Crossover and normal structural relaxation in naturally aged glassy Pd40Cu30Ni10P20

• Long-time storage of glassy Pd40Cu30Ni10P20 leads to crossover relaxation.
• Crossover relaxation is accompanied by low temperature heat absorption.
• At high temperatures, crossover relaxation changes into a normal one.
• Formation enthalpy of underlying defects is very close to that given by Interstitialcy theory.

Measurements of Young’s modulus relaxation at elevated temperatures in glassy Pd40Cu30Ni10P20 stored at room temperature for nine years are performed. It is found that testing in a wide range above room temperature leads to the crossover relaxation, which is absent in the as-prepared glass. At high testing temperatures, the crossover behavior changes into normal log-time relaxation kinetics. The crossover relaxation is accompanied by low temperature endothermal heat reaction, which is followed by exothermal heat flow characteristic of normal structural relaxation below the glass transition. Structural rejuvenation of samples by rapid quenching from the supercooled liquid state drastically changes the relaxation kinetics removing the crossover almost completely.It is revealed that the formation enthalpy of structural defects responsible for the crossover relaxation is very close to that derived in shear modulus relaxation experiments as well as to the formation enthalpy given by the Interstitialcy theory. This provides further support for the interpretation of structural relaxation behavior within the framework of this theory.