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Abstract

The high-pressure phase behaviour of americium and curium dioxides has been investigated using diamond anvil cells and X-ray diffraction. Both materials show a phase transition from a cubic (Fm3m) structure to an orthorhombic structure (Pnma) at high pressures. The high-pressure orthorhombic phases remain stable up to almost 55 Gpa , the maximum pressure studied. The first-order transition in each material is accompanied by a significant (almost 10%) volume collapse. Upon release of the applied pressure, the high-pressure forms revert back to the original fluorite structures, but there is a hysteresis effect. From the compression behaviour of the initial fluorite phase, bulj moduli were calculated for each oxide, and the values were found to be comparable to those for several other f-element oxides. The discontinuous volume decrease observed during the phase transformations are considered as reflecting a kinetically "delayed" adjustment to a more stable structure, which has a smaller molecular volume, rather than reflecting a significant change in bonding. The pressure behaviour of these actinide oxides will be discussed and compared to that displayed by other f electron dioxides.

Additional information

Authors: DANCAUSSE J P, European Commission, Joint Research Centre, Institute for Transuranium Elements, Karlsruhe (DE);HEATHMAN S, European Commission, Joint Research Centre, Institute for Transuranium Elements, Karlsruhe (DE);BENEDICT U, European Commission, Joint Research Centre, Institute for Transuranium Elements, Karlsruhe (DE);HAIRE R G, Oak Ridge National Laboratory (US)
Bibliographic Reference: An oral report given at: Actinides 2001 International Conference. Organised by: Japan Atomic Energy Research Institute and Atomic Energy Society of Japan. Held in: Hayama (JP), 4-11 November 2001.
Record Number: 200214361 / Last updated on: 2002-02-15
Category: PUBLICATION
Original language: en
Available languages: en