Dielectric properties of (Ba,Sr,Ca)TiO3 ceramics modified with MgO for phased array applications

(Ba0.6-xSr0.4Cax)TiO3 (BSCT)+y wt% MgO (x = 0.10, 0.15, 0.20, y = 0.0similar to3.0) ceramics were fabricated by using the conventional solid-state reaction, and their structural and dielectric properties were investigated for various composition ratios and MgO doping contents. A second phase, representative of MgO, appeared in 3 wt% MgO-doped BSCT specimens. The average grain sizes decreased with increasing amounts of MgO, and the BSCT(40/40/20) specimens doped with 3 wt% MgO showed a value of 9.3 mum. The Curie temperature and the relative dielectric constant also decreased with increasing MgO doping content, and the relative dielectric constant decreased nonlinearly as the field strength increased. The tunability increased with decreasing Ca content, and the BSCT(50/40/10) specimen doped with 1.0 wt% MgO showed the highest value of 6.4% at 5 kV/cm.