Dissertation
Solute-Solute Interactions in Intermetallic Compounds Studied Using Perturbed Angular Correlation of Gamma Rays
Doctor of Philosophy (PhD), Washington State University
01/2017
Handle:
https://hdl.handle.net/2376/12219
Abstract
Interactions between pairs of solute atoms dissolved in a binary intermetallic compound were studied. Perturbed angular correlation of gamma rays (PAC) was used to detect solute atoms next to impurity PAC probe atoms in GdAl2 through measurements of nuclear quadrupole interactions. Interaction enthalpies between 111In probe atoms and 1 at.% of Ag, Cu, Au, or natural In solutes were measured and found to be in the range ±0.20 eV, similar to values observed in studies of solute pairs in pure metals by Krzysztof Królas et al. in the 1980s. Some expected solute pairs were not observed, presumably because their nuclear quadrupole interactions could not be resolved from other signals. Results for Ag-doped GdAl2 which previously appeared in Hyperfine Interactions 238:18 (2017) (Appendix A), have been updated with an improved analysis methodology, but without major changes in deduced interaction enthalpies. New results are presented for In, Cu, and Au solutes.
A previous study of undoped GdAl2 (Phys. Rev. B69, 174202 (2004)) showed that dilute 111In probes transfer from the Gd- to Al-sublattice with increasing temperature, with an activation enthalpy of 0.343(7) eV. This is a two-level system reflecting the enthalpies of the probe atom on the two sublattices. 1 at.% of In, Ag, Au, or Cu solute was found to reduce the transfer enthalpy to zero. This implies that solute atoms compete with 111In to transfer to the Al-sublattice, effectively decreasing the degeneracies of sites available to probe atoms on the Al-sublattice. Further measurements showed that 0.4 at.% In solute was sufficient to reduce the transfer enthalpy to zero. The degeneracies appear correlated with the width of the GdAl2 phase field and solute mole fraction, suggesting that the phase boundary compositions of GdAl2 are at 33.3 at.% Gd and ~32 at.% Gd.
A previous study described segregation of 111In probes to interphase boundaries in GdNi2. New analysis suggests that Cu-solutes cluster near 111In probe atoms in that phase. Experiments underway to combine diffusion measurements of Cd-tracer atoms and PAC measurements of jump frequencies in Al3Er to determine the correlation coefficient for impurity diffusion are outlined.
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Details
- Title
- Solute-Solute Interactions in Intermetallic Compounds Studied Using Perturbed Angular Correlation of Gamma Rays
- Creators
- Ryan Murray
- Contributors
- Gary S Collins (Advisor)Matthew D McCluskey (Committee Member)Kelvin G Lynn (Committee Member)Matthew O Zacate (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Department of Physics and Astronomy; National Science Foundation, Metals and Nanostructures Program
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 185
- Identifiers
- 99900581516101842
- Language
- English
- Resource Type
- Dissertation