Diffusion of copper in soda–silicate and soda–lime–silicate melts

Abstract Copper diffusion coefficients were measured in glass melts with the base compositions x Na 2 O·(100 − x )SiO 2 , x = 15, 20, 26 and 33 mol% and (26 − x )Na 2 O· x CaO·74SiO 2 , x = 0, 5, 10 and 15 mol% doped with 1 mol% CuO in the temperature range from 900 to 1150 °C by square-wave voltammetry. The current–potential curves recorded exhibit two distinct maxima which are attributed to the reduction of Cu 2+ to Cu + and Cu + to metallic copper. The peak currents decrease with decreasing temperature. The mean diffusion coefficients for the Cu + /Cu 2+ -species are calculated from the peak currents and fitted to Arrhenius equation. The activation energies of the copper diffusion are in the range from 126 to 170 kJ mol − 1 . Diffusion coefficients related to the same viscosity decrease with increasing Na 2 O-concentration. The incorporation of copper into the melt structure is discussed.