Structural evolution and dielectric properties of (Ce, Mg, Ca)-co-doped BaTiO3 ceramics for potential X8R capacitor applications

The microstructure engineering of BaTiO 3 -based ceramic systems serves as an essential prerequisite to attain superior dielectric stability and reliability in modern multilayer ceramic capacitors (MLCCs). In this study, the effects of Ca doping on phase composition, microstructure, defect evolution, and dielectric temperature stability were systematically investigated in a novel BaTiO 3 -1 at%CeO 2 -3 at%MgO- x at%CaCO 3 ( x = 0, 2, 4, 6, 8) ceramic system. The results show that Ca doping promotes the tetragonality of the structure to increase first and then decrease. The addition of Ca 2+ changed the original defect composition of the ceramics: Ca 2+ promotes the conversion of Ce 3+ to Ce 4+ , reduces the reduction of Ti 4+ , and regulates the concentration of oxygen vacancies. The addition of Ca 2+ reduces the grain boundary activation energy ( 1.86 eV to 1.33 eV ), and reduces the carrier concentration to improve the ceramic resistivity. Ca 2+ promotes the enrichment of doped ions at the grain boundary to form a ' core-shell ' structure, which is characterized by broadened and suppressed dielectric peaks. When x = 6 at %, the ceramics meet the X8R specification (|( C T - C 25°C )/ C 25°C ×100%| ≤ 15%, T ∈ [-55°C, 150°C]), the dielectric constant at room temperature is 2802, and the dielectric loss is less than 0.02. This study reveals the Ca 2+ induced multi-ion synergistic regulation mechanism, which provides an experimental basis for the development of high stability and low loss lead-free MLCC dielectric materials that meet the X8R standard.