Calorimetric, thermomechanical, and rheological characterizations of bulk glass-forming Pd40Ni40P20

Calorimetric, thermomechanical, and rheological properties of undercooled l iquid Pd40Ni40P20 were determined within a wide temperature range above the glass transition. The concept of the limiting fictive temperature was appl ied to the entire set of measurements to compare the different properties a dequately. It was found that an equilibrium state of a sample that is defin ed by its calorimetric glass temperature corresponds to a similar equilibri um state for the specific volume and for the shear viscosity as well. The K auzmann temperature as one of the most important material characteristics c oncerning the glass transition could be determined with high accuracy leadi ng to the evaluation of the free volume persistent in the samples. Viscosit y values of the liquid extending over a range of about nine orders in magni tude could be described best by the free volume theory evaluated by Cohen a nd Grest, provided that experimentally obtained parameters were used for th e calculations. The comparison between nonequilibrium measurements at isoch ronous heating and model calculations in the framework of bimolecular react ion kinetics shows that good agreement can be achieved using thermodynamic parameters that have been obtained from equilibrium measurements. However, systematic deviations indicate also the limitations of the model that are r elated to the intrinsic dynamic heterogeneity of the vitreous state. (C) 20 00 American Institute of Physics. [S0021-8979(00)09803-0].