Thermal formation of vacancies in Cu₃Sn

Abstract

The formation of thermal vacancies in Cu 3 Sn has been investigated by using positron annihilation lifetime spectroscopy. Positron lifetime measurement was performed in-situ between 293 K and 673 K. The positron lifetime below 433 K was found to be about 140 ps, which indicates that there are no detectable vacancies below 433 K. A sharp increase of the mean positron lifetime τ m , which is due to thermal vacancy formation, starts around 453 K and the saturation trapping of positrons by thermal vacancies are observed above 633 K. The Arrhenius plot of the positron trapping rate, which is proportional to the vacancy concentration, represents a linear behavior and the vacancy formation enthalpy was determined to be 0.63±0.02 eV. This value is relatively low comparing with that expected from the melting temperature (950 K) of this alloy.