A large thermal hysteresis between melting and solidification temperature on nanoscale Pb particles embedded in amorphous sio2 matrix prepared by sputtering

Abstract

The melting and solidification behaviors of (SiO2)100-xPbx sputtered films, where nanoscale Pb particles are embedded in amorphous SiO2 matrix, were studied using differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). With decreasing the size of Pb particles, lowering of the melting point and the degree of supercooling of Pb particles were significantly increased. A very large thermal hysteresis loop width of 213K that is, the depression of the melting point and the increase of supercooling of Pb particles with a diameter of 5nm was as large as 63K and 150K, respectively, was observed by DSC. These results were discussed in a phenomenological context considering the existence of the interface between Pb particles and amorphous SiO2 matrix. The depression of the melting point of Pb particles is due to the increase in the interfacial energy between fine Pb particles anti amorphous SiO, matrix. A large supercooling of Pb particles is interpreted as a heterogeneous nucleation process due to nearly impurity-free fine particles.