Structural Studies of Europium at High Pressure
- Event time: 1:00pm
- Event date: 14th January 2013
- Speaker: Rachel Husband (Formerly School of Physics & Astronomy, University of Edinburgh)
- Location: Room 2511, James Clerk Maxwell Building (JCMB) James Clerk Maxwell Building Peter Guthrie Tait Road Edinburgh EH9 3FD GB
Unlike the majority of the lanthanide series, which are trivalent at ambient conditions, europium (Eu) is divalent due to its half-filled 4f7 electron shell. Eu also has a significantly larger atomic volume, and compressibility, than would be expected to be consistent with the general trend observed within the lanthanide series. Although the structures adopted below 18 GPa are well known, previous studies have found that the diffraction pattern of Eu becomes much more complex at 18 GPa. We have performed high-resolution angle-dispersive powder x-ray diffraction experiments on Eu up to a pressure of 50 GPa. We have found that the previously reported transition at 18 GPa was in fact due to pressure-induced changes in a contaminant phase, and not due to a transition in Eu itself. The presence of contamination peaks greatly complicated initial diffraction studies, and for this reason the structural behaviour of Eu above 18 GPa remained unknown until recently. We found that when great care was taken to minimize any sources of contamination, we were able to obtain clean samples. This enabled us to solve the structures of Eu-IV and Eu-V, which are stable between 31.5-38 GPa and 38-50 GPa, respectively. Both Eu-IV and Eu-V are complex incommensurate structures, the first of this kind to be observed in the lanthanide series.
This is a weekly series of informal talks given primarily by members of the soft condensed matter and statistical mechanics groups, but is also open to members of other groups and external visitors. The aim of the series is to promote discussion and learning of various topics at a level suitable to the broad background of the group. Everyone is welcome to attend..