Microstructure and electrochemical behaviour of some SnO2-based inert electrodes in aluminium electrolysis

Some types of anodes that could replace the usual carbon anodes in aluminium production by the Hall-Heroult process are based on SnO2. The present investigation deals with SnO2-Sb2O3-CuO ceramics having an SnO2 content of greater than or equal to96%), Sb2O3 and CuO being dopants. The ceramic pellets, thermally treated at 1400 degreesC for 4 hours, were analysed by X-ray diffraction and IR spectroscopy. The structural analysis of the samples evidenced an SnO2((SS)) type solid solution. All samples were electronically conductive (small negative values of the, Seebeck coefficients), having an activation energy ranging within 0.02-0.3 eV. The anodic polarisation curves obtained with those: anodes in an electrolyte of 88% Na3AlF6, 7% Al2O3 and 5% CaF2 were studied. The results were correlated with the microstructure of the investigated samples.