Linear Viscoelasticity of an Ultraphosphate Glass
Linear viscoelastic stress relaxation and oscillatory shear experiments were performed on a mixed alkali ultraphosphate of composition 0.2Na2O + 0.2Li2O + 0.6P2O5 at temperatures in the vicinity of the glass transition temperature, Tg. The stress relaxation data were well described by a stretched exponential function G(t) = G0exp[-(t/τ)]β. β decreased with increasing temperature. Oscillatory shear experiments were performed to determine the complex mechanical moduli, G*(ω) = G′(ω) + iG″(ω), as a function of angular frequency, ω. G′(ω) is the elastic modulus and G″(ω) is the loss modulus. The breadth of G″(ω), which is a direct measure of the distribution of relaxation times, increased with temperature in the same temperature range. The temperature dependence of β and of G″(ω) indicates a failure of thermorheological simplicity in this glass. The shear viscosities of the glass determined from G(t) and the zero shear viscosities determined from G″(ω) were found to be in agreement.
P. F. Green et al., "Linear Viscoelasticity of an Ultraphosphate Glass," Journal of Non-Crystalline Solids, Elsevier, Jan 2000.
The definitive version is available at http://dx.doi.org/10.1016/S0022-3093(99)00635-3
Materials Science and Engineering
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