The Experts below are selected from a list of 39 Experts worldwide ranked by ideXlab platform
Anne M Hofmeister - One of the best experts on this subject based on the ideXlab platform.
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thermal diffusivity of Olivine Group minerals at high temperature
American Mineralogist, 2006Co-Authors: Maik Pertermann, Anne M HofmeisterAbstract:Thermal diffusivity ( D ) data from 12 oriented single crystals and seven polycrystalline samples of Olivine Group minerals were acquired with the laser-flash method at temperatures ( T ) of up to ~1500 °C. Samples included forsterite, Fe-Mg binary Olivines, sinhalite, and chrysoberyl; specimens were characterized using infrared spectroscopy and electron microprobe analysis. Crystal orientation and chemistry both affect D . For our single crystals, D [100] > D [001] > D [010] at all temperatures. Thermal diffusivity decreases with increasing T and becomes virtually constant at high temperatures. At room temperature, D [001] of pure forsterite has the highest observed values, but substitution of a small amount of Co in forsterite (0.3 wt% CoO) lowers D by ~20%. Substitution of ~10% Fe for Mg in forsterite, as in typical mantle Olivine, lowers D by ~50%. At room temperature, mantle Olivine has D = 3.25, 1.66, and 2.59 mm2/s for the [100], [010], and [001] orientations, respectively. The values decrease to 0.93–0.87 mm2/s at 790–985 °C for [100], 0.54–51 mm2/s at 590–740 °C for [010] and 0.83–0.79 mm2/s at 740–890 °C for [001]. Two dunite samples have D of 0.55–0.56 mm2/s at 890–1080 °C, showing the effect of preferred orientation of grains dominated by [010]. Thermal diffusivity of polycrystalline samples is controlled by the large amounts of Olivine present; minor phases offset the curves for D ( T ) from the value of the Olivine mineral. Our laser-flash measurements isolate the phonon component of heat transfer from radiative transfer and show that the phonon contribution becomes nearly constant for the high temperatures expected in the mantle. The other microscopic component (diffusive radiative transfer) depends strongly on temperature and this temperature dependence likely exerts greater control on mantle convection.
Christian Masquelier - One of the best experts on this subject based on the ideXlab platform.
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magnetic structures of the triphylite lifepo4 and of its delithiated form fepo4
Chemistry of Materials, 2003Co-Authors: J Rodriguezcarvajal, Sébastien Patoux, Christian MasquelierAbstract:The magnetic structures of LiFePO4 and of its delithiated form FePO4 (triphylite, Olivine Group, space Group Pnma) have been solved using neutron diffraction on polycrystalline samples. Both compounds show antiferromagnetic behavior below 52 K for LiFePO4 (Fe2+) and below 125 K for FePO4 (Fe3+), characterized by the appearance of extra peaks in the neutron diffraction patterns below the Neel temperature. These magnetic reflections are indexed with a propagation vector k = (0,0,0). The magnetic moments of the four iron atoms present in the unit cell are oriented along [010] for LiFePO4 and mostly along [100] (with a small component along [010]) for FePO4. The magnetic structures and the differences in the Neel temperatures are discussed in terms of super and super-super exchange intractions and of anisotropy of Fe2+. A comparison is made with other Olivine compounds with similar cation distribution.
Maik Pertermann - One of the best experts on this subject based on the ideXlab platform.
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thermal diffusivity of Olivine Group minerals at high temperature
American Mineralogist, 2006Co-Authors: Maik Pertermann, Anne M HofmeisterAbstract:Thermal diffusivity ( D ) data from 12 oriented single crystals and seven polycrystalline samples of Olivine Group minerals were acquired with the laser-flash method at temperatures ( T ) of up to ~1500 °C. Samples included forsterite, Fe-Mg binary Olivines, sinhalite, and chrysoberyl; specimens were characterized using infrared spectroscopy and electron microprobe analysis. Crystal orientation and chemistry both affect D . For our single crystals, D [100] > D [001] > D [010] at all temperatures. Thermal diffusivity decreases with increasing T and becomes virtually constant at high temperatures. At room temperature, D [001] of pure forsterite has the highest observed values, but substitution of a small amount of Co in forsterite (0.3 wt% CoO) lowers D by ~20%. Substitution of ~10% Fe for Mg in forsterite, as in typical mantle Olivine, lowers D by ~50%. At room temperature, mantle Olivine has D = 3.25, 1.66, and 2.59 mm2/s for the [100], [010], and [001] orientations, respectively. The values decrease to 0.93–0.87 mm2/s at 790–985 °C for [100], 0.54–51 mm2/s at 590–740 °C for [010] and 0.83–0.79 mm2/s at 740–890 °C for [001]. Two dunite samples have D of 0.55–0.56 mm2/s at 890–1080 °C, showing the effect of preferred orientation of grains dominated by [010]. Thermal diffusivity of polycrystalline samples is controlled by the large amounts of Olivine present; minor phases offset the curves for D ( T ) from the value of the Olivine mineral. Our laser-flash measurements isolate the phonon component of heat transfer from radiative transfer and show that the phonon contribution becomes nearly constant for the high temperatures expected in the mantle. The other microscopic component (diffusive radiative transfer) depends strongly on temperature and this temperature dependence likely exerts greater control on mantle convection.
J Rodriguezcarvajal - One of the best experts on this subject based on the ideXlab platform.
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magnetic structures of the triphylite lifepo4 and of its delithiated form fepo4
Chemistry of Materials, 2003Co-Authors: J Rodriguezcarvajal, Sébastien Patoux, Christian MasquelierAbstract:The magnetic structures of LiFePO4 and of its delithiated form FePO4 (triphylite, Olivine Group, space Group Pnma) have been solved using neutron diffraction on polycrystalline samples. Both compounds show antiferromagnetic behavior below 52 K for LiFePO4 (Fe2+) and below 125 K for FePO4 (Fe3+), characterized by the appearance of extra peaks in the neutron diffraction patterns below the Neel temperature. These magnetic reflections are indexed with a propagation vector k = (0,0,0). The magnetic moments of the four iron atoms present in the unit cell are oriented along [010] for LiFePO4 and mostly along [100] (with a small component along [010]) for FePO4. The magnetic structures and the differences in the Neel temperatures are discussed in terms of super and super-super exchange intractions and of anisotropy of Fe2+. A comparison is made with other Olivine compounds with similar cation distribution.
G Ouvrard - One of the best experts on this subject based on the ideXlab platform.
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structure refinement and magnetic behaviour of the only selenide in the Olivine Group family mn2sise4
Journal of Alloys and Compounds, 1995Co-Authors: Stephane Jobic, Bode F Nan, Le P Boterf, G OuvrardAbstract:Abstract Mn2SiSe4 has been synthesized at 800°C. This compound cristallizes in the Olivine-type structure with the cell parameters a = 13.3066(8)A˚, b = 7.7780(5)A˚andc = 6.2451(3)A˚ in the Pnma space Group. To date this structure type had been only reserved for oxides and sulfides. We report here the crystal structure determination of the first selenide with Olivine structure. The magnetic measurements from 5 K to room temperature suggest the existence of preponderant antiferromagnetic interactions.
