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In this study, a novel lead‐free high‐entropy ceramic (HEC) system, (Bi0.2Na0.2Ca0.2Ba0.2Sr0.2)(1–3x/2)LaxTiO3 (0 ≤ x ≤ 0.15) (abbreviated as BNCBST‐xLa), was designed to enhance energy storage performance through La substitution and prepared via a hydrothermal method. Results indicate that La doping at A site in BNCBST induces lattice distortion and further improves dielectric relaxation. Moreover, grain growth is inhibited by the La content, which results in an increase in the insulation resistance and thus significant enhancement in the electric breakdown strength (Eb). Accordingly, the system with x = 0.03 exhibits an excellent recoverable energy density (Wrec) of 2.43 J/cm3 and a high energy storage efficiency (η) of 85.5% under a great Eb of 245 kV/cm, together with wide temperature stability (Wrec and η vary within ± 8.3% and ± 1.1% at 30–150°C). The findings of this study suggest that the obtained La‐modified BNBCST HECs are promising for energy storage applications.

In this study, 0.94Mg (1-3x/2) Ce x TiO 3 −0.06(Ca 0.8 Sr 0.2 )TiO 3 (MCe x T−CST, 0≤x≤0.01) composite ceramics were prepared at a low temperature of 1175 • C by using the 50-nm-sized powders. The effects of Ce 3+ doping on crystalline phase, microstructure, and microwave dielectric properties of MCe x T−CST were studied. A main ilmenite (Mg,Ce)TiO 3 phase and a minor perovskite (Ca 0.8 Sr 0.2 )TiO 3 phase coexist well with the appearance of impurity MgTi 2 O 5 phase in MCe x T−CST. The dielectric properties of MCe x T−CST are affected by the molecular polarizability, the impurity phase, and the Ce 3+ doping. The replacement of Mg 2+ by high valence Ce 3+ could effectively inhibit the formation of oxygen vacancy, resulting in the enhancement of Q×f. When x = 0.005, MCe x T−CST exhibits microwave dielectric properties with a moderate ε r of 21.5, a high Q×f of 67 000 GHz, and a near-zero τ f of −0.74 ppm/ • C. The results reveal that the Ce 3+ substitution is a prospective approach to optimize the microwave dielectric properties of MgTiO 3 -based ceramics. K E Y W O R D S0.94Mg (1-3x/2) Ce x TiO 3 −0.06(Ca 0.8 Sr 0.2 )TiO 3 , Ce 3+ doping, low-temperature sintering, microwave dielectric properties 1 3392