Colossal Permittivity and Low Loss in BaTiO ₃ Ceramics With X9F Temperature Stability

Colossal permittivity (CP) materials have attracted significant attention due to their crucial role in advancing electronic device miniaturization and performance enhancement. Herein, we present a novel CP material (Ba _0.99 La _0.01 Zr _x Ti _{1− x} O ₃ (BLZT)), which exhibits high CP performance in optimal composition ( x  = 0.075) that with a colossal dielectric permittivity of 4.1 × 10 ⁵ and a low loss tangent of 0.057 at 1 kHz, as well as X9F‐type temperature stability [( ε′‐ε′ _25 °C )/ ε′ _25 °C ≤ 7.5% in a range −55–200 °C]. A systematic investigation of the mechanism of CP was conducted using XPS and complex impedance spectroscopy, demonstrating that the outstanding CP performance originates from multiscale polarization mechanisms induced by A/B‐site synergistic doping. Electron‐pinned defect dipoles (EPDD) associated with La ³⁺ donor doping dominate high‐frequency localized polarization. Grain refinement and grain‐boundary engineering enhance the internal barrier layer capacitance (IBLC) effect, improving intermediate‐ to low‐frequency interfacial polarization. This work demonstrates an effective strategy that, through A/B‐site synergistic defect engineering, achieves X9F colossal dielectric BaTiO ₃ ‐based ceramics.