Europhysics Industrial Workshop EIW-12
Industrial Applications of Positron Annihilation

J. Phys. IV France 05 (1995) C1-157-C1-161
DOI: 10.1051/jp4:1995118

Investigation of Defects and Atomic Ordering in Fe₇₂Al₂₈ by Positron Annihilation and Mössbauer Spectroscopy

Y. Jiraskova¹, O. Schneeweiss¹, M. Sob¹, I. Novotny², I. Prochazka², F. Becvar², B. Sedlak², F. Sebesta³ and M.J. Puska<sup>4

1</sup>  Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Zizkova 22, CZ-616 62 Brno, Czech Republic
²  Department of Low-Temperature Physics, Charles University, V Holesovickach 2, CZ-180 00 Praha 8, Czech Republic
³  Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University, Brehova 7, CZ-115 19 Praha, Czech Republic
⁴  Laboratory of Physics, Helsinki University of Technology, SF-02150 Espoo, Finland

Abstract
Iron aluminide Fe₇₂Al₂₈ was investigated in states with different defect concentrations using the positron annihilation lifetime and Mössbauer spectroscopy methods. The dominant component of 178-187 ps, obtained from positron lifetime spectra analysis, corresponds to a high density of vacancies. In the sample where high concentrations of vacancies or dislocations and vacancy clusters were found simultaneously, a second component with a lifetime of 335 ps appears. Mössbauer results show that in the alloy above the Fe₃Al stoichiometry concentration the vacancies prefer to occupy the sublattice in the DO₃ superstructure which is reserved for both iron and aluminium atoms. However, this conclusion could not be verified by comparison of theoretical and experimental values of positron lifetimes as the theoretically predicted positron lifetimes for all three types of vacancies are nearly the same.

© EDP Sciences 1995