Effects of solvent system on tape casting of the BaSrTiO₃-MgO-based dielectric ceramics containing B₂O₃

Ba_0.6Sr_0.4TiO₃-MgO-based ceramic slurries with B₂O₃ and Li₂CO₃ as sintering aid were prepared with different solvent systems for tape casting application. The effects of azeotropic mixtures of toluene–ethanol, methyl ethyl ketone (MEK)–ethanol and zeotrpic mixture of xylene–ethanol with a mass ratio of 50:50 on Ba_0.6Sr_0.4TiO₃-MgO-based nonaqueous suspensions with B₂O₃ and Li₂CO₃ as sintering aid were investigated by sedimentation test, rheological measurement, density measurement, and SEM analysis. Without organic additives added, suspensions prepared with the MEK–ethanol mixture present higher flowability with lower viscosity, but less stability because of the smaller viscosity and density of MEK. On the other hand, with organic additives added, the gel structure is formed in slurries prepared with the toluene–ethanol mixture and xylene–ethanol mixture, caused by the reaction of the functional hydroxyl group of PVB and dissociated borate in the slurries. While slurries prepared with the MEK–ethanol mixture were more stable, exhibiting nearly Newtonian flow behavior and significantly lower viscosity.