Thermal conductivity of single-crystals isotopically enriched $^{70}$Ge, $^{72}$Ge, $^{74}$Ge in the temperature range of 80–310 K

The temperature dependence of the thermal conductivity $\kappa(T)$ of single crystals isotopically enriched $^{70}$Ge (99.926%), $^{72}$Ge (99.980%), $^{74}$Ge (99.921%) has been measured in the temperature range 80–310 K. In the studied temperature range, the thermal conductivity is determined by anharmonic processes of phonon scattering; a decrease in the thermal conductivity with increasing mass of the germanium isotope is experimentally observed.