Defect recovery studied by positron lifetime measurements in quenched and electron irradiated dinickel silicide

A. Jennane1*, J. Bernardini2, G. Moya2

1 L.M.M, Faculté des Sciences et Techniques, Université Hassan 1er, B.P. 577, Settat, Morocco.

2 L2MP, UMR CNRS-6137, Faculté des Sciences St-Jérôme, Case 151,13397 Marseille Cedex 20, France.

* Corresponding author. E-mail : lmm.fsts@menara.ma ; adibjennane@yahoo.fr

Received : 28 October 2003; revised version accepted : 25 March 2005

Abstract

Specimens of Ni2Si intermetallic compound were studied by means of positron lifetime spectroscopy after electron irradiation at 20K. Isochronal spectra of the positron average lifetime were followed from low temperature to 750K. The results are in fair agreement with those obtained by Doppler broadening measurements. In irradiated samples interstitials migrate and recombine with immobile vacancies at a temperature as low as 77K. From 325K vacancies became mobile and lead to the formation of three-dimensional mixed clusters. At about 400K, the less stable clusters evaporate. The recovery is still incomplete at 700K. The positron lifetime variation as a function of measuring temperature made it possible to characterise the dimensional nature of the clusters formed during the annealing. At last present results are compared with previous ones obtained in pure nickel and Ni-Si (0.8 at%) solid solutions.

Keywords : Composé intermétallique ; Interstitiels ; Lacunes ; Amas ; Positons ; Temps de vie.

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