Ultrahigh Energy-Storage Density of BaTiO₃-Based Ceramics via the Interfacial Polarization Strategy

Abstract

Lead-free dielectric capacitors are excellent candidates for pulsed power devices. However, their low breakdown strength (E b) strongly limits their energy-storage performance. In this study, Sr0.7Bi0.2TiO3 (SBT) and Bi­(Mg0.5Hf0.5)­O3 (BMH) were introduced into BaTiO3 (BT) ceramics to suppress interfacial polarization and modulate the microstructure. The results show that the introduction of SBT and BMH increases the band gap width, reduces the domain size, and, most importantly, successfully attenuates the interfacial polarization. Significantly enhanced E b values were obtained in (1 – x)­(0.65BaTiO3–0.35Sr0.7Bi0.2TiO3)–xBi­(Mg0.5Hf0.5)­O3 (BSBT–xBMH) ceramics. Meanwhile, the interfacial polarization was reduced to near zero in the sample with x = 0.10, achieving an ultrahigh E b (64 kV/mm) and a very large recoverable energy-storage density (W rec ≈ 9.13 J/cm3). In addition, the sample has excellent thermal stability (in line with EIA-X7R standards) and frequency stability. These properties indicate that the BSBT–0.10BMH ceramic holds promising potential for the application of pulsed power devices.

Excellent Energy Storage Performance Achieved in Sr(Sc0.5Nb0.5)O3-Doped Bi0.5Na0.5TiO3-Based Lead-Free Relaxor Ferroelectric Ceramics

“…Dielectric ceramic materials depend on the polarization and depolarization process driven by an electric field to attain energy storage . The special mechanism results in very fast charge/discharge rates.…”

“…Improving E b is also a crucial factor in optimizing the ESP of BNT-based ceramics. The E b of ceramic materials can be optimized by adjusting grain size, thickness, and dense property, as it is primarily related to their highly insulating grain boundaries. ,, Currently, enhancing E b can be achieved through grain refinement, , introducing high band gap ( E g ) compositions, , and optimizing thickness processes. , For example, Wang et al introduced BiScO 3 into BNST, which significantly diminished the grain size from 2.81 to 0.71 μm and boosted the E b from 185 to 480 kV·cm –1 . Lin et al introduced NaTaO 3 ( E g ∼ 4.1 eV) into the binary matrix BNT-BAT, which significantly reduced the grain size while increasing the E g , resulting in an improvement in E b from 240 to 420 kV·cm –1 .…”

“…Recently, many lead-free dielectric ceramic materials have been applied in energy storage systems due to their excellent thermal stability and good fatigue resistance, such as BaTiO 3 -based (BT), − NaNbO 3 -based (NN), − K 0.5 Na 0.5 NbO 3 -based (KNN), , and Bi 0.5 Na 0.5 TiO 3 -based (BNT). ,− Among them, BNT-based ceramics are considered the best candidates to replace Pb-based energy storage materials due to their high P max (>40 μC·cm –2 ) and relatively simple phase structure . According to previous reports, BNT exhibits a rhombohedral ( R , space group R 3 c ) phase structure below 255 °C, while the R phase in BNT gradually transforms into a tetragonal ( T , space group P 4 bm ) phase between 255 and 400 °C, forming a two-phase structure in which the R phase coexists with the T phase. − The R phase of BNT typically possesses high polarization, but there is a large polarization hysteresis under electric field action, causing BNT to exhibit square P – E hysteresis loops at ambient temperature. , In contrast, the T phase of BNT exhibits comparatively low polarization and high dynamic activity with small polarization hysteresis under electric field action .…”