Thermal Diffusivity of Crystalline and Liquid Silicon and an Anomaly at Melting

The thermal diffusivity of Si was measured by a laser flash method up to 1723 K. SiC and fused quartz cells were prepared for the measurement on the melt. The thermal conductivities of the crystal and the melt at the melting point were determined to be 27.3±0.3 and 56±1 W/mK, respectively. It is suggested that a new (metastable) phase exists in a narrow temperature range just above the melting point. It irreversibly transformed to ordinary liquid metal. The new phase may have very low emissivity, and/or large specific heat.