Dissertation
Site Preference of Indium Solute Atoms in a Series of Cubic Laves RAl2 Phases
Washington State University
Doctor of Philosophy (PhD), Washington State University
2023
DOI:
https://doi.org/10.7273/000005375
Abstract
Site preferences of dilute indium impurity atoms were studied in seven cubic Laves phases RAl2 (R= La, Ce, Nd, Sm, Gd, Dy, Ho) having the cF24 (C15) structure. Preferences were measured in thermal equilibrium for temperatures in the range of 573 - 1073 K using perturbed angular correlation of gamma rays (PAC). From the temperature dependences of ratios of fractions of probes on R and Al sites, transfer-enthalpies of indium solutes between the two sublattices were determined. Transfer-enthalpies were found to vary linearly along the series as a function of lattice parameter, changing sign between LaAl2 and CeAl2. The ratio of site-fractions of probes on R and Al sites also changed along the series. For LaAl2, the Al site was preferred at low temperature, but for the other six RAl2 phases, the R site was preferred. Transfer-enthalpies were found to be correlated with site-fraction ratios at an intermediate temperature of the order 923 K. A model was developed based on the local geometry of atoms within the cF24 unit cell and the relative sizes of R, Al, and In atoms. The model takes into account charge-transfer between atoms owing to electronegativity differences and strain-energy concepts based on the semi-empirical Miedema model. The model successfully reproduced the linear variation in the transfer-enthalpies. Some experiments included samples with a two-phase mixture of RAl2 with either RAl3 or RAl. Dilute indium solutes were observed to preferentially occupy RAl3 phases over RAl2.
Metrics
3 File views/ downloads
30 Record Views
Details
- Title
- Site Preference of Indium Solute Atoms in a Series of Cubic Laves RAl2 Phases
- Creators
- Bryant Ward
- Contributors
- Gary S Collins (Advisor)Yi Gu (Committee Member)Nicholas Cerruti (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Physics and Astronomy, Department of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 103
- Identifiers
- 99901031138601842
- Language
- English
- Resource Type
- Dissertation