High energy density dielectrics in lead-free Bi0.5Na0.5TiO3–NaNbO3–Ba(Zr0.2Ti0.8)O3 ternary system with wide operating temperature

Abstract

The 0.6Bi0.5Na0.5TiO3–(0.4 − x)NaNbO3–xBa(Zr0.2Ti0.8)O3 (BNT–NN–BZT) ceramics were developed for application as high energy density capacitor by conventional solid-state reaction method, and their structure, dielectric and ferroelectric properties were investigated in detail. When BZT was introduced into the system, the crystal structure changed from tetragonal to pseudocubic. Temperature dependent dielectric permittivity showed a broad maximum in these pseudocubic ceramics, exhibitting distinct relaxor feature. The relaxor behavior was evaluated by modified Curie–Weiss and confirmed to be enhanced with increasing BZT content. Benefited from the relaxor feature, its dielectric constant and dielectric temperature stability were largely improved. The remanent polarization (Pr) and coercive electric field (Ec) decreased with high BZT content and the maximum polarization (Pm) improved as shown in ferroelectric hysteresis loops (P–E loops). The energy storage property was also improved with increasing BZT, the optimized energy storage property was obtained in x = 0.20 sample with W = 1.69 J/cm3 at 17.5 kV/mm, which was superior to many other ferroelectric relaxors, indicating that BNT–NN–BZT ceramics were promising candidates for temperature stable energy storage applications.