The large concentration fluctuations in the liquid eutectic systems with deep eutectic points

摘要

The electrical resistivity, rho, was investigated from 1373 K to the melting temperature for liquid Au-Ge and Ag-Ge alloys, having eutectic temperatures that are far lower than the melting temperatures of the respective constituent metals ('deep eutectic point'). Positive departures from the extrapolated linear temperature dependence of rho in the high temperature range were found in the homogeneous liquid phases near the eutectic point. As a result, the temperature coefficient of the electrical resistivity, drho/dT, shows a minimum near the eutectic composition. Particularly, the positive deviation of rho for the eutectic composition is extremely large for liquid Au-Ge alloys in the wide temperature range, 634-1200 K, and drho/dT shows a negative value below 800 K, though rho itself remains metallic in character. These results are analyzed from the point of view of the existence of concentration fluctuations. The volume fraction of concentration fluctuation is qualitatively evaluated and compared with other systems that were found recently to show a similar behavior. (C) 2002 Elsevier Science B.V. All rights reserved. [References: 5]