Alternating Current Electrophoretic Deposition of Gadolinium Doped Ceria onto Yttrium Stabilized Zirconia: A Study of the Mechanism

Direct current electrophoretic deposition (DC-EPD) has been successfully adopted to deposit Gd-doped ceria (GDC) onto yttrium stabilized zirconia (YSZ) previously. However, bubble evolution associated with the proton reduction results in deterioration of the quality of the GDC layer. For the purpose of lowering the densification temperature of the GDC layer by improving its green density, alternating current electrophoretic deposition (AC-EPD) is used to eliminate the bubble evolution. A dense GDC layer with a thickness of 6 mu m is successfully obtained after sintering at 1250 degrees C. The barrier layer effectively eliminates the reaction between LaxSr1-xCoyFe1-yO3-delta (LSCF) and YSZ. The voltage waveform consists of a negative voltage step and a positive voltage step of varying magnitude and step length. The optimum frequency of 500 Hz leads to the maximum deposition yield which is linear with regard to deposition time. Moreover, with the increase of the negative to positive voltage ratio and the length of the negative step relative to the length of the positive step, the deposition rate grows correspondingly. Because the AC step voltages result in negligible faradaic reactions, the deposition process is controlled by the transport process and the desorption process, wherein the latter process is irreversible.