Achieving Ultrahigh Energy-Storage Density with Excellent Thermal Stability in Sr_0.7Bi_0.2TiO₃-Based Relaxors via Polarization Behavior Modulation

Abstract

Dielectric capacitors possessing the inherent superiorities of high power density and ultrafast charge–discharge speed make their utilization in energy-storage devices extremely propitious, although the relatively low recoverable energy-storage density (W rec) may impede their applications. In this work, unlike the mainstream approach of destroying long-range ferroelectric/antiferroelectric order and inducing relaxor properties to achieve a high W rec value, we have selected end members with a high polarization gene to promote the polarization behavior of the typical relaxor Sr0.7Bi0.2TiO3. Therefore, an ultrahigh W rec ∼ 8 J/cm3 and a superior efficiency (η) ∼ 91% are accomplished in the 0.98­[0.56­(Sr0.7Bi0.2)­TiO3-0.44­(Bi0.5Na0.5)­TiO3]-0.02 Bi­(Mg0.5Ti0.5)­O3 sample. The achieved W rec value is record high in Sr0.7Bi0.2TiO3-based systems as far as we know. The polarization-enhancement behavior can be explained by the phase field simulation results, phase content variance in X-ray diffraction Rietveld refinement, hardening trend in Raman spectroscopy, domain morphology, and local symmetry in transmission electron microscope analysis. Meanwhile, the ceramic possesses excellent thermal stability (ΔW rec < 12.7% and Δη < 10.4%, −50–200 °C), frequency (ΔW rec < 2.69% and Δη < 2.06%, 0.5–500 Hz), and fatigue-resistant stability (ΔW rec < 0.08% and Δη < 0.2%, up to 1 × 105 cycles). Accordingly, this work proposes a design idea to tailor the polarization behavior and energy-storage properties of typical relaxors.

Superior Energy Density Achieved in Unfilled Tungsten Bronze Ferroelectrics via Multiscale Regulation Strategy

“…As a result, W rec increases to 5.895 J cm −3 with an enhancement of 50.69%, and 𝜂 is also improved to 85.37%. The achievement of optimized composition of Sr 0.425 La 0.1 □ 0.05 Ba 0.425 Nb 1.4 Ta 0.6 O 6 can also be supported by a systematical investigation on the [17,18,[22][23][24][27][28][29][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53] structure and properties of Sr 0.425 La 0.1 □ 0.05 Ba 0.425 Nb 2−x Ta x O 6 ceramics with different Ta 5+ concentrations, which is summarized in Figures S1-S4 (Supporting Information). A comparison of the ESP of our SLBNT ceramics and previously reported lead-free bulk ceramics are illustrated in Figure 2e.…”

“…e) The comparison of W rec and η values of SLBNT and other recently reported lead‐free bulk ceramics. [ 17,18,22–24,27–29,38–53 ]…”

“…It is evident that the excellent overall performance of SLBNT ceramics leads the field in tetragonal tungsten bronze structure ferroelectric ceramics and can even be comparable with some state-of-the-art perovskite structure ceramics. [17,18,[22][23][24][27][28][29][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53] Figure 3a shows the X-ray diffractometer (XRD) patterns of SBN, SLBN, and SLBNT ceramics. All the patterns reveal pure tungsten bronze structure, indicating that the La 3+ and Ta 5+ successfully entered the SBN host lattice.…”

“…d) A comparison of E b , P m , W rec , and 𝜂 values between SBN, SLBN, and SLBNT ceramics. e) The comparison of W rec and 𝜂 values of SLBNT and other recently reported lead-free bulk ceramics [17,18,[22][23][24][27][28][29][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53].…”

Ultrahigh Energy-Storage Density of BaTiO3-Based Ceramics via the Interfacial Polarization Strategy

“…According to previous studies, the doping of Sr 0.7 Bi 0.2 TiO 3 (SBT) into the BT matrix can enhance relaxor properties. 21,22 This is because Sr vacancies can cause distortion of the oxygen octahedra and further lead to the relaxation motion of Ti 4+ ions. Both facts give SBT a low coercive field (E c ) and P r , favoring a high η.…”