DENSITY-MEASUREMENTS FOR LIQUID SE-TE MIXTURES AT HIGH-TEMPERATURES AND PRESSURES

Density measurements for liquid Se60Te40, Se80Te20 and Se90Te10 were carried out at temperatures up to 1600-degrees-C and pressures up to 800 bar. The measurements were performed by means of X-ray absorption using a high-pressure vessel and a sapphire cell of the authors' own design. A distinct density variation was observed for each mixture. The thermal expansion coefficient, alpha, becomes negative in a certain temperature region for liquid Se60Te40 and Se80Te20 when the semiconductor-metal transition occurs. For liquid Se90Te10, alpha remains positive in the low pressure region below about 600 bar, but a temperature range which results in negative a appears at higher pressures.