Enhancement of Charge-Discharge Properties and Temperature Stability of (Ba_0.975Na_0.05)Ti_0.99Nb_0.01O₃ Ceramic by Doping High-Entropy Oxide

Abstract

A bidirectional optimization strategy was adopted to fabricate (1-x)(Ba0.975Na0.05)Ti0.99Nb0.01O3)-xBi(Zn0.2Mg0.2Al0.2Sn0.2Zr0.2)O3(abbreviated as (1-x)BNNT-xBZMASZ, x = 0.02–0.10) ceramics, aimed to improve the energy storage performance. X-ray diffraction results revealed that Bi2+ cations entered the A site and the multiple cations occupied the B site of BNNT, thereby decreased the remnant polarization intensity and refined the hysteresis loop. Scanning electron microscopy images showed uniform morphologies with clear grain boundaries of the ceramics, and the average size decreased with x increasing. The substitution of multiple cations at the B-site induced the splitting of macroscopic ferroelectric domains into smaller polar nanodomains, leading to the formation of high-dynamic polar nanoregions and accelerating the transition from BNNT to relaxor ferroelectrics, thus improving relaxation properties of the material. The excellent energy storage density (Wrec ∼ 2.80 J cm−3) and efficiency (∼90.0%) can be obtained under 200 kV cm−1. Moreover, the discharge-charge testing revealed excellent current density (∼589.5 A cm−2), high power density (∼20.63 MW cm−2), and extremely short discharge time (t0.9 ∼ 50.4 ns), along with exceptional temperature stability and cycling stability under the equivalent electric field of 120 kV cm−1. The 0.92BNNT-0.08BZMASZ ceramic offers a new approach to the design and an improvement of pulsed dielectric capacitor materials.