Frequency dependence of heat capacity of thePd40Ni10Cu30P20amorphous 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 ${\mathrm{Pd}}_{40}{\mathrm{Ni}}_{10}{\mathrm{Cu}}_{30}{\mathrm{P}}_{20}$ 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 ${\mathrm{Pd}}_{40}{\mathrm{Ni}}_{10}{\mathrm{Cu}}_{30}{\mathrm{P}}_{20}$ 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, ${T}_{\mathrm{max}},$ was found indicating a slowdown of the supercooled liquid dynamics as temperature decreased. This frequency dependence of ${T}_{\mathrm{max}}$ 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 ${T}_{0}$ was coincident with the thermodynamically determined Kauzmann temperature ${T}_{K}.$ 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 $577\ifmmode\pm\else\textpm\fi{}22\mathrm{k}\mathrm{J}/\mathrm{m}\mathrm{o}\mathrm{l}.$