Thermal conductivity of some metals under pressure

University dissertation from Umeå : Umeå universitet

Abstract: Although measurements of a wide variety of physical properties have been carried out under pressure during the last decades, data for thermal conductivity under pressure are sparse. This is especially so in the case of metals, where the experimental difficulties are very large. In this work a new method to make such measurements is presented, together with experimental results for copper, silver, gold, and aluminium at room temperature and pressures up to 2.5 GPa.The first part of the work describes in some detail the method used.This method is a variation of the well known Ångström method. The measured property is thus not the thermal conductivity, but instead the thermal diffusivity. Both the Ångström method, and the variation of this used in this work, are described in detail. Several further simplifications of the method are also investigated. The experimental equipment is described in detail, as is also the construction of samples and pressure cells.After a description of the experimental procedure, experimental results are presented for the thermal diffusivity of the metals studied, at pressures up to 2.5 GPa. These data are converted to thermal conductivity data by the use of available data on density and specific heat capacity for these metals under pressure. In a few cases, theoretically calculated values for the latter quantity are used. After a brief look at the theory for the thermal conductivity of metals, the experimental results are compared to simple theoretical predictions. The agreement is found to be good. Contrary to theoretical predictions, however, the electronic Lorentz function is found to increase with increasing pressure for the noble metals.