Giant energy density and high efficiency achieved in bismuth ferrite-based film capacitors via domain engineering

Abstract

Developing high-performance film dielectrics for capacitive energy storage has been a great challenge for modern electrical devices. Despite good results obtained in lead titanate-based dielectrics, lead-free alternatives are strongly desirable due to environmental concerns. Here we demonstrate that giant energy densities of ~70 J cm−3, together with high efficiency as well as excellent cycling and thermal stability, can be achieved in lead-free bismuth ferrite-strontium titanate solid-solution films through domain engineering. It is revealed that the incorporation of strontium titanate transforms the ferroelectric micro-domains of bismuth ferrite into highly-dynamic polar nano-regions, resulting in a ferroelectric to relaxor-ferroelectric transition with concurrently improved energy density and efficiency. Additionally, the introduction of strontium titanate greatly improves the electrical insulation and breakdown strength of the films by suppressing the formation of oxygen vacancies. This work opens up a feasible and propagable route, i.e., domain engineering, to systematically develop new lead-free dielectrics for energy storage.

Preparation and characterization of flexible, free‐standing, and easy‐fabricating BaTiO3‐P(VDF‐CTFE) dielectric nanocomposite

“…The U of a capacitor is directly determined by the dielectrics used, which can be expressed as: where E is the applied electric field, and D is the electric displacement of the dielectric under the corresponding electric field . Therefore, the development of dielectric materials with improved energy densities is required for the miniaturization of electrical power systems . In this regard, relaxor‐ferroelectric (REF) materials have been studied due to their large saturation polarization ( P s ), small remnant polarization ( P r ) and high energy efficiency ( η ) .…”

“…Therefore, the development of dielectric materials with improved energy densities is required for the miniaturization of electrical power systems . In this regard, relaxor‐ferroelectric (REF) materials have been studied due to their large saturation polarization ( P s ), small remnant polarization ( P r ) and high energy efficiency ( η ) . To date, some promising RFE thin films were developed.…”

“…To date, some promising RFE thin films were developed. For example, U values of ~70 J/cm 3 in 0.4(BiFeO 3 )‐0.6(SrTiO 3 ) films and ~50 J/cm 3 in 0.6(Bi 0.5 Na 0.5 )TiO 3 ‐0.4Bi(Ni 0.5 Zr 0.5 )O 3 films have been reported. However, compare with thin films, the REF bulk ceramics bear low breakdown strengths ( E b ) due to the existence of pores and impurities, which lead to the decrease of energy density …”

High‐recoverable energy‐storage density and dielectric tunability in Eu3+‐doped NBT‐xSTO binary solid solution films

“…The epitaxial Ba 0.7 Ca 0.3 TiO 3 ‐BaZr 0.2 Ti 0.8 O 3 multilayer films magnetron sputtered on Nb‐doped SrTiO 3 (Nb:STO) substrates were reported to have a large W r of 52.4 J cm −3 with an efficiency equal to 72.3% . The excellent results: W r ~ 70 J cm −3 , and η ~ 70% were obtained in the epitaxial BiFeO 3 ‐SrTiO 3 solid solution films grown on Nb:STO single crystal substrates by using a pulsed laser deposition method . However, the high cost of Nb:STO single crystal substrates is an obstacle for their practical applications in large‐scale devices because of the special preparation processing.…”

Enhancements of dielectric and energy storage performances in lead‐free films with sandwich architecture

“…Zhang et al and Chen et al separately reported (Bi 1/2 Na 1/2 )TiO 3 ‐based films with P m values > 40 μC cm −2 and U e values > 25 J cm −3 . In our recent work, we demonstrated the BiFeO 3 (BFO)‐SrTiO 3 (STO) solid‐solution films that achieved high P m values of ~60 μC cm −2 and superior energy densities of ~70 J cm −3 . However, the volatility of Bi usually causes large concentrations of bismuth vacancies and oxygen vacancies, leading to electrically leaky nature of the Bi‐containing films .…”