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 eF=0⋅70±0⋅03 ev and the vacancy concentration at the melting point was C v F = (6±0⋅8)10−4.