Dielectric and anti-reduction properties of BaTiO3-based ceramics for MLCC application

BaTiO3 ceramics doped with different contents of Co2O3(abbreviated as (1-x) BT-xCo2O3) and (1-x) BaTiO3-xBiCoO3(abbreviated as (1-x) BT-xBC) ceramics were prepared via conventional solid-state process and sintered in reducing atmosphere. The main crystal phase of both ceramic samples was characterized by X-ray diffraction (XRD), which was perovskite structure. Compared with (1-x) BT-xCo2O3, (1-x) BT-xBC ceramic samples were dense with uniform microstructure confirmed by scanning electron microscopy (SEM). The 0.95BT-0.05BC ceramics had good dielectric properties, with ε25°C = 2670, tanδ = 0.012, and resistivity was 1.71 × 1011 Ω cm at 25°C, meeting the X7S standard for multilayer ceramic capacitor (MLCC) applications. The mechanism of improved anti-reduction property of (1-x) BT-xBC ceramics was studied by X-ray photoelectron spectroscopy (XPS) and thermally stimulated depolarization current (TSDC) techniques. The XPS results showed that there were two valence states of Co in 0.95BT-0.05BC and 0.95BT-0.05Co2O3 ceramics, indicating that the introduction of Co can improve anti-reduction property of BT-based ceramics. The TSDC revealed the formation of defect dipoles [2CoTi'−Vo▪▪], which was considered to be the cause for the improvement in anti-reduction property.