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Title: High-pressure structural studies of strontium
Author: Bovornratanaraks, Thiti
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2001
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Previous structural work has shown that strontium undergoes a sequence of phase transitions up to 46 GPa. The relatively complex structures of Sr-IV and Sr-V, stable above 35 GPa and 46 GPa respectively, could not be solved and doubts remained about the correct assignment of the Sr-III structure. It is only comparatively recently, however, that experimental techniques have been developed to allow the detailed structural characterisation of these phases. To resolve these remaining uncertainties, the author has carried out a re-examination of the high-pressure structures and transitions in strontium using angle-dispersive powder-diffraction techniques with the image-phase area detector on station 9.1 at the SRS Daresbury Laboratory. The experimental set up has been improved so that data of sufficient quality could be obtained to allow the structures of these high pressure phases to be both correctly identified and accurately refined. The previously reported structure of Sr-III was found to be wrongly identified as having an orthorhombic Imma symmetry (with a structure similar to that of Si-III) and this has now been correctly identified as having the archetypal b-tin (I41 /amd) structure. The higher pressure phase of Sr, Sr-IV, has also been solved and the structure solution showed that it has a very complex monoclinic structure. This is the first time that this complex monoclinic structure has been reported in an element. Finally, the crystal structure of Sr-V has also been closely studied in comparison with the recently reported Ba-IV structure - based on the similarity of the diffraction patterns observed. The Sr-V structure is indeed found to be essentially the same as that of Ba-IV and it also has an intra-phase structural transition similar to those observed in Ba-IV.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available