SULFONE-BASED ELECTROLYTES FOR ALUMINUM ELECTRODEPOSITION

We developed new electrolytes for aluminum deposition based on AlCl3/dialkylsulfones (XSO(2)) mixtures usable in the 40-150 degrees C temperatures range along the melting point of the sulfone choosen. NMR study of these electrolytes showed that they contain AlCl4- Al(XSO(2))(2)(3+) and 1:1 molecular adducts AlCl3-XSO(2); this latter Al species is formed at the expense of Al(XSO(2))(3)(3+), especially in diethylsulfone and dipropylsulfone-based electrolytes. The Al species responsible for aluminum deposition has been shown to be Al(XSO(2))(3)(3+). Al deposits formed from AlCl3/XSO(2) electrolytes exhibit fine grain size, relatively smooth surface aspect and high purity. High deposition rates (>50 mu m h(-1)) and thick Al deposits with thickness up to few hundreds micrometers were obtained from AlCl3/dimethylsulfone at 130 degrees C.