Thermal conductivity of the Ihand XI phases of ice

The thermal conductivity {λ} of KOH-doped ice was measured using the transient hot-wire method at temperatures in the range 55--250 K and at pressures up to 0.15 GPa. With an isobaric increase of temperature at 0.08 GPa, {λ} decreased 17% at about 74 K. This decrease is associated with the known transition from ordered phase XI to phase Ih which exhibits orientational disorder of H₂O. A model for {λ} indicates that the decrease of {λ} at the transition is due to an increase of the lattice anharmonicity which might be caused by the disorder in phase Ih. It was inferred from the temperature dependence of {λ} that phonon scattering in both phases Ih and XI is dominated by three phonon umklapp processes. At 58 K, {λ} of supercooled phase Ih decreased slightly with increasing pressure whereas {λ} of phase XI was independent of pressure.