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Stochastic Vacancy Motion in B2 Intermetallics Detected by PAC

Published online by Cambridge University Press:  10 February 2011

Bin Bai ,
Gary S. Collins ,
Harmen Thys Nieuwenhuis ,
Mingzhong Wei  and
William E. Evenson
Bin Bai
Affiliation:
Department of Physics, Washington State University, Pullman, WA
Gary S. Collins
Affiliation:
Department of Physics, Washington State University, Pullman, WA, [email protected].
Harmen Thys Nieuwenhuis
Affiliation:
Department of Physics, Washington State University, Pullman, WA
Mingzhong Wei
Affiliation:
Department of Physics, Washington State University, Pullman, WA, [email protected].
William E. Evenson
Affiliation:
Department of Physics, Brigham Young University, Provo, UT
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Abstract

Using perturbed angular correlation of gamma rays (PAC), nuclear relaxation has been detected at high temperature in highly ordered B2 intermetallics that is attributed to stochastic motion of vacancies near 111In/Cd probe atoms. The relaxation is of quadrupole interaction signals due to transition-metal vacancies in the first atomic shells of the probes. Possible relaxation mechanisms are reorientation of the vacancy with respect to the probe, detrapping of the vacancy, or trapping of a second vacancy. The relaxation reaches values of 10 MHz at temperatures of 1500K, 1200 K and 1170 K, respectively, for NiAI, FeAl and PdIn. For NiAl and FeAI, the onset of relaxation is abrupt, suggesting an activation enthalpy for the associated vacancy motion of several electron-volts. For PdIn, the relaxation has an activation enthalpy of 1.00(19) eV, a value significantly lower than might be expected naively on the basis of diffusion data. This difference gives insight into vacancy motion and diffusion mechanisms in PdIn.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 527: Symposium Z – Diffusion Mechanisms in Crystalline Materials , 1998 , 209
Copyright
Copyright © Materials Research Society 1998

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References

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