Stability of Aqueous Barium Titanate Suspensions for MLCC Inkjet Printing

Abstract : BaTiO3-based materials are currently used for the fabrication of multilayer ceramic capacitors (MLCC) because of their high dielectric properties. The inkjet printing (IJP) process can be used to fabricate MLCC of complex configurations by integrating internal electrodes and dielectric layers in a single step using a multi printing-head system. Stabilized aqueous suspensions of BaTiO3-based powders are required to obtain dielectric inks adapted to IJP. This study investigates the influence of BaTiO3 powder hydrolysis in water on the surface chemistry and stability in relationship with the milling step used to adjust the powder grain size to IJP. Optimum parameters for a good stability of BaTiO3 suspensions are identified. The selected dispersant is a polyacrylate (PAA) for which the content is adjusted to minimize the sedimentation rates as required by IJP. Moreover, the addition of ethylene glycol is shown to be necessary to avoid the formation of a gel structure which could result from the interaction of borates ions leached from the surface of BaTiO3 with the PAA dispersant. A mechanism of gel formation is proposed.