Dielectric properties of screen-printed (Ba,Sr,Ca)TiO3 thick films modified with Al2O3 for microwave device applications

(Ba,Sr,Ca)TiO3 (BSCT) powders, prepared by the sol-gel method, were mixed with organic vehicle and the BSCT thick films were fabricated by the screen printing techniques on alumina substrates. The structural and the dielectric properties were investigated for various composition ratio and Al2O3 doping contents. All the BSCT thick films, sintered at 1420°C, showed the typical XRD patterns of a perovskite polycrystalline structure. The thickness of thick films by four-cycle on printing/drying was approximately 95–105 μm. The Curie temperature and relative dielectric constant decreased with increasing Ca content and Al2O3 doping amount. The relative dielectric constant, dielectric loss and tunability at 30 kV/cm of the BSCT(50/40/10) thick films doped with 1.0 wt.% Al2O3 were 829, 0.39% and 12.94% respectively.