The impact of defects on the performance of piezoelectric materials has been a topic of considerable debate, due to the competing actions of the deteriorating effect of the defects themselves on the ceramic resistance and the positive effect on the piezoelectric performance resulting from the defect polarization. In order to probe its combined influence on piezoelectric properties, here, we designed BiFeO3 (BF)-based ceramics with different defect concentrations. It has been demonstrated that the incorporation of an appropriate concentration of defects into ceramics can effectively enhance their piezoelectric properties while maintaining their insulating properties. During the polarization process, both the intrinsic polarization and defect dipoles are oriented along the direction of the electric field. This occurs in the presence of a high temperature environment as well as an applied electric field, which results in a complementary enhancement of the macroscopic ferro- and piezoelectric properties. Consequently, the piezoelectric performance of BF–BT–BKT ceramics is achieved (d33 = 203 ± 5 pC/N, TC = 502 °C, kp = 33.05%). This work provides a framework for understanding the intrinsic structural mechanism of bismuth ferrate.
Xiaohui Tang,Hongjun Zhang,Fangzhe Li,Dongliang Wang,Yong Huang,Hua Ke
Dielectric capacitors play an increasingly important role in power systems because of their fast charging and discharging speed. Applications are usually limited due to the low W rec . We design materials with high values of Δ P ( P max - P r ) and recoverable energy storage density( W rec ) from the high entropy perspective. Two single phases with a large Curie temperature T c difference have been selected, which leads to the enlarged entropy. The ceramics (Bi 0.85 Nd 0.1 Sm 0.05 ) 1- x Ba x )(Fe 1- x Ti x )O 3 (BNSBFT x ) are prepared by the solid-state reaction. As x increases, the corresponding configuration entropy( S config ) goes from 1.4 R to 1.52 R. The increased entropy destroys the long-range order, accompanied by the reduced remanent polarization( P r ) and the improved W rec . The W rec of BNSBFT 0.5 ceramics reaches 4.9 J/cm 3 at a low field of 250 kV/cm. Both temperature change(∼ 0.5% from 30 °C to 140 °C) and frequency variation(∼ 4.8% from 1 Hz∼50 Hz) in W rec show excellent stability.
The development of ceramic capacitors with superior energy storage capabilities (>5 J/cm 3 ) under moderate electric fields (300–500 kV/cm) is essential for their practical integration into advanced electronic devices. Here, (1- x )(0.67BiFeO 3 -0.33BaTiO 3 )- x Na(Ta 0.5 Nb 0.5 )O 3 ( x = 0–0.25) ceramics are successfully synthesized, demonstrating exceptional energy storage performance. Specifically, the appropriate introduction of the Na(Ta 0.5 Nb 0.5 )O 3 can disrupt the long-range ordered structure in the ferroelectric samples and suppress the octahedral distortion, promoting the formation of polar nanoregions and reducing the remanent polarization. Meanwhile, a large bandgap and conductive activation energy endow it with a high breakdown strength. As a result, a high recoverable energy storage density of 6.44 J/cm 3 and a high energy storage efficiency of 87 % are achieved in the as-synthesized 0.8BFBT-0.2NTN samples under 440 kV/cm, with excellent frequency stability, temperature stability, and fatigue stability. This work presents a viable strategy for improving the energy storage properties of BiFeO 3 -based ceramics under moderate electric fields, offering significant potential for next-generation energy storage applications.
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