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In this work, the niobate-based borate glass-ceramic system K2O–Na2O–Nb2O5–B2O3 was proposed for the first time, in which the presence of alkali metal oxides not only tends to form ferroelectric crystalline phase to obtain high permittivity, but also optimizes the borate glass network structure to enhance the breakdown strength. The change of borate glass network structure and the influence on conductivity and carriers migrate is systematically discussed. The results show that the high breakdown performance is attributed to the transformation from [B∅2O−] triangle to [B∅4]- tetrahedron realizes the high extent of glass network polymerization, which effectively impedes carriers migration and reduces the conductivity. The high permittivity and low dielectric loss are obtained in the range of room temperature to 200 °C. Compared to other niobate-based glass-ceramics, the potassium sodium niobate borate glass-ceramic simultaneously achieve high discharge energy density, high power density and rapid discharge rate (∼14 ns).

Aiming at the problem that power density and energy density are difficult to obtain simultaneously under low field, a novel composition (1-x)Na0·5Bi0·5TiO3-xBaZn1/3Ta2/3O3((1-x)NBT-xBZT) was designed and fabricated via solid-state methods. With the addition of BZT, the crystal lattice, structural symmetry, grain size, and dense degree were all increased proved by XRD, Raman, and Archimedes drainage method et al. Because of the enhancement of relaxor behavior, the x=0.10 sample displayed a high permittivity er of 2871±15% and a low dielectric loss tan δ ≤ 0.025 in the wide temperature range of 60–400 oC. This ceramic also showed maximum recoverable energy density Wd (2.07 J/cm3) with high efficiency η (71.5%) under a low field of 150 kV/cm. Moreover, pulse discharge testing proved that this ceramic possessed both a significant discharge energy density WD (0.96 J/cm3) and a record high power density PD (108.54 MW/cm3). This work provided a promising material for high power and energy applications.

In this work, novel (1 [Formula: see text])(0.75Na[Formula: see text]Bi[Formula: see text]TiO3)-0.25Sr(Zr[Formula: see text]Sn[Formula: see text]Hf[Formula: see text]Ti[Formula: see text]Nb[Formula: see text])O3-[Formula: see text]NaNbO3 (NBT-SZSHTN-[Formula: see text]NN, [Formula: see text] = 0.1, 0.15, 0.2, 0.25) ceramics were fabricated. The influence of co-doping of NN and high entropy perovskite oxide (SZSHTN) on the phase structure, microstructure and dielectric properties of NBT-based lead-free ceramics was investigated. Dense microstructure with a grain size of [Formula: see text]5 [Formula: see text]m is observed. When [Formula: see text] = 0.25, a wide dielectric temperature stable range of −35.4–224.3[Formula: see text]C with a low temperature coefficient of capacitance of [Formula: see text] 10% is achieved, fulfilling the industry standard of Y9P specification. Furthermore, excellent energy storage performance with recoverable energy density of 2.4 J/cm3, discharge efficiency of 71%, power density of 25.495 MW/cm3 and discharge rate [Formula: see text] 200 ns are simultaneously obtained, which shows great potential for high temperature capacitor applications.

Dielectric capacitors with fast charge–discharge rate and high power density are drawing more attention in pulse power equipment field. In this work, bismuth-based high entropy compound (HEC), Bi(Zn0.2Mg0.2Al0.2Sn0.2Zr0.2)O3 (BZMASZ), was introduced into BaTiO3-Na0.5Bi0.5TiO3 (BT-NBT) matrix, in order to improve the comprehensive energy storage performance. The addition of BZMASZ induced phase transition from tetragonal phase to cubic phase, along with the enhancement of relaxor behavior and local nanodomains. The 0.1 BZMASZ modified 0.75BT-0.25NBT ceramics exhibited excellent recoverable energy density of Wrec ~ 3.74 J/cm3, high conversion efficiency of η ~ 82.2 % and superior temperature stability of ± 4.5 % from −30 to 200 °C. Combined with the high power density of PD ~ 34.76 MW/cm3 and rapid discharge rate of t0.9 ~ 67 ns, the x = 0.1 ceramics are considered to be the promising candidate for future wide-temperature pulse power applications.