Indentation creep of Ge-Se chalcogenide glasses below Tg:: elastic recovery and non-Newtonian flow

Chalcogenide glasses from the Ge-Se system behave viscoelastically at room temperature. It follows that indentation measurements are time- or rate-dependent. The study of the dependence of hardness (H) on the loading duration for GexSe1-x, glasses with x between 0 and 0.4 shows that the penetration displacement is the sum of an elastic component which reaches values as high as 60% of the total displacement, and a creep one, which is strongly non-Newtonian (shear thinning), and leads to a significant decrease of H with an increase of the loading time. The apparent viscosity and activation energy for flow were derived from the H(t) data on the basis of a theoretical analysis of the indentation process, and the results are in good agreement with those obtained from conventional viscosity measurements. (C) 2002 Elsevier Science B.V. All rights reserved.