Jm. Clayton et al., DEFORMATION-INDUCED MICROVOIDS IN BISMUTH AND POSSIBLE POSITRONIUM FORMATION, Journal of physics. Condensed matter, 7(16), 1995, pp. 3181-3186
Positron annihilation spectroscopy is used to study the annealing stag
es in cold worked single and polycrystalline bismuth. A large drop (on
set similar to 240 K) is observed in the doppler-broadening lineshape
measurement, in agreement with previous work. Results of positron life
time experiments, conducted around the main annealing stage, suggest t
he formation of positronium at microvoids in cold worked Bi.