Thermodynamics of various polyvalent main group elements in a borosilicate glass melt

The thermodynamics of redox equilibria were studied by square-wave-voltammetry in a borosilicate glass melt at temperatures in the range of 700 to 1100 degrees C. The glass melts were doped with oxides of As, Sb, Bi, Te, Sn and Pb. While lead and bismuth are reduced in one redox step to the metallic state, glass melts doped with the other elements have two well separated redox steps. Standard potentials linearly depend on temperature and hence both the standard enthalpy and the standard entropy are constant. The electrochemical series of elements is nearly the same as that reported in soda-lime-silica glass melts. With the exception of the Pb2+/Pb-0-redox step, all standard potentials in the borosilicate glass melt are notably shifted to more negative potentials by comparison with those reported from soda-lima-silica glass melts.