Novel lead-free KNN-based ceramic with giant energy storage density, ultra-high efficiency and excellent thermal stability via relaxor strategy

Abstract

(1-x)(0.9 K0.5Na0.5NbO3-0.1Ba0.4Sr0.6TiO3)-xBi(Zn0.5Zr0.5)O3 ceramics (abbreviated as (1-x)KNNBST-xBZZ, x = 0, 0.05, 0.10, 0.15, 0.20) were synthesized using the solid-state reaction method and their structure and electrical characteristics, including dielectric and ferroelectric properties, were systematically investigated. The incorporation of Bi/Zn/Zr (BZZ) elements into the KNNBST system results in a substantial increase in volume density, a dominant cubic crystal structure, and enhanced relaxor behaviour. Consequently, these modifications have led to superior energy storage performance. The 0.9KNNBST-0.1BZZ ceramics shows excellent recoverable energy storage density (Wrec = 5.42 J/cm3), and ultra-high energy efficiency (η = 91.09 %) at 470 kV/cm. Moreover, the 0.9KNNBST-0.1BZZ ceramics exhibits favorable frequency stability (1–1000 Hz) and temperature stability (27–190 ℃). The outstanding energy storage characteristics of (1-x)KNNBST-xBZZ ceramics make them highly promising for advanced pulse power capacitors and various energy storage applications.