Thermodynamics of liquid-liquid crossover transition in liquid Si15Te85eutectic alloy

M Narita,Y Tsuchiya,I Konishi

doi:10.1051/epjconf/20111501021

Abstract

Specific heat of liquid Si 15 Te 85 was measured using both the adiabatic scanning calorimetry and modulation calorimetry. The specific heat has a very broad peak around 660°C of which the peak value is 46 J/mol.K. The results are totally different from the previous results that the specific heat is as large as 140 J/mol.K at the liquidus temperature and decreases rapidly with raising temperature. Combining the molar volume and sound velocity as a function of temperature, the thermodynamic susceptibilities, i.e. constant pressure specific heat, isothermal compressibility and thermal expansion coefficient, have been evaluated. Their temperature dependences and magnitudes are in good accordance with the predictions for a crossover transition in a liquid. Comparison is made to a liquid-liquid crossover transition in Ge 15 Te 85 which is sharpest among crossover liquid-liquid transitions of this kind so far found.

Highlights

The eutectic Ge-Te alloy (~15 at.% Ge) undergoes the sharpest crossover transition so far found
The transition is manifested by a pronounced exremum in the three thermodynamic susceptibilities [1]
T.) have shown that the peak values of these thermodynamic susceptibilities are interconnected by the thermodynamic relations known as the Ehrenfest-Pippard relations in the extended forms [2]

Summary

Introduction

The eutectic Ge-Te alloy (~15 at.% Ge) undergoes the sharpest crossover transition so far found. The transition is manifested by a pronounced exremum in the three thermodynamic susceptibilities (constant pressure specific heat, Cp, isothermal compressibility, κT, and thermal expansion coefficient, αp) [1]. One of the relations is that the Prigogine-Defay ratio, R= δCpδκT/(δαp2TV), is unity, where δ refers to the quantity associated with the crossover transition. The constant pressure specific heat, Cp, isothermal compressibility, κT, and thermal expansion coefficient, αp of liquid Ge15Te85 satisfy this relation. It implies that if structural changes cause a peak in Cp, a peak should appear in κT and αps. Only structural changes with a negative peaked αp have been found so far

Methods

Results

Conclusion