Effect of thermodynamic history on secondary relaxation in the glassy state

We investigated by dielectric spectroscopy the effect that the thermodynamic history of a glass has on the secondary relaxation process. In particular we focused our attention to glassy states at the same conditions of temperature and pressure but reached with different combinations of variation of the external parameters. Our analysis shows that the effect of thermodynamic history on the relaxation frequency is related to the activation volume of the process: secondary processes with larger activation volume present a larger effect of the thermodynamic history. This demonstrates an important role of density in determining such behavior in glassy systems. (c) 2007 Elsevier B.V. All rights reserved.