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Internal friction spectroscopy in Li20-2SiO2 partially crystallised glasses.

Research output: Contribution to journalJournal article

  • K. Müller
  • N. S. Bagdassarov
  • M. R. James
  • H. Schmeling
  • J. Deubener
<mark>Journal publication date</mark>1/05/2003
<mark>Journal</mark>Journal of Non-Crystalline Solids
Issue number1-2
Number of pages13
Pages (from-to)44-56
<mark>Original language</mark>English


Oscillatory torsion deformation experiments were performed on partially crystallised Li2O–2SiO2 glasses in the temperature range 350–480 °C and with frequencies between 20 and 0.002 Hz. The experiments were carried out in a torsion deformation apparatus exerting a small strain on cylindrical samples. Data obtained at varying temperatures and frequency were reduced to master plots using a normalised frequency. The frequency shift factor has been taken as a function of temperature in an Arrhenian form, yielding an activation energy of a background Q−1 close to the activation energy of oxygen defect diffusion (=120 kJ/mol). The master curves of real and imaginary components of shear modulus and internal friction indicate a stretched exponential shear stress relaxation with a an exponent of ≈0.45, characteristic of a broadened relaxation spectrum. The dynamic viscosity was estimated at temperatures of 470 and 480 °C. The extrapolation of dynamic viscosity to zero frequency allowed estimation of the relaxed shear viscosity. The presence of crystals increases the relaxed shear viscosity by ≈0.2log(Pa s)/10 vol.% of crystallinity. Dependence of the relative shear viscosity of partially crystallised lithium disilicate melts on crystal content is discussed.