The peculiarities of heat transfer in CO2 and N2O solids at low temperatures

Abstract

The thermal conductivities of CO 2 and N 2 O solids have been investigated in the low-temperature range 1-40 K. The thermal conductivities of CO 2 and N 2 O are large compared with those of simple molecular crystals such as N 2 , CO, or O 2 in the whole investigated temperature range. Analysis of the experimental data by the Callaway method shows that relatively large size of crystalline grains, low density of dislocations and weak phonon-phonon interaction might be the reasons for the good thermal conduction in these crystals at temperatures near the maxima. A comparison between calculated values of the intensity of normal phonon scattering processes and experiment gives evidence that in N 2 O there is an additional (in comparison with CO 2 ) giant scattering of phonons. This scattering is described in the frameworks of soft potential model by the resonance phonon scattering on tunnel states and low-energy vibratons.PACS: 63.20.-e Phonons in crystal lattices; 66.70.+f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves; 44.10.+i Heat conduction.