Effect of ball-milling time and surfactant content for fabrication of 0.85(Bi_0.5Na_0.5)TiO₃:0.15BaTiO₃ green ceramics by electrophoretic deposition

We fabricated thick and dense green ceramics consisting of the powders of (Bi_0.5Na_0.5)TiO₃ (BNT) and hexagonal BaTiO₃ (BT) with a molar ratio of 0.85:0.15 by electrophoretic deposition (EPD) in the suspension of iso-propanol of 200 ml with the mixed powders of 20 g, and investigated the effect of the ball-milling time and the surfactant (polyethylenimine, PEI) content for the suspension on the deposition weight and density of the green ceramics. When the ball-milling time was changed from 2 to 30 h with the PEI content of 0.2 g, the deposition weight was maximized at the ball-milling time of 15 h while the density monotonically increased with increasing ball-milling time for the EPD process of 1 h. When the PEI content was increased from 0.1 g to 0.2 and 0.3 g at the ball-milling time of 20 h, the deposit weight and density were increased. At the PEI content of 0.3 g, after the first EPD process was carried out and the cathode where the green ceramics were deposited was replaced without changing the suspension, the second green ceramics could be fabricated for the suspension ball-milled for 20 h, but not for the suspension ball-milled for 3 h. These results were explained by the size of the powders and the amount of PEI attached to the powders.