Thermal conductivity of mica at low temperatures

The thermal conductivity of muscovite and phlogopite has been measured over a temperature range of 3 to 320 K, in directions parallel and perpendicular to the cleavage planes. Both materials showed anisotropic behaviour. The room temperature values for muscovite and phlogopite, respectively, were 4.05 and 3.7 W m^–1 K^–1 for conductivity parallel to the planes, and 0.46 and 0.44 W m^–1 K^–1 perpendicular to the planes. Plots of the variation of thermal conductivity with temperature for both directions in the two materials show a gradual rise in conductivity as the temperature is lowered below room temperature. All four curves reach a peak at about the same temperature of 15 K. The peak values obtained were 12.4 and 7.25 W m^–1 K^–1 parallel to the planes, and 4.7 and 2.05 W m^–1 K^–1 perpendicular to the planes.On leave from Australian Broadcasting Commission.