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6 results on '"BALIC ZUNIC, T"'

4. Comparative compressibility and structural behavior of spinel MgAl2O4 at high pressures: The independency on the degree of cation order.

Author

Nestola, F., Ballaran, T. Boffa, Balic-Zunic, T., Princivalle, F., Secco, L., and Negro, A. Dal

Subjects
CRYSTALS, X-ray crystallography, OPTICAL diffraction, SPINEL, CATIONS, HIGH pressure (Science), MINERALOGY
Abstract

The equation of state and the crystal structure evolution with pressure were determined for two single crystals of pure natural MgAl2O4 spinels with different degrees of order. The two samples studied were cut from a larger single crystal and one of them was experimentally disordered at high temperature. The two crystals, showing an inversion parameter x of 0.27 and 0.15 at ambient conditions, were loaded together in a diamond anvil cell and their unit-cell edge was measured up to about 7.5 GPa at 14 different pressures. The unit-cell volume, V0, the bulk modulus, KT0, and its first pressure derivative, K', were simultaneously refined using a third-order Birch-Murnaghan equation of state, giving the following coefficients: V0 = 529.32(2) ų, KT0 = 193(1) GPa, K' = 5.6(3) for the ordered sample and V0 = 528.39(2) ų, KT0 = 192(1) GPa, K' = 5.4(3) for the disordered one. Complete intensity data were collected at 0, 0.44, 2.92, 7.34, and 8.03 GPa in a separate experiment. For the ordered and disordered samples the oxygen atomic coordinate u remains practically unchanged inside the investigated pressure range with an average value of 0.2633(5) and 0.2614(2), respectively. As a consequence, the polyhedral compressibilities are similar and are not influenced by the Mg/Al distribution over the two crystallographic sites. This also suggests that pressure has little or no influence on the degree of order in the MgAl2O4 spinel. [ABSTRACT FROM AUTHOR]

Published
2007
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5. High-pressure crystal structure investigation of synthetic Fe2SiO4 spinel

Author

Monika Koch-Müller, Francesco Princivalle, Tonči Balić-Žunić, L. Secco, A. Dal Negro, Filippo Parisi, Fabrizio Nestola, Nestola, F, Balic-Zunic, T, Koch-Mueller, M, Secco, L, Princivalle, F, Parisi, F, Dal Negro, A, Nestola, F., Balic Zunic, T., Koch Muller, M., Secco, L., Princivalle, Francesco, Parisi, Filippo, and Dal Negro, A.

Subjects
Materials science, high pressure, X-ray diffraction, single crystal, synthetic Fe2SiO4 spinel, 010504 meteorology & atmospheric sciences, high pressure, X-ray diffraction, single crystal, synthetic Fe2SiO4 spinel, X ray diffraction, Spinel, 550 - Earth sciences, Crystal structure, engineering.material, 01 natural sciences, Crystallography, Ringwoodite, Octahedron, Geochemistry and Petrology, X-ray crystallography, engineering, Tetrahedron, Single crystal, 0105 earth and related environmental sciences, Solid solution
Abstract

The crystal structure of Fe2SiO4 spinel at room temperature was investigated at seven different pressures by X-ray diffraction, using a diamond anvil cell to examine the influence of Fe substitution on ringwoodite behaviour at high pressure. The results compared with those of a pure Mg endmember show that the substitution of Fe into the spinel structure causes only small changes in the compression rate of coordination polyhedra and the distortion of the octahedron. The data show that the compression rate for the octahedron and tetrahedron in (Mg,Fe)2SiO4 can be considered statistically equal for FeO6 and MgO6, as well as for SiO4 in both the endmembers. This shows why almost identical bulk moduli are reported along the solid solution in recent literature.

Published
2011

6. Comparative compressibility and structural behavior of spinel MgAl2O4 at high pressures: The independency on the degree of cation order

Author

Francesco Princivalle, Fabrizio Nestola, A. Dal Negro, L. Secco, T. Boffa Ballaran, Tonci Balic-Zunic, Nestola, F, BOFFA BALLARAN, T, BALIC ZUNIC, T, Princivalle, Francesco, and Secco, L. AND DAL NEGRO A.

Subjects
Bulk modulus, spinel, Spinel, Analytical chemistry, chemistry.chemical_element, X-ray single-crystal diffraction, cation ordering, high pressure, Crystal structure, engineering.material, Oxygen, Pressure range, Crystallography, Geophysics, chemistry, Geochemistry and Petrology, engineering, Compressibility, X ray single crystal diffraction, cataion ordering, Pressure derivative, Single crystal
Abstract

The equation of state and the crystal structure evolution with pressure were determined for two single crystals of pure natural MgAl 2 O 4 spinels with different degrees of order. The two samples studied were cut from a larger single crystal and one of them was experimentally disordered at high temperature. The two crystals, showing an inversion parameter x of 0.27 and 0.15 at ambient conditions, were loaded together in a diamond anvil cell and their unit-cell edge was measured up to about 7.5 GPa at 14 different pressures. The unit-cell volume, V 0 , the bulk modulus, K T0 , and its first pressure derivative, K ′, were simultaneously refined using a third-order Birch-Murnaghan equation of state, giving the following coefficients: V 0 = 529.32(2) A 3 , K T0 = 193(1) GPa, K ′ = 5.6(3) for the ordered sample and V 0 = 528.39(2) A 3 , K T0 = 192(1) GPa, K ′ = 5.4(3) for the disordered one. Complete intensity data were collected at 0, 0.44, 2.92, 7.34, and 8.03 GPa in a separate experiment. For the ordered and disordered samples the oxygen atomic coordinate u remains practically unchanged inside the investigated pressure range with an average value of 0.2633(5) and 0.2614(2), respectively. As a consequence, the polyhedral compressibilities are similar and are not influenced by the Mg/Al distribution over the two crystallographic sites. This also suggests that pressure has little or no influence on the degree of order in the MgAl 2 O 4 spinel.

Published
2007

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