Effects of Pressure, Temperature, and Defect Concentration on Positron Behavior in Metals
Positron lifetime distributions and the angular correlation of annihilation radiation are being used by numerous investigators to determine vacancy formation enthalpies and to reveal the presence of defects which may be precursors of voids in irradiated materials. However, the analysis that is needed to find vacancy formation energies is complicated by the presence of vacancy-independent temperature effects. These effects may be isolated by the application of sufficient pressure to remove the volume changes that result from increasing the temperature. For example, we find that the positron mean lifetime in cadmium at 296 K and 9.8 kb is 178 ± 2 ps, significantly larger than the lifetime of 170 ± 2 ps observed at 77 K and 0 kb, even though the volume of the sample is smaller in the former case, demonstrating that the effect of temperature is more than that of a simple volume change.
KeywordsAngular Correlation Vacancy Formation Positron Lifetime Annihilation Radiation Positron Lifetime Spectrum
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