DENSITY VARIATION OF MOLTEN SILICON MEASURED BY AN IMPROVED ARCHIMEDEAN METHOD

The temperature dependence of the density of molten silicon was determ ined in the range from about 1,420-degrees-C to 1,650-degrees-C using a technique for accurate Archimedian density measurement. The temperat ure range was found to be divided into three regions in terms of the t emperature coefficient of the density. An anomalous value in the therm al volume expansion coefficient of about 7.6 x 10(-4)-degrees-C-1 was observed just above the melting point. A thermal volume expansion coef ficient of about 1.0 x 10(-4)-degrees-C-1 was obtained for the range f rom about 1,430-degrees-C to 1,540-degrees-C. Scattering of the densit y data was observed for temperatures higher than 1,540-degrees-C, for which the thermal volume expansion coefficient was estimated to be abo ut 2.8 x 10(-4)-degrees-C-1. The time dependence of the density of mol ten silicon has also been examined. It was found to clearly increase f or few hours after completion of melting, reaching a maximum, and ther eafter decrease slowly.