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

Abstract

A phosphate glass melt with the basie composition of NaPO₃ · 2Sr(PO₃)₂ doped with various oxides of polyvalent elements (Fe₂O₃, AS₂O₃, Sb₂O₃, CuO and SO₄²¯) was studied with the aid of Square-wave voltammetry. The Standard potentials depended linearly on temperature. The Standard enthalpy ΔH⁰ and the Standard entropy ΔS⁰ 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.