Lattice thermal conductivities of RbBr, RbI, and RbCl from 80 to 400 K

Abstract

The thermal conductivities $\lambda$ of RbBr, RbI, and RbCl were measured over the temperature range from 80 to 400 K with minimum uncertainties of ±2.5% at 80 K. The data were corrected for photon radiation, but the correction uncertainties caused the over-all measurement uncertainties to increase with increasing $T$. The data disagree with results by Eucken and Kuhn by as much as a factor of 4 but the RbCl data agree well with more recent work by Rosenbaum et al. The data were compared to an approximate equation for three-phonon umklapp scattering involving only acoustic mode phonons. The deviation of experimental thermal resistance ${\lambda }^{-1\mathrm{}}$ values from calculated values increased smoothly with increasing mass ratio. The presence of four-phonon umklapp scattering processes in the rubidium halides cannot be excluded because of the high-temperature behavior of ${\lambda }^{-1\mathrm{}}$. Distinct slope changes in ${\lambda }^{-1\mathrm{}}$ near the Debye temperatures, similar to those which occur in Si and Th${\mathrm{O}}_2$, were not observed in any of the three compounds although the effect could have been masked by the large experimental uncertainties at high temperatures.