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Self-diffusion of iron in alkali–magnesia–silica glass melts

1998; Elsevier BV; Volume: 226; Issue: 1-2 Linguagem: Inglês

10.1016/s0022-3093(98)00368-8

1873-4812

Sandra Gerlach, Olaf Claußen, Christian Rüssel,

Material Dynamics and Properties

Alkali–magnesia–silica glass melts with lithium (74 SiO2, 16 Li2O, 10 MgO), sodium ((90−x) SiO2, x Na2O, 10 MgO (x=10, 15, 20, 25)), potassium ((90−x) SiO2, x K2O, 10 MgO (x=10, 15, 20, 25)) and caesium (74 SiO2, 16 Cs2O, 10 MgO) (all compositions given in mol%) doped with 0.2 mol% Fe2O3 were studied by means of square-wave voltammetry. Decreasing Na2O- and K2O-contents lead to a decrease in the self-diffusion coefficients of iron and an increase in the viscosities of the liquids. A comparison of diffusivities of different alkali ions shows that at constant temperature, the self-diffusion coefficients decrease from lithium to caesium. Within the error limits, in most of the glasses studied, the Stokes–Einstein equation is fulfilled with respect to the dependence of the diffusivity on the viscosity. At constant viscosity, i.e., mobility of the glass network, the self-diffusion coefficients decrease with increasing alkali concentrations and decreasing size of the alkali cation. These effects are discussed using a structural model for the incorporation of iron into alkali containing glasses.