Experiment and Its Analysis

The polarisation curves for the melts of the systems TI2S-TII and Ag2S-AgCl were obtained by linear sweep voltammetry [14]. 

The cathodic polarisation curves of the melts TI2S-TII at 60 mol% of TIJ and at three different temperatures are given in Fig. 5.1. 

Linear fit of the initial parts of the curves in Fig. 5.1, which apparently correspond to the electronic current prior to the beginning of electrochemical decomposition, has been performed using Eq. (5.1) expressed in a linearised form 

The values of limiting electronic current densities Eq. (5.2) were calculated from the slopes of the straight lines plotted in Fig. 5.2. 

The parameter 8 which we can see in Eq. (5.2) can be interpreted as one-half of the effective thickness of the sample if the sample is solid and if the stationary distribution of the charge carriers has already been established. In case of a melt where convective mixing in the bulk occurs, the value 5 should correspond to the thickness of the diffusive layer where mixing is absent. The exact value of 5 in sulphide melts at free convection conditions was not a subject of experimental investigatirms the order of value about 10 cm can be estimated from hydrodynamic considerations. That is why we are not able to extract the precise value of xj from the data on limiting electron currents ioo- 

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This experiment and its analysis constituted the thesis project of CMU graduate student Jean Seydoux who received his Ph.D. this year. 

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