Impedance study of the electrophoretic deposition of yttrium silicate from a polymeric precursor sol

A polymeric yttrium silicate sol was prepared for the electrophoretic deposition of Y2SiO5 on C/C composite materials. The properties of the sol and the process of electrophoretic deposition (EPD) from the sol on glassy carbon substrates were studied using impedance spectroscopy. During constant voltage electrophoretic deposition first a rapid and thereafter a more gradual decay in current was observed, accompanied by the formation of a thin layer of an Y2SiO5 green body. Impedance spectroscopy after the end of the EPD experiment revealed that the resistance of the green body did not significantly increase the impedance of the EPD setup. The impedance spectra measured after EPD changed rapidly with time within the first few minutes, showing a decrease in the resistance of the green body and an increasing charge transfer resistance at the electrodes. This behavior could be related to the formation of a reaction product of electrochemical processes taking place during EPD, and points to ion depletion in the deposit layer.