INFLUENCE OF THE PREPARATION CONDITIONS ON THE THERMAL-CONDUCTIVITY IN METALLIC GLASSES

We report measurements of the thermal conductivity on two amorphous Ni72Si8B20 samples of different thicknesses 90-mu-m and 25-mu-m in the temperature range between 0.3-KAPPA and 25-KAPPA. The thickness of the ribbons (Vitrovac 0080) was correlated to the quenching rate q resulting in q = 1.5 x 10(5) KAPPA s-1 and q = 8 x 10(5) KAPPA-s-1, respectively. The total thermal conductivity kappa-tot consists of two contributions, the phonon thermal conductivity kappa-ph and the electronic thermal conductivity kappa-el. At low temperatures T < 1 KAPPA-kappa-ph is limited by scattering of phonons from electrons and low-energy excitations (LEE). The phonon-LEE scattering coefficient increases with quenching rate by 80% while the phonon-electron scattering remains almost unchanged. These results can be understood by an enhanced density of LEE in the sample quenched with a higher cooling rate, giving further support for the validity of the free volume model to explain the origin of the LEE in amorphous metals.