LOW-TEMPERATURE THERMAL-CONDUCTIVITY OF TWINNED AND UNTWINNED INDIUM THALLIUM ALLOYS

The low-temperature lattice thermal conductivity of twinned and untwin ned, martensitic and non-martensitic, indium-thallium alloys has been measured to probe the effect of twin boundaries on phonon thermal tran sport. The phonon scattering by electrons, sample surfaces, dislocatio ns, and thallium ''impurities'' is accounted for adequately by existin g theoretical models. The reduced lattice thermal conductivity seen in twinned samples is attributed to additional phonon scattering by twin boundaries and, for the polycrystalline samples, by grain boundaries. Phonon scattering by twin boundaries is much weaker than that general ly reported for grain boundaries, and is well represented by an acoust ic-mismatch model.