N-State Models and the Vitreous State: The Interrelation of the Relaxational Properties of B2O3

摘要

A three state model for the relaxational heat capacity, thermal expansion, and compressibility of vitreous B2O3 is presented. 'N-state' systems are natural candidates for models of vitreous materials. These models offer a complete description of equilibrium behavior. Hence, a successful description of a single thermodynamic response by such a model is not entirely satisfactory, unless the other responses are also described by the model. It is shown that the relaxational responses of vitreous B2O3 cannot be simultaneously described by any two state model (or by any model involving a single ordering parameter), but can be described over a wide range of temperature by a simple ideal-mixing three-state model. The model also describes Raman data with no further adjustments. The failure of the model at low temperatures, still above T sub g, probably represents the onset of non-ideal mixing of the states. This model presents a view of the glass transition which does not involve a phase transition; the properties of the vitreous phase extend smoothly to arbitrarily low temperatures. (Author)