DENSITY VARIATION OF MOLTEN SILICON MEASURED BY AN IMPROVED ARCHIMEDEAN METHOD

The temperature dependence of the density of molten silicon was determined in the range from about 1,420-degrees-C to 1,650-degrees-C using a technique for accurate Archimedian density measurement. The temperature range was found to be divided into three regions in terms of the temperature coefficient of the density. An anomalous value in the thermal volume expansion coefficient of about 7.6 x 10(-4)-degrees-C-1 was observed just above the melting point. A thermal volume expansion coefficient of about 1.0 x 10(-4)-degrees-C-1 was obtained for the range from about 1,430-degrees-C to 1,540-degrees-C. Scattering of the density data was observed for temperatures higher than 1,540-degrees-C, for which the thermal volume expansion coefficient was estimated to be about 2.8 x 10(-4)-degrees-C-1. The time dependence of the density of molten silicon has also been examined. It was found to clearly increase for few hours after completion of melting, reaching a maximum, and thereafter decrease slowly.