Quenching and Annealing of Lattice Vacancies in Pure Silver

Abstract

Quenching and annealing experiments on 99.998% pure silver lead to the following results: The energy required to form a lattice vacancy is 1.10\ifmmode\pm\else\textpm\fi{}0.04 eV. The activation energy required to move a lattice vacancy is 0.83\ifmmode\pm\else\textpm\fi{}0.05 eV. In specimens quenched from above 600\ifmmode^\circ\else\textdegree\fi{}C most of the defects observed annealed with an activation energy of 0.57\ifmmode\pm\else\textpm\fi{}0.03 eV. Pulse heating breaks up the 0.57-eV defect; at least one of the fragments thus produced is a single vacancy having migration energy 0.83\ifmmode\pm\else\textpm\fi{}0.05 eV. It is suggested that the 0.57-eV defect is a divacancy. The pulse heating establishes the binding energy of the 0.57-eV defect to be 0.38\ifmmode\pm\else\textpm\fi{}0.05 ev. Upon annealing a quenched specimen below 0\ifmmode^\circ\else\textdegree\fi{}C the 0.57-eV defect anneals by second-order kinetics. Upon annealing a quenched specimen above 90\ifmmode^\circ\else\textdegree\fi{}C one observes a fast annealing (approximately first order with energy of motion 0.60\ifmmode\pm\else\textpm\fi{}0.06 eV) followed by a slow annealing process having energy of motion 0.80\ifmmode\pm\else\textpm\fi{}0.1 eV. It is suggested that above 90\ifmmode^\circ\else\textdegree\fi{}C the 0.57-eV defect does not cluster, but migrates to dislocations. The fact that below 0\ifmmode^\circ\else\textdegree\fi{}C the 0.57-eV defect forms clusters, whereas above 90\ifmmode^\circ\else\textdegree\fi{}C it does not, leads to a binding energy for quadrivacancies of 0.30\ifmmode\pm\else\textpm\fi{}0.08 eV.