Lattice Thermal Conductivity of Solid Helium. II. Isotopic Mixtures

We have analyzed the thermal-conductivity data of He⁴-rich isotopic mixtures of solid helium in the hcp phase and He³-rich mixtures in the bcc phase at the molar volume 20.2 cm³/mole measured by Bertman et al. It is found that the T³ dependence of normal processes generally used in Callaway's model can explain the thermal-conductivity data in the temperature range 0.6 to 1.8^∘{}K. The concentration dependence of the lattice distortion scattering due to added isotopic impurity is seen to be the theoretically expected one, i.e., x(1-x), and the stronger concentration dependence noticed by Bertman is not observed.