Ionic Motion in Materials with Disordered Structures
Diffusion and Ionic Conduction in Standard Silica Glasses
The tracer diffusivities of 22Na and 45Ca in two high-quality standard silica glasses
produced by the DGG (Deutsche Glastechnische Gesellschaft) have been measured in the temperature range
between 473 and 783 K. The temperature dependences of the tracer diffusion coefficients in both glasses
follow Arrhenius laws. The diffusion of 22Na is six to seven orders of magnitude faster than the
diffusion of 45Ca. The ionic conductivity was determined by impedance spectroscopy and the
conductivity diffusion coefficient D s was deduced from the
dc conductivity via the Nernst-Einstein relation. The temperature dependences of D s for both glasses follow also Arrhenius functions. The activation parameters
and pre-exponential factors for tracer diffusion and for conductivity diffusion were determined. The activation
enthalpy of 22Na diffusion is almost equal to the activation enthalpy of the
dc conductivity. We conclude that the conductivity of standard glasses is due to the motion of
Na ions. The diffusivities of 22Na and 45Ca in soda-lime glasses increase with
increasing Na2O content.
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