High dielectric composition in the system sn-modified (1-x)BaTiO ₃-xBa(Cu_1/3Nb_2/3)O₃, x=0.025 for multilayer ceramic capacitors

We report the synthesis and characterization of BaTiO₃ (BT)-based high dielectric compositions that are promising for Y5V-type multilayer ceramic capacitors. A solid solution with a nominal composition (1-x)BaTiO₃-xBa(Cu_1/3Nb_2/3)O₃ (BCN) (x=0, 0.025) was synthesized by conventional mixed oxide route, followed by compositional modification with varying concentration of Sn, as given by the formulation: 0.975 BaTi_1-ySn_yO₃-0.025 Ba(Cu_1/3Nb_2/3)O₃ (y=0.05, 0.06, 0.075, 0.1). Room-temperature (RT) X-ray diffraction patterns showed a decrease in the tetragonality of BT after modifying with BCN (BTBCN). Modifications with Sn lead to a further decrement in tetragonality and the RT structure became cubic at 6.0 at.% doping level. The decrement in tetragonality was accompanied by lowering of Curie temperature (T_c). BTBCN doped with 6 and 7.5 at.% Sn were found to exhibit diffuse phase transition accompanied by a high dielectric constant ≥7000, a low loss tangent ≤1% and a grain size in the submicrometer regime (≤1 μm).