Deviation from Wiedemann–Franz Law for the Thermal Conductivity of Liquid Tin and Lead at Elevated Temperature

The thermal conductivities of tin and lead in solid and liquid states have been determined using a nonstationary hot wire method. Measurements on tin and lead were carried out over temperature ranges of 293 to 1473 Kand 293 to 1373 K, respectively. The thermal conductivity of solid tin is 63.9±1.3 W·m−1 ·K−1 at 293 K and decreases with an increase in temperature, with a value of 56.6±0.9 W·m−1 ·K−1 at 473 K. For solid lead, the thermal conductivity is 36.1±0.6 W·m−1 ·K−1 at 293 K, decreases with an increase in temperature, and has a value of 29.1±1.1 W·m−1 ·K−1 at 573 K. The temperature dependences for solid tin and lead are in good agreement with those estimated from the Wiedemann–Franz law using electrical conductivity values. The thermal conductivities of liquid tin displayed a value of 25.7±1.0 W·m−1 ·K−1 at 573 K, and then increased, showing a maximum value of about 30.1 W·m−1 ·K−1 at 673 K. Subsequently, the thermal conductivities gradually decreased with increasing temperature and the thermal conductivity was 10.1±1.0 W·m−1 ·K−1 at 1473 K. In the case of liquid lead, the same tendency, as was the case of tin, was observed. The thermal conductivities of liquid lead displayed a value of 15.4± 1.2 W·m−1 ·K−1 at 673 K, with a maximum value of about 15.6 W·m−1 ·K−1 at 773 K and a minimum value of about 11.4±0.6 W·m−1 ·K−1 at 1373 K. The temperature dependence of thermal conductivity values in both liquids is discussed from the viewpoint of the Wiedemann–Franz law. The thermal conductivities for Group 14 elements at each temperature were compared.