Frequency dependence of heat capacity of the Pd40Ni10Cu30P20 amorphous alloy by temperature-modulated calorimetry

Abstract

The newly developed temperature-modulated differential scanning calorimetry (DSC) has been used to investigate the frequency dependence of heat capacity in the glass transition region for the Pd40Ni10Cu30P20 alloy upon heating and cooling. In contrast to conventional DSC results, the present work showed a dissipative behavior of the heat-flow response of the deeply supercooled Pd40Ni10Cu30P20 liquid in the glass transition region, qualitatively similar to the results obtained by specific heat spectroscopy on glycerol. A strong dependence of the temperature modulation period on the temperature of the peak imaginary part of complex heat capacity, Tmax, was found indicating a slowdown of the supercooled liquid dynamics as temperature decreased. This frequency dependence of Tmax can be well described by either the Arrhenius law or the Vogel-Fulcher-Tamman (VFT) equation. Furthermore, the VFT fit to the experimental data showed that the VFT temperature T0 was coincident with the thermodynamically determined Kauzmann temperature TK. The average characteristic time of enthalpy relaxation was determined to be approximately 50 s at 579 K and the apparent activation energy of glass transition was estimated to be 577±22kJ/mol. ©2000 The American Physical Society.