Enhanced dielectric properties of highly dense Ba_0.5Sr_0.5TiO₃ ceramics via non-toxic gelcasting

In this paper, a non-toxic water-soluble copolymer of isobutene and maleic anhydride (Isobam) was used for gelcasting of Ba_0.5Sr_0.5TiO₃ (abbreviated as BST50) ceramics as both dispersant and gelling agent. The rheological properties and gelation behavior of BST50 suspensions have been investigated. BST50 suspension with 54 vol% solid loading and 0.1 wt% Isobam was optimized for the gelcasting process. Complex-shaped green bodies were prepared with homogeneous microstructure without large defects. BST50 samples sintered at 1500 °C were processed at a high relative density of 99.6%. The sample possessed a high dielectric tunability of 22% (30 kV/cm) and tanδ of 0.006 (1 kHz) which is decreased by 70% compared with that of dry-pressed samples. The present method has great potential in the preparation of other functional ceramics with complex shape and enhanced performance.