Thermal conductivity of solid neon

The thermal conductivity of solid neon samples was measured from 0.5 to 10 K. An isotopically purified ²⁰Ne sample and a ²⁰Ne sample with 0.15-at.% ⁴He, as well as a sample with the natural isotopic mixture, were studied. Measurements were made at molar volumes between 13.4 and 12.89 cm³/mole. The conductivity is found to increase rapidly with decreasing molar volume. The conductivity is determined primarily by the intrinsic phonon scattering above about 4 K. Normal and Umklapp phonon scattering terms are found to be necessary to make reasonable fits to the data using the Callaway relaxation-rate theory. The functional form of the three-phonon Normal processes can be represented best by τN^-1∝BNx²T⁴ sec^-1, where x=ωkT, ω is the phonon frequency, and BN is a constant. These fits show that the enhancement of phonon scattering from isotopic defects due to differences in zero-point energy decreases with molar volume.