Cobalt ferrite dispersion in organic solvents for electrophoretic deposition: Influence of suspension parameters on the film microstructure

An electrophoretic deposition (EPD) method was applied for the preparation of CoFe2O4 (CFO) films on Al2O3/Pt substrates. A coprecipitation process was used to synthesize fine CFO powders with an average particle size of ∼40 nm. Influences of suspension parameters such as solvents, iodine additive, and charged polymer on the suspension stability and film microstructure were investigated in detail. Three suspensions including CFO-acetylacetone, CFO-acetylacetone-0.08 wt% I2 and CFO-acetylacetone-0.2 wt% polyethylenimine (PEI) were optimized, respectively. It was found that CFO was deposited uniformly and the potential required for the deposition was small for the three optimized suspensions. After sintering at 1250 °C for 2 h, the film from CFO-acetylacetone-0.08 wt% I2 showed many cracks, which indicates this suspension is not suitable for preparing high quality CFO ceramic films. While the sintered films fabricated from the other two optimized suspensions exhibited dense structures. Based on the electric and magnetic properties of CFO ceramic films, it can be concluded that CFO-acetylacetone-0.2 wt% PEI is the proper suspension to prepare films with better microstructures and properties.