On the electrochemical behaviour of undercooled melts and glasses

The electrochemical behaviour of undercooled melts and glasses is considered in detail. First the thermodynamic properties of the corresponding phases are calculated and then the temperature course of the emf and of other thermodynamic functions of a galvanic cell in which the net reaction is: undercooled melt (glass)→crystal, are determined. Some additional problems concerning the electrochemistry of amorphous electrodes are analyzed, e.g. hydrogen overvoltage upon hydrogen evolution on crystalline or amorphous electrodes of a given metal. Several variants are discussed for the possible experimental realization of a galvanic cell in which the emf is determined by the difference in the chemical potentials of the undercooled melt (or the glass) and the crystal, i.e. of a galvanic cell with a vitreous and a crystalline electrode made of one and the same electronic conductor or of a bipolar cell with an amorphous and a crystalline electrolyte, etc. An attempt is made to estimate the interal electric (Galvani) potential at the melt/crystal interface by using data for the difference of the Peltier coefficient between the respective phases.The analysis of the electrochemical behaviour of vitreous, liquid and crystalline electrodes is performed on the basis of formal thermodynamics and in terms of classical model approaches. It is shown how to determine by electrochemical measurements the main thermodynamic parameters of glasses which are considered as frozen-in non-equilibrium systems.