| Abstract: | A method by which the occurrence of a secondary relaxation can be deduced from the isochronal dielectric and mechanical loss data of amorphous and crystalline materials is given. The method eliminates the complexity arising from the frequency-independent, temperature-dependent background loss in solids. It is shown that the relaxation rate measured at a fixed frequency by varying the temperature substantially differs from that measured at a fixed temperature by varying the frequency when the strength of the relaxation is temperature dependent. This discrepancy leads to a different value of activation energy and of preexponential factor when the strength increases with temperature. The results are discussed in terms of the temperature dependence of the strength of relaxation and its distribution parameter. The method of analysis has been applied to the data for a molecular and a polymeric glass and shows the occurrence of a β process which is otherwise not detected in their tan β isochrones. Experimental data on a wide variety of glasses also show that the activation energies and relaxation rates obtained from isochrones differ from those obtained from the isothermal spectrum. |
