth at 476 nm) was evaluated from the viewpoint of the need for a correction factor for oxygen collision complexes (O₄ or O₂–O₂) absorption. The present study strongly supports this need, as systematic residuals at relatively high elevation angles (20 and 30°) were evident in MAX-DOAS profile retrievals conducted without the correction. However, adopting a single number for the correction factor (<i>f</i>_O₄ = 1.25) for all of the elevation angles led to systematic overestimation of near-surface aerosol extinction coefficients, as reported in the literature. To achieve agreement with all three observations, we limited the set of elevation angles to &le;10° and adopted an elevation-angle-dependent correction factor for practical profile retrievals with scattered light observations by a ground-based MAX-DOAS. With these modifications, we expect to minimize the possible effects of temperature-dependent O₄ absorption cross section and uncertainty in DOAS fit on an aerosol profile retrieval, although more efforts are encouraged to quantitatively identify a physical explanation for the need of a correction factor

Croissance de fibres polycristallines de composition eutectique AI2_2O3_3/Y3_3AI5_5O12{12} pour renforcement de composite

Eutectic fiber belongs to the Y$_2$O$_3$Al$_2$O$_3$ system were grown using Laser Heated Pedestal growth technique. We have controlled the fiber and diameter shape during the growth process. The interface of the melting zone was been plane. The fibers length was about few centimetre and are cracks and defects free. The eutectic fibers have high temperature strength properties, it was 577 MPa at 1500°C

Solvothermal processes and the synthesis of nitrides

Nitrides constitute an important class of materials due to their physical properties. In this way, all processes related to their synthesis or shaping are of relevant interest. A solvothermal process can be described as a reaction between precursors in a close system in the presence of a solvent and at a temperature higher than the boiling point of the solvent, with pressure being consequently involved. Depending on the pressure and temperature, the solvent is in sub- or supercritical conditions. The system precursors/solvent can be either homogeneous or heterogeneous. Concerning nitrides, solvothermal processes have been mainly developed in three domains: 1. the preparation of novel compositions / 2. the elaboration of nanocrystallites well defined in size and morphology / 3. the crystal-growth of functional nitrides such as GaN. Considering the synthesis of novel nitrides, different solvothermal reactions can be used versus the nitriding agent (N3- or N./GHPR_A_350185_O_XML_IMAGES/GHPR_A_350185_O_ILM0001.gif ) and the nature of the solvent (nitriding solvent or non-reactive solvent). Different examples will be given and the potentialities of solvothermal processes in the preparation of novel nitrides will be discussed