HIGH-PRESSURE OF SOLID NOBLE-GASES IN METALS

The fact that noble gas ions implanted in metals with concentrations of a few percent precipitate at room temperature as solid bubbles under high pressure with a structure epitaxial with the host matrix (fcc or hcp) has been investigated recently. A brief survey of the results measured by transmission electron microscopy, glancing angle X-ray diffraction, energy-loss spectroscopy and positron annihilation is given. The main part of this paper deals with a study on83Kr+ implanted in Al using Mössbauer spectroscopy. The results are as follows: the precipitates grow from 1.5 nm after implantation to 3.7 nm after 700 K annealing. The recoilless fractions can be fitted very well to a Debye model. On annealing. the characteristic Mössbauer temperature gradually decreases from 89 K to 64 K, the value for solid Kr at 1 bar. At the same time a decrease in the isomer shift is observed. Even after annealing at 700 K our experiments do not show melting in the temperature range 0-230 K. © 1990 J.C. Baltzer AG, Scientific Publishing Company.