High-temperature elasticity and viscosity of GexSe1-x glasses in the transition range

Article

关键词: AMORPHOUS SELENIUM;    CHALCOGENIDE GLASSES;    LIQUID SELENIUM;    FORMING LIQUIDS;    POISSONS RATIO;    SHEAR MODULUS;    VISCOUS-FLOW;    SE;    INDENTATION;    ACTIVATION;   

DOI  :  10.1103/PhysRevB.84.064201

来源: SCIE

【 摘 要 】

The viscous-flow behavior and temperature dependence of the elastic moduli of chalcogenide glasses from the germanium-selenium system were studied by means of homemade high-temperature indentation setup and resonant-frequency technique (1-10 kHz), respectively, for temperatures between 0.8 and 1.2 x T-g. The softening rates, both in the elastic and in the viscous-flow regimes, were correlated to network destructuration or reorganization events in the light of previously reported high-temperature neutron-scattering data. The concomitant change of Poisson's ratio (nu) and the thermodynamic parameters of the thermally activated viscous-flow process were characterized and provide a new basis for the understanding of the sources for the softening in the transition range. The temperature dependence of nu suggests weak changes of the network cross-linking degree at large Ge contents. On the contrary, in the case of a-Se, a steep fragmentation of the structural units is inferred from the nu(T) data, and the flow process is accompanied by a huge entropy change (activation entropy at saddle point). The entropy contribution at T-g (T-g x Delta S-a) represents more than 50% of the activation enthalpy for flow (Delta H-a) and increases with the selenium content. Hence the free activation energy (Delta G(a)) is much smaller than apparent activation energy as derived from viscosity data.

【 授权许可】

Free