Thermodynamics of redox equilibria and diffusion of polyvalent ions in a phosphate glass melt

A phosphate glass melt with the basic composition of NaPO 3 .2Sr(PO 3 ) 2 doped with various oxides of polyvalent elements (Fe 2 O 3 , As 2 O 3 , Sb 2 O 3 , CuO and SO 4 2- ) was studied with the aid of square-wave voltammetry. The standard potentials depended linearly on temperature. The standard enthalpy ΔH° and the standard entropy ΔS° of the attributed redox reactions were calculated from the standard potentials measured. The diffusion coefficients were determined from current densities obtained and fulfilled the Arrhenius' law. Both thermodynamics of the redox equilibria and diffusion coefficients are compared with those measured in soda-lime-silica glasses.