Advances in the control of electrophoretic process parameters to tune the ytterbium disilicate coatings microstructure

Suspensions of ytterbium disilicate in isopropanol were prepared using iodine dispersant. Their zeta potential, electrical conductivity, and pH dependence with iodine concentration is detailed. Electrophoretic deposition was performed on silicon substrates at various voltages (100‐200 V) and times (until 10 minutes) and the growth dynamic was investigated. It was observed that the deposited mass reaches a maximum value for [I2] = 0.2 g/L, and the coating microstructure becomes porous at higher iodine concentrations. Current density and voltage measurements allowed to correlate this behavior to the increase of free protons concentration in the suspension. In these conditions, it was proved that porosity increases with the increase in applied voltage, and a compaction occurs as the deposition time increases. This has been related to the coating resistance increase and subsequent decrease in effective voltage in the suspension. The denser coatings (20% of porosity) were obtained in the case of suspension without iodine, at the minimum applied voltage and for the longest deposition times.