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- Saxena, SK, et al.
(författare)
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Stability of perovskite (MgSiO3) in the Earth's mantle
- 1996
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Ingår i: SCIENCE. - 0036-8075. ; 274:5291, s. 1357-1359
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Tidskriftsartikel (refereegranskat)abstract
- Available thermodynamic data and seismic models favor perovskite (MgSiO3) as the stable phase in the mantle. MgSiO3 was heated at temperatures from 1900 to 3200 kelvin with a Nd-YAG laser in diamond-anvil cells to study the phase relations at pressures fr
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| 5. |
- Andrault, D, et al.
(författare)
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Study of partial melting at high-pressure using in situ X-ray diffraction
- 2006
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Ingår i: High Pressure Research. - : Informa UK Limited. - 0895-7959 .- 1477-2299. ; 26:3, s. 267-276
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Tidskriftsartikel (refereegranskat)abstract
- The high-pressure melting behavior of different iron alloys was investigated using the classical synchrotron-based in situ X-ray diffraction techniques. As they offer specific advantages and disadvantages, both energy-dispersive (EDX) and angle-dispersive (ADX) X-ray diffraction methods were performed at the BL04B1 beamline of SPring8 (Japan) and at the ID27-30 beamline of the ESRF (France), respectively. High-pressure vessels and pressure ranges investigated include the Paris- Edinburgh press from 2 to 17GPa, the SPEED-1500 multi-anvil press from 10 to 27 GPa, and the laser-heated diamond anvil cell from 15 to 60 GPa. The onset of melting (at the solidus or eutectic temperature) can be easily detected using EDX because the grains start to rotate relative to the X-ray beam, which provokes rapid and drastic changes with time of the peak growth rate. Then, the degree of melting can be determined, using both EDX and ADX, from the intensity of diffuse X-ray scattering characteristic of the liquid phase. This diffuse contribution can be easily differentiated from the Compton diffusion of the pressure medium because they have different shapes in the diffraction patterns. Information about the composition and/or about the structure of the liquid phase can then be extracted from the shape of the diffuse X-ray scattering.
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| 6. |
- Azdouz, M., et al.
(författare)
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Crystal chemistry, Rietveld refinements and Raman spectroscopy studies of the new solid solution series: Ba3−xSrx(VO4)2 (0≤x≤3)
- 2010
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 498:1, s. 42-51
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Tidskriftsartikel (refereegranskat)abstract
- The new solid solution series Ba3-xSrx(VO4)(2) (0 <= x <= 3) has been synthesized and studied by a combination of X-ray powder diffraction and Raman vibrational spectroscopy. This continuous solid solution crystallise in the hexagonal system with R (3) over barm space group. The structure has been determined at room temperature from X-ray diffraction by the Rietveld method analysis. It is formed by a 3D network of (Ba/Sr)((1))(VO4)(2)(4-) layers linked into a crystal network by (Ba/Sr)(2+)((2)) cations. The vibrational spectra of this crystalline orthovanadate solid solution series are interpreted by means of factor group analysis in terms of space group R (3) over barm (D-3d(5)). Assignments of the V-O vibrational stretching and bending modes, as well as some of the external modes, have been made. While all the modes show a monotonous shift as a function of the composition x, a break in the curves of intensities, full width at half maximum and band areas as a function of x is observed and attributed to the statistical distribution of Ba and Sr ions in the same crystallographic sites.
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| 7. |
- Bih, H., et al.
(författare)
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Preparation and electrical conductivity of NaF-Li2O-WO3-P2O5 glasses
- 2009
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Ingår i: Journal of Optoelectronics and Advanced Materials. - 1454-4164 .- 1841-7132. ; 3:9, s. 959-963
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Tidskriftsartikel (refereegranskat)abstract
- Several studies have been reported on lithium phosphate glasses to which lithium halides and lithium sulphate have been added However, there has been no experimental results for the introduction of sodium fluoride into the lithium tungsten phosphate network How specifically this feature - mixed alkali in the presence of fluorine ion - influences ion transport in the glasses is unclear. This work concerns the investigation of ion transport behaviour of NaF containing lithium tungsten phosphate glasses in order to understand better the role of NaF in the ionic cation transport Glasses obtained in the system 0.5[x(2NaF)-(1-x)Li2O]-0.5[0.25(WO3)(2)-0.75P(2)O(5)] were investigated The glass samples have been characterised using powder X-ray diffraction (XRD), thermal analysis, density and impedance spectroscopy X-ray diffraction and thermal studies have confirmed that these glasses can be formed in the range x = 0 to 1 The mixed alkali glasses have shown higher activation energies and lower conductivities compared to single alkali doped glasses and this has been attributed to a mixed alkali influence on the electrical conduction in these systems.
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| 10. |
- Choudhury, Debraj, et al.
(författare)
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Tuning of dielectric properties and magnetism of SrTiO3 by site-specific doping of Mn
- 2011
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 84:12, s. 125124-
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Tidskriftsartikel (refereegranskat)abstract
- Combining experiments with first-principles calculations, we show that site-specific doping of Mn into SrTiO(3) has a decisive influence on the dielectric properties of these doped systems. We find that phonon contributions to the dielectric constant invariably decrease sharply on doping at any site. However, a sizable, random dipolar contribution only for Mn at the Sr site arises from a strong off-centric displacement of Mn in spite of Mn being in a non-d(0) state; this leads to a large dielectric constant at higher temperatures and gives rise to a relaxor ferroelectric behavior at lower temperatures. We also investigate magnetic properties in detail and critically reevaluate the possibility of a true multiglass state in such systems.
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