Improvement in Dielectric Tunability of Ba_0.6Sr_0.4TiO₄-Mg₂TiO₄ Composite Ceramics via Heterogeneous Nucleation Processing

Dielectric tunable composite ceramics Ba_0.6Sr_0.4TiO₃-Mg₂TiO₄ (BST-MT) are prepared with a heterogeneous nucleation sol-gel approach. The Mg₂TiO₄ powders are synthesized by the conventional solid-state reaction method. The micro-sized MT powders with dispersant Ciba-4010 are introduced into Ba-Sr-Ti sol to obtain uniform and homogeneous mixture compounds with nano-sized BST particles synthesized via heterogeneous nucleation (HN) in the sol-gel process. Thus, the microstructural and dielectric properties can be tailored. The dielectric constants of BST-MT composite ceramics can be adjusted in a large range from 294 to 1790, and the dielectric tunability can be adjusted from 29.4% to 37.0% with different MT contents from 60wt% to 20wt%. Compared to the samples prepared by the conventional solid-state (SS) process, the BST-MT composite ceramics by the heterogeneous nucleation sol-gel process exhibit a more uniform microstructure, and improve dielectric properties.