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Pressure Induced Phase Transitions and EOS Derived for Laves Phase Deuterides ErFe2Dx (x = 1.35, 1.9 and 3.4)

Sugiura H., Filipek S. M., Paul-Boncour V., Marchuk I.

Polish Journal of Chemistry

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2008

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Vol. 82, nr 10

1959-1972

EN

The energy dispersive X-ray diffraction patterns of ErFe2Dx deuterides [where x = 1.35 (alfa1 phase), x = 1.9 (alfa2 phase) and x = 3.4 (beta phase)] have been measured under pressure up to 31 GPa. Compression curves and equation of state (EOS) parameters were determined us ing ex per i men tal data. ErFe2D1.35 and ErFe2D1.9 de com posed into phases with low (alfa1 ,, alfa 2 ,) and high (alfa1 ,, alfa 2 ,,) deuterium concentrations around 8 GPa. As the pressure was raised above 8 GPa, the D con cen tra tion in the alfa1 ,, alfa 2 , phases re mained close to about x = 0.2 whereas in the alfa1 " alfa 2 ,, phases it in creased from x = 2.1 to a max i mum of x = 4.6 at about 20 GPa. This was accompanied with a progres sive distortion of the alfa1 ,, alfa 2 ,, phases from a cubic to wards an orthorhombic structure. This decomposi tion process occurs with a large hysteresis effect between loading and unloading cycles. A similar decomposition into beta , and beta ,, phases seem ingly oc curs also for ErFe2D3.4 at 11 GPa being accompanied with a change of initial rhombohedral (R3m) symmetry to another one. The D content in this new beta" phase (x ~4.6) be comes close to that of orthorhombic ErFe2H5. These processes have character of spinodal decomposition and are related to a lowering of its critical temperature upon applied pressure.

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High pressures studies on hydrides of selected manganese alloys

Sugiura H., Filipek S., Paul-Boncour V., Marchuk I., Liu R., Pyun S.

Nukleonika

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2006

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Vol. 51,suppl.1

73-77

EN

Specific behavior found in hydrides formed in manganese, Mn-Ni and YMn2 under high pressure is presented and discussed. The synthesis of ferromagnetic fcc-manganese was proved. Parameters of the equations of state (EOS) derived from measurements in the diamond anvil cell (DAC) are summarized for manganese hydrides and for hydrides derived from YMn2 Laves phase. It was found that the compression behavior of recently discovered YMn2H6 is different from YMn2-based hydrides with lower hydrogen content.

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Investigation of ZrFe2 and ZrCo2 Under Very High Pressure of Gaseous Hydrogen and Deuterium

Filipek S. M., Jacob I., Paul-Boncour V., Percheron-Guegan A., Marchuk I., Mogilyanski D., Pielaszek J.

Polish Journal of Chemistry

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2001

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Vol. 75, nr 12

1921-1926

EN

New hydrides and deuterides of Laves cubic phases ZrFe2 and ZrCo2 were synthesized by high hydrogen (deuterium) pressure technique. For both Laves phases the symmetry of lattice does not change but a large expansion of lattice parameter (by 8% for ZrFe2 and by 4.5% for ZrCo2) occurs during hydrides (deuterides) formation. In contrast to the rela-tively stable hydride (if stored in an inert atmosphere) formed in ZrFe2, the ZrCo2H2 de-composes easily at 25°C. Large lattice expansion of ZrFe2 during the deuteride formation changes only slightly its magnetic properties.