Structural relaxation of B2O3 on a freestanding sample in the glassy state

We have studied the structural relaxation of B2O3 as a function of temperature by means of multi-speckle photon correlation spectroscopy (PCS). The method allows us to probe relaxation times at temperatures well below the glass transition on a bulk sample which is not enclosed in any container. Above the glass transition temperature, the enhanced mobility promotes the degradation and crystallisation of the surface. In this regime the bulk dynamics follows the usual VogelFulcher-Tamman (VFT) relation, while the surface relaxation presents a compressed shape, suggesting a stress dominated dynamics. The experiment paves the way to study dynamical relaxations on glasses with elevated melting temperature.