High-temperature dielectric ceramics are in urgent demand due to the rapid development of numerous emerging applications. However, producing dielectric ceramics with favorable temperature, frequency and electric field stability is still a huge challenge. The construction of multi-phase coexistence material systems is an effective way to obtain stable dielectric and energy storage properties. In this work, NaNbO₃ (NN) modified 0.95Bi_0.5Na_0.5TiO₃–0.05SrZrO₃ (BNTSZ) ceramics ((1 − x)BNTSZ–xNN) are designed to achieve the coexistence of rhombohedral and tetragonal phases. The variation in the dielectric permittivity of the 0.8BNTSZ–0.2NN ceramic is less than ±15% over the temperature range from −55 °C to 545 °C, which is the reported record-high upper operating temperature, with a high room-temperature dielectric permittivity of 1170. The 0.8BNTSZ–0.2NN ceramic exhibits excellent frequency and electric field stability as well. Additionally, a large discharge energy density of 3.14 J cm⁻³ is obtained in the 0.85BNTSZ–0.15NN ceramic with an energy efficiency of 79% at a high temperature of 120 °C under 230 kV cm⁻¹, with the variation in the discharge energy density being less than ±4% in the temperature range from 25 °C to 180 °C under 120 kV cm⁻¹. All these features demonstrate that the (1 − x)BNTSZ–xNN ceramics are promising candidates for use at extremely high temperature in both dielectric and energy storage capacitor applications.

Dielectric ceramic capacitors are fundamental energy storage components in advanced electronics and electric power systems owing to their high power density and ultrafast charge and discharge rate. However, simultaneously achieving high energy storage density, high efficiency and excellent temperature stability has been a huge challenge for the practical capacitor applications of dielectric ceramics. These concerns have been addressed herein in relaxor ferroelectric grain core–shell structured 0.87BaTiO₃–0.13Bi(Zn_2/3(Nb_0.85Ta_0.15)_1/3)O₃@SiO₂ multilayer ceramic capacitors (MLCCs) via our multiscale optimization strategy from atomic scale, to grain scale to device scale designs to increase the breakdown field strength and decrease the leakage current, which generates superior energy storage performance with a giant discharge energy density of 18.24 J cm⁻³, ultrahigh efficiency over 94.5%, and excellent temperature stability (<10%, 25 to 190 °C) and cycling stability. Compared with the 0.87BaTiO₃–0.13Bi(Zn_2/3(Nb_0.85Ta_0.15)_1/3)O₃ MLCC counterpart without SiO₂ coating, the discharge energy density was enhanced by 80%. The multiscale optimization strategy should be a universal approach to improve the overall energy storage performance in dielectric ceramic multilayer capacitors.

A record-high breakdown strength (790 kV cm⁻¹) and high energy density (5.04 J cm⁻³) are obtained in BTAS/BTBZNT ceramics with a layer-by-layer structure.

The utilization of multilayer ceramic capacitors (MLCCs) in energy-storage applications is drawing increasing attention since the energy density of MLCCs has been improved significantly. However, the low dielectric breakdown strength and high loss at high temperatures are still key challenges which limit the application of MLCCs in high-voltage or high-temperature systems. In this work, a two-step sintering (TSS) method with a fast first-step heating rate of 40 °C min⁻¹ is introduced to fabricate lead-free MLCCs. Compared with that of MLCCs sintered by the TSS method with a low heating rate of 4 °C min⁻¹, the interface bonding between internal metal electrodes and dielectric layers of MLCCs sintered via the TSS method with the fast heating rate is dramatically improved. Nearly no pores between the internal electrodes and dielectric layers or discontinuity of internal electrodes is observed. A high energy density of 8.13 J cm⁻³ and an ultrahigh efficiency of 95% are achieved under an applied electric field of 750 kV cm⁻¹ in the MLCC sintered via the TSS method with the fast heating rate. Furthermore, this TSS method sintered MLCC exhibits a wide usage temperature range up to 170 °C, with a variation of discharge energy density less than 7%. Notably, it maintains a high efficiency over 91% even at a high temperature of 170 °C. These features demonstrate that MLCCs sintered via the TSS method with the fast heating rate are promising candidates for high-temperature energy-storage applications.