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

The thermal conductivities λ 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 λ^-1 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 λ^-1. Distinct slope changes in λ^-1 near the Debye temperatures, similar to those which occur in Si and ThO₂, were not observed in any of the three compounds although the effect could have been masked by the large experimental uncertainties at high temperatures.