Structural and dielectric properties of barium strontium calcium titanate thick films modified with MnO2 for phased array antennas

(Ba,Sr,Ca)TiO3 powders, prepared by the sol-gel method, were mixed with an organic vehicle and the BSCT thick films were fabricated by the screen-printing techniques on alumina substrates. All the BSCT thick films, sintered at 1420 degreesC, showed the typical XRD patterns of a perovskite polycrystalline structure. The average grain size decreased with increasing amounts of MnO2, and the BSCT(50/40/10) thick film doped with 1 wt.% MnO2 showed a value of 6.5 mum. The thickness of thick films by four-cycle on printing/drying was approximately 100 mum. The Curie temperature and the relative dielectric constant decreased with increasing Ca content and MnO2 doping amount. The relative dielectric constant, dielectric loss and tunability of the BSCT(50/40/10) thick films doped with 1.0 wt.% MnO2 were 1296%, 0.61% and 11.18%, respectively. (C) 2003 Elsevier B.V. All rights reserved.