Vacancy contribution to the heat content in aluminium

Abstract

By means of a high precision microcalorimeter, the heat absorbed or released by a crystal due to either the formation or the annealing out of lattice vacancies is measured directly. The sample, initially in equilibrium at a temperature T ₁, is given a ΔT= ± 50°c and so assumes an equilibrium configuration characteristic of the new temperature T ₂. During this process, a quantity of heat is absorbed or evolved. Accurate evaluation of this heat, at several temperatures T ₁, provides useful data on the formation energy of a vacancy and on the concentration of vacancies. The method was applied to Al, yielding very encouraging results: the energy of formation was ϵ_F=0ċ70±0ċ03 ev and the vacancy concentration at the melting point was C _{v F} = (6±0ċ8)10⁻⁴.