A STUDY OF THE EFFECT OF MECHANICAL ABRASION ON THE RELAXATION BEHAVIOR OF NATURAL GALENA ELECTRODES - RELATIONSHIP WITH FLOTATION

Different types of surface pre-treatments of galena electrodes, chosen on the basis of literature data, lead to different behaviours in the time dependence of impedance spectra. The results show the influence o f a damaged layer due to mechanical polishing. The same equivalent cir cuit is found whatever the pre-treatment even in the range of positive potentials where oxidation of galena occurs. As in previous studies, the potential dependence of the capacitance shows that natural galena is an n-type semiconductor. However, the photocurrent is negative. Its potential dependence is bell-shaped, suggesting the effect of a proce ss similar to passivation. Some similarities in behaviour are noted be tween the impedance in the lower frequency range (<1 kHz) and the phot ocurrent obtained with modulated illumination.