Giant Electric Energy Density in Epitaxial Lead‐Free Thin Films with Coexistence of Ferroelectrics and Antiferroelectrics

Abstract

lowest energy density. [4][5][6] To improve this, much attention has been particularly paid to antiferroelectric ceramics such as PZ, [ 7,8 ] PLZT, [ 9,10 ] PZN-PMN-PT, [ 4 ] PLZST, [ 4 ] etc., since they normally have higher energy density than ferroelectric and paraelectric ceramics at comparable electric fi eld. [ 2 ] The energy density in bulk ceramics is usually less than 1 J cm −3 because of the limitation of low dielectric breakdown strength (<100 kV cm −1 ). [ 11,12 ] With the development of high-quality thin fi lms by sol-gel, pulsed laser deposition (PLD), molecular beam epitaxy, etc., large energy density, mainly in lead-based antiferroelectric thin fi lms, has been achieved due to the higher dielectric breakdown strength (>500 kV cm −1 ). [ 3,9,13,14 ] For example, a high energy density of 53 J cm −3 at 3500 kV cm −1 was obtained in relaxor antiferroelectric (Pb 0.92 La 0.08 )(Zr 0.9 Ti 0.05 ) O 3 sol-gel thin fi lm. [ 9 ] However, widespread applications of lead-based materials are prohibited due to the toxicity of lead. As a lead-free dielectric material, poly(vinylidene fl uoride) (PVDF)-based polymer was also widely studied and a high energy density of 27 J cm −3 at 8000 kV cm −1 was reported. [ 1,4 ] However, its lifetime and reliability are seriously impaired at the maximum operating temperature (typically less than 85 °C), seriously limiting its applications as capacitors.Ferroelectrics/antiferroelectrics with high dielectric breakdown strength have the potential to store a great amount of electrical energy, attractive for many modern applications in electronic devices and systems. Here, it is demonstrated that a giant electric energy density (154 J cm −3 , three times the highest value of lead-based systems and fi ve times the value of the best dielectric/ ferroelectric polymer), together with the excellent fatigue-free property, good thermal stability, and high effi ciency, is realized in pulsed laser deposited (Bi 1/2 Na 1/2 ) 0.9118 La 0.02 Ba 0.0582 (Ti 0.97 Zr 0.03 )O 3 (BNLBTZ) epitaxial lead-free relaxor thin fi lms with the coexistence of ferroelectric (FE) and antiferroelectric (AFE) phases. This is endowed by high epitaxial quality, great relaxor dispersion, and the coexistence of the FE/AFE phases near the morphotropic phase boundary. The giant energy storage effect of the BNLBTZ lead-free relaxor thin fi lms may make a great impact on the modern energy storage technology.

Strongly enhanced dielectric and energy storage properties in lead-free perovskite titanate thin films by alloying

“…W of the BTO100 film is 5.6 J cm comparable to the highest reported W values from lead-based materials (Fig. 7) [76]. Compared with the BNLBTZ film, our films have simple compositions which means they are easier to process.…”

“…Dielectric capacitors are a promising technology for energy storage devices in high-power applications because of their high-power density, fast charge/discharge time (< 1 μs), low cost, and high thermal and mechanical stability [72][73][74][75][76]. The energy density (W) of a dielectric material is given by…”

Enhanced Energy Storage with Polar Vortices in Ferroelectric Nanocomposites

“…In high-quality ferroelectric/antiferroelectric thin films the energy storage density is much higher than that of ceramics due to the enhanced dielectric breakdown strength. For example, a very high energy storage density of 154 J/cm 3 at 218MV/m was achieved in the antiferroelectric film (Bi 1/2 Na 1/2 ) 0.9118 La 0.02 Ba 0.0582 (Ti 0.97 Zr 0.03 )O 3 [2], and recently Bin Xu et al [3] predicted via first principle calculations an energy storage density of 100-150 J/cm 3 in the lead free Bi 1−x R x FeO 3 system. However, from a practical point of view, the energy density is determined by the processing method and quality of the film as failure is often driven by flaws.…”

Dynamics of antipolar distortions

“…For instance, the Pnma state in ABO 3 perovskites is known to possess antipolar motions of its A cations and recent studies found that it can also adopt the double polarization-vs.-electric field hysteresis loop in some materials 13,14 that is characteristics of antiferroelectrics 15 -therefore suggesting that Pnma states in some perovskites can hold promise towards the design of energy storage devices with high energy densities and efficiencies. [16][17][18][19][20][21][22] Interestingly, all the aforementioned works on trilinear energetic couplings have been aimed at revealing and understanding resulting static properties. In other words, the effect of these original trilinear couplings on dynamics have been left out so far and are thus basically unknown, to the best of our knowledge.…”