Capturing Carriers and Driving Depolarization by Defect Engineering for Dielectric Energy Storage

Abstract

The inevitable defect carriers in dielectric capacitors are generally considered to depress the polarization and breakdown strength, which decreases energy storage performances. Distinctive from the traditional aims of reducing defects as much as possible, this work designs (FeTi ′ – Vo ••)• and (FeTi ″ – Vo ••) defect dipoles by oxygen vacancy defect engineering in acceptor doped Sr2Bi4Ti(5–x)Fe x O18 layered perovskite films with n-type leakage conductance. It is shown that oxygen vacancies effectively capture electrons (carriers) in n-type dielectrics to enhance the breakdown strength. Meanwhile, defect dipoles provide a driving field for depolarization to engineer the generation energy of domains and the domain wall energy, which effectively lowers the residual polarization P r but not at the expense of the maximum polarization P max as relaxor ferroelectric regulations. Such defect engineering effectively breaks through the limitation, in which the energy storage density suffers from the trade-off relationship between polarization and breakdown strength. The Sr2Bi4Ti4.92Fe0.08O18 film with the proper oxygen vacancy content achieves a high energy density of 110.5 J/cm3 and efficiency of 70.0% at a high breakdown strength of 3915 kV/cm. This work explores an alternative way for breakthroughs possible in the intrinsic trade-off relationship to regulate dielectric energy storage by defect engineering.

Enhancing Comprehensive Energy Storage Properties in Tungsten Bronze Sr0.53Ba0.47Nb2O6-Based Lead-free Ceramics by B-Site Doping and Relaxor Tuning

“…In the last decade, compared with the normal FE and antiFE (AFE) materials, unceasing efforts focusing on ceramic capacitor materials with relaxor FE (RFE) behavior have been made, especially on ABO 3 perovskite materials. − Taking (Bi, K, Na)­TiO 3 -, NaNbO 3 -, and BiFeO 3 -based lead-free ceramics as examples, a breakthrough W r of above 7 J/cm 3 accompanied by η above 69% could be obtained via fine composition control. − After doping the second counterparts, an obvious relaxor behavior has been identified, which has been derived from the response of polar nanoregions (PNRs) to an alternating electric field. Specifically, accompanied by the evolution of microdomain to nanosized domains, RFE ceramics could ensure a large Δ P ( P m – P r ) and a moderate E B .…”

Synergistic Optimization in a 0.90BaTiO3–0.08Bi(Ni0.5Zr0.5)O3–0.02BiFeO3 Thin Film with High Breakdown Strength and Energy Density

“…In addition, defined as a large spontaneous polarization material, the increase of BF content enhances P max of the material to some extent. Figure compares other systems of ceramic thin-film energy storage materials with this work. ,,,,,− Owing to its large BDS and enhancive polarization, the 0.90BT–0.08BNZ–0.02BF thin film possesses higher W rec of 114.3 J cm –3 and shows great advantages in pulse power applications.…”

“…• provide a depolarization field that effectively reduces P r without harming P max . 32 For the Bi 3.15 Nd 0.85 Ti 2.8 Zr 0.2 O 12 −0.09BiFeO 3 system, the substitution of Fe ions for Ti 4+ enlarges the cell volume and produces the tensile chemical pressure, which results in the enhancement of polarization. 33 Therefore, nanoscale crystalline regions and BiFeO 3 introduced into amorphous films are beneficial for improving (P max −P r ) value energy storage performance of amorphous films.…”

“…On the other hand, BiFeO 3 is used for modifying polarization performance via defect engineering. In Sr 2 Bi 4 Ti (5– x ) Fe x O 18 thin-film capacitors, defect dipoles (Fe Ti ″ -V O ·· ) and (Fe Ti ′ -V O ·· ) · provide a depolarization field that effectively reduces P r without harming P max . For the Bi 3.15 Nd 0.85 Ti 2.8 Zr 0.2 O 12 –0.09BiFeO 3 system, the substitution of Fe ions for Ti 4+ enlarges the cell volume and produces the tensile chemical pressure, which results in the enhancement of polarization .…”

Polarization Rotation Control Domain Dynamic Response Modulates Piezoelectric Properties of Lead‐Free Thin Films

“…[39] As shown in Figure 2c, the O1s spectra of all samples can be distinguished into three parts: where the peaks at 528.8 eV are related to lattice oxygen (O L ) and the peaks at 530.8 eV reflect the chemisorbed oxygen, which is a typical feature of the existence of oxygen vacancies (O C ); and the pink peak at 533.4 eV might be induced via the OHgroup (O H ). [37] The ratio of different types of oxygen content in the thin films with the three selective orientations are presented in Figure 2d. Compared to approximately half of the oxygen vacancy content in randomly oriented thin films (Figure S2a, Supporting Information), it is clear that orientation modulation does have a significant effect on reducing the oxygen vacancies content of BNT-ST-BFMT thin films.…”