Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Structure and Stability of Bi1-xSbx and CaAl2-xZnx
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is focused on two intermetallic systems Bi1-xSbx and CaAl2-xZnx. Bi and Sb transform into a peculiar incommensurate composite structure under pressure and our intention was to examine the structure and how alloying influences this incommensurate structure. Our investigation was obscured by the occurrence of a phase separation, which accompanied the transition A7 → Bi III. Most remarkable is the finding that structural parameters of phases with the Bi III composite structure were observed to be almost unaffected by pressure and composition effects.

Secondly, phase and structural stability relations within the AB2 pseudo-binary system CaAl2-xZnx was studied. In CaAl2-xZnx, the C36-type Laves phase was observed for the first time, but not the C14-type, and a VEC induced structural transition C15-type → C36-type takes place with increasing x. The exchange of Al by Zn decreases the size of the B-type atom network surrounding Ca and at concentrations x > 0.95, the Laves phase structure is succeeded by the CeCu2 type structure, which tolerates a larger size ratio A/B. The C15-type → C36-type transformation in the CaAl2-xZnx system is induced by the valence electron concentration VEC.

Through the analysis of MEM/Rietveld from synchrotron powder X-ray diffraction data, the total charge distributions and deformation charge densities were obtained for cubic and 4H hexagonal Laves phases in CaAl2-xZnx and also for orthorhombic CaZn2. The overlap electrons, which take an important role in stabilising the crystal structures, are clearly observed in the Kagome-net between B-net atoms. The Ca atoms are located in the space formed by the B-net atoms.

From the high-pressure experiments it was concluded that at elevated temperatures, 1000-1500 °C, the hexagonal C36 structure type transforms to the C15 structure type between 6.2 and 9.4 GPa, and the orthorhombic CeCu2 phase to a hexagonal Laves phase between 7.5 and 15.5 GPa.

Place, publisher, year, edition, pages
Stockholm: Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi , 2005. , 86 p.
National Category
Inorganic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-624ISBN: 91-7155-109-3 (print)OAI: oai:DiVA.org:su-624DiVA: diva2:196232
Public defence
2005-09-19, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 13:00
Opponent
Supervisors
Available from: 2005-08-27 Created: 2005-08-27 Last updated: 2011-03-10Bibliographically approved
List of papers
1. Comparative Study of the High-Pressure Behaviour of As, Sb, and Bi
Open this publication in new window or tab >>Comparative Study of the High-Pressure Behaviour of As, Sb, and Bi
2002 In: Journal of the American Chemical Society, ISSN 1520-5126, Vol. 124, 15359-15367 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-23985 (URN)
Note
Part of urn:nbn:se:su:diva-624Available from: 2005-08-27 Created: 2005-08-27Bibliographically approved
2. Alloys Bi1-xSbx under High-Pressure
Open this publication in new window or tab >>Alloys Bi1-xSbx under High-Pressure
Show others...
2004 In: Physical Review B, ISSN 1098-0121, Vol. 69, 134203-1 - 134203-10 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-23986 (URN)
Note
Part of urn:nbn:se:su:diva-624Available from: 2005-08-27 Created: 2005-08-27Bibliographically approved
3. Crystal Structures and their Stabilities in CaAl2-xZnx Phases
Open this publication in new window or tab >>Crystal Structures and their Stabilities in CaAl2-xZnx Phases
Show others...
Manuscript (Other academic)
Identifiers
urn:nbn:se:su:diva-23987 (URN)
Note
Part of urn:nbn:se:su:diva-624Available from: 2005-08-27 Created: 2005-08-27 Last updated: 2010-01-13Bibliographically approved
4. Electron charge distribution of CaAl2−xZnx: Maximum Entropy Method combined with Rietveld analysis of High-resolution-synchrotron X-ray powder diffraction data
Open this publication in new window or tab >>Electron charge distribution of CaAl2−xZnx: Maximum Entropy Method combined with Rietveld analysis of High-resolution-synchrotron X-ray powder diffraction data
Show others...
2008 (English)In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 181, no 8, 1998-2005 p.Article in journal (Refereed) Published
Abstract [en]

Using short wavelength X-rays from synchrotron radiation (SPring-8), high-resolution powder diffraction patterns were collected. In order to study both the structural relationship and the mechanism of stability in the CaAl2−xZnx system, among the Laves phases (MgCu2 and MgNi2 type) and KHg2-type structures, the charge density distribution of CaAl2−xZnx as a function of x was obtained from the diffraction data by Rietveld analysis combined with the maximum entropy method (MEM). In the MEM charge density maps overlapping electron densities were clearly observed, especially in the Kagomé nets of the Laves phases. In order to clarify the charge redistribution in the system, the deformation charge densities from the densities formed by the constituent free atoms are discussed. In the ternary MgNi2-type phase, partial ordering of Al and Zn atoms is observed, a finding that is supported by ab-initio total energy calculations.

Keyword
Intermetallic compounds, Laves phases, Charge density, Maximum entropy method
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:su:diva-24698 (URN)10.1016/j.jssc.2008.04.034 (DOI)000259098000041 ()
Available from: 2008-02-25 Created: 2008-02-12 Last updated: 2011-03-10Bibliographically approved
5. Beyond the Traditional AB2 Laves Phase: Transmission Electron Microscopy Study
Open this publication in new window or tab >>Beyond the Traditional AB2 Laves Phase: Transmission Electron Microscopy Study
Show others...
Manuscript (Other academic)
Identifiers
urn:nbn:se:su:diva-23989 (URN)
Note
Part of urn:nbn:se:su:diva-624Available from: 2005-08-27 Created: 2005-08-27 Last updated: 2010-01-13Bibliographically approved

Open Access in DiVA

No full text

By organisation
Department of Physical, Inorganic and Structural Chemistry
Inorganic Chemistry

Search outside of DiVA

GoogleGoogle Scholar

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 278 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf