Thermal Conductivity in Sodium Chloride Crystals Containing Silver Colloids

Measurements are presented of the low-temperature thermal conductivity of crystals of sodium chloride containing colloidal particles of silver. It is found that parts per million of colloidal material can substantially reduce thermal conductivity in the temperature range below the peak conductivity. Comparison is made with crystals containing the same concentrations of unprecipitated silver chloride, and with pure crystals. In addition, the scattering of phonons at external crystal surfaces is discussed.