Results 161 to 170 of about 4,525 (206)

The first-principle studies of the crystal phase transitions: Fd3m-MgAl2O4→F4-3m-MgAl2O4

Physica B: Condensed Matter, 2011
Abstract Magnesium aluminum spinel (MgAl 2 O 4 ) is a major constituent of the shallow upper mantle. It is of great geophysical importance to explore its physical properties under high pressure and temperature. The first-principle density functional theory (DFT) with the plane wave along with pseudopotential was employed to obtain the total energy ...
Liang Zhang, Guang-Fu Ji, Feng Zhao, Chuan-Min Meng, Dong-Qing Wei   +4 more
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Effect of additives on the sintering of MgAl2O4

Journal of Alloys and Compounds, 2014
Abstract The effect of additives on the densification of stoichiometric spinel was investigated. SiO 2 , CaCO 3 and TiO 2 are used as additives to spinel composition in the range of 1–4 wt%. Densification behavior is investigated by dilatometry measurement and the sintered body is characterized in terms of microstructure, phase formation and change
Taehyung Kim, Donghyun Kim, Shinhoo Kang
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Shock effects in MgAl2O4-spinel

Physics and Chemistry of Minerals, 1983
Shock recovery experiments on synthetic MgAl2O4-spinel samples in the pressure range 25.5 to 50.5 GPa have been performed in order to examine the effects of shock waves on this material. The shocked samples were subsequently studied in the transmission electron microscope.
Helmut Sch�fer, Wolfgang Friedrich M�ller, Ulrich Hornemann   +2 more
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Defect processes in MgAl2O4 spinel

Solid State Sciences, 2008
Abstract In perfect normal MgAl 2 O 4 spinel the Mg 2+ ions occupy tetrahedral 8a sites and Al 3+ ions occupy octahedral 16d sites. In reality some cations are exchanged between the cation sublattices forming pairs of antisite defects and thus a degree of “inversion”.
Ball, J. A., Murphy, S. T., Grimes, R. W., Bacorisen, D., Smith, R., Uberuaga, B. P., Sickafus, K. E.   +6 more
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Fracture of single crystal MgAl2O4

Journal of Materials Science, 1980
The fracture of single crystal, stoichiometric MgAl2O4 spinel, was investigated for the (1 0 0), (1 1 0), and (1 1 1) from room temperature to 1500° C. Two regions of fracture behaviour were observed; a low temperature elastic region where K lc decreased with increasing temperature, and an elevated temperature region where K lc increased rapidly with ...
R. L. Stewart, R. C. Bradt
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Lattice vibrations of MgAl2O4 spinel

Journal of Physics and Chemistry of Solids, 1973
Abstract Raman spectra have been measured on oriented single crystals of MgAl2O4 spinel. The fundamental frequencies are A1g = 772, Eg = 410, and T2g = 671, 492 and 311 cm−1. A Kramers-Kronig analysis of the reflectance spectrum of spinel yields the i. r. -active vibrations T1u = 670, 485, 428 and 305 cm−1.
M.P. O'Horo, A.L. Frisillo, W.B. White
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On Infrared Intensities of Spinel, MgAl2O4

Bulletin of the Chemical Society of Japan, 2005
Abstract In spinel (MgAl2O4), the strongest infrared band at 485 cm−1 shows less LO–TO splitting than the medium band at 670 cm−1. This unexpected relationship is explained in terms of the vibrational coupling of these TO modes. A new manner for evaluating the LO mode is proposed.
Isao Kanesaka, Yuichi Hayashi, Yoshiyuki Morioka   +2 more
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Comparative studies on structural and luminescent properties of Eu3+:MgAl2O4 and Eu3+/Na+:MgAl2O4 nanopowders and nanoceramics

Optical Materials, 2012
Abstract Transparent Eu3+ doped MgAl2O4 and Eu3+/Na+ co-doped MgAl2O4 nanoceramics have been obtained by a low-temperature high-pressure (LTHP) sintering process using crystalline powders prepared by sol–gel method. Structural properties have been studied by X-ray diffraction (XRD) and analyzed by Rietveld method.
R.J. Wiglusz, T. Grzyb, A. Lukowiak, P. Głuchowski, S. Lis, W. Strek   +5 more
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Magnesium Aluminum Spinel (MgAl2O4)

1997
Publisher Summary Magnesium aluminum spinel (MgAl2O4) is a face-centered cubic material, the prototype for the spinel structural family, which includes binary oxides, sulfides, and selenides. The space group is Fd3m, unit cell length is 0.8084 nm, and the unit cell has eight formula units.
WILLIAM J. TROPF, MICHAEL E. THOMAS
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Dielectric relaxation in LiNbO3–MgAl2O4 nanocomposite

Materials Letters, 2012
Abstract LiNbO 3 –MgAl 2 O 4 nanocomposite was synthesized by a modified sol–gel and long-time sintering process. X-ray diffraction patterns reveal the presence of a rhombohedral structure LiNbO 3 and a cubic structure MgAl 2 O 4 . The average grain sizes were calculated.
Yemei Han, Lingxia Li, Wangsuo Xia, Yueying Liu, Xiang Ren   +4 more
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