LXIX. The thermal and electrical conductivities of beryllium

Abstract

Several samples of metallic beryllium have been studied. Heat treatment to temperatures of the order of 700°c invariably caused increases in the thermal and electrical conductivities and determinations of these two properties have been made for both as received and heat treated states. For the most part the thermal conductivity measurements were limited to the range 50° to 350°c, but in one instance these measurements were extended to 700°c. The thermal conductivity is found to have a large negative temperature coefficient, in contrast to the only previous measurements recorded above room temperature which had yielded a positive temperature coefficient. Much of the abnormal nature of the temperature variation of the Lorenz function of beryllium which these results of Lewis (1929) had indicated now disappears. Analysis of the present results suggests that beryllium, on account of its high characteristic temperature, possesses a considerable lattice component of thermal conduction, K_a , which can be represented over the range 50° to 400°c by the equation where K_g is in joule cm/cm² see°c and T is in °k. The electronic component K_e is represented over the same range by the equation where ρ is the electrical resistivity in ohm cm²/cm. Hence the equation suggested ibr the derivation of the thermal conductivity of a sample of beryllium from a knowledge of its electrical resistivity is:— This equation fits the present results to within −6 to +5%, It could probably be applied to temperatures above 400°c, but, not below O°c, where further investigation is considered necessary.