Mössbauer studies of stable interstitial and substitutional sites of cobalt in gold

Author

Charles Freeland Steen, Portland State University

Sponsor

Portland State University. Department of Physics

First Advisor

Donald G. Howard

Date of Publication

1971

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Physics

Language

English

Subjects

Gold, Mössbauer effect

DOI

10.15760/etd.1916

Physical Description

1 online resource (76 pages)

Abstract

Precision measurements of the Debye-Waller factor of Fe⁵⁷ in Au using the wide black absorber technique have been made in the temperature range from room temperature to 830 K. The major source of error arises from Au L_y x-rays which are unresolved by the radiation detection system from the 14.4 KeV gamma ray. The K absorption edge of Br has been used to correct for the presence of x-rays.

These measurements have revealed the existence of two nonequivalent lattice sites which the Co⁵⁷ impurity (parent of Fe⁵⁷) may occupy. One of the sites has been populated by quenching the source from temperatures greater than 1150 K and has been identified as a substitutional lattice site. From an analysis of the Mössbauer spectrum it is concluded that some of the substitutional sites may be in the vicinity of dislocations. It has been determined that the impurity-host force constant for Fe⁵⁷ atoms in the substitutional site is about the same as the host-host force constant; the experimental value of the anharmonicity parameter ɛ (-2) for Fe⁵⁷ in the Au is nearly the same as calculated values of ɛ (-2) for pure Au.

The second site forms very slowly upon annealing the source at intermediate temperatures and has been identified as being interstitial in character. The slow rate of formation of the interstitial site indicates that diffusion is a primary mechanism in its formation. The second site must therefore be more complicated than an ordinary interstitial. It is proposed that this site is a split, or dumbbell, interstitial formed by substituting two impurity atoms for one of the Au atoms.

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Persistent Identifier

http://archives.pdx.edu/ds/psu/12394

Recommended Citation

Steen, Charles Freeland, "Mössbauer studies of stable interstitial and substitutional sites of cobalt in gold" (1971). Dissertations and Theses. Paper 1917.
https://doi.org/10.15760/etd.1916