Enhancing Comprehensive Energy Storage Properties in Tungsten Bronze Sr_0.53Ba_0.47Nb₂O₆-Based Lead-free Ceramics by B-Site Doping and Relaxor Tuning

Abstract

Dielectric ceramics with relaxor characteristics are promising candidates to meet the demand for capacitors of next-generation pulse devices. Herein, a lead-free Sb-modified (Sr0.515Ba0.47Gd0.01) (Nb1.9‑x Ta0.1Sb x )­O6 (SBGNT-based) tungsten bronze ceramic is designed and fabricated for high-density energy storage capacitors. Using a B-site engineering strategy to enhance the relaxor characteristics, Sb incorporation could induce the structural distortion of the polar unit BO6 and order–disorder distribution of B-site cations as well as the modulation of polarization in the SBGNT-based tungsten bronze ceramic. More importantly, benefiting from the effective inhibition of abnormal growth of non-equiaxed grains, Sb introduction into SBGNT-based ceramics could effectively suppress the conductivity and leakage current density, enhancing the breakdown strength, as proved by the electrical impedance spectra. Consequently, a remarkable comprehensive performance via balancing recoverable energy density (∼3.26 J/cm3) and efficiency (91.95%) is realized simultaneously at 380 kV/cm, which surpasses that of the pristine sample without the Sb dopant (2.75 J/cm3 and 80.5%, respectively). The corresponding ceramics display superior stability in terms of fatigue (105 cycles), frequency (1∼200 Hz), and temperature (20∼140 °C). Further charge–discharge analysis indicates that a high power density (89.57 MW/cm3) and an impressive current density (1194.27 A/cm2) at 150 kV/cm are achieved simultaneously. All of the results demonstrate that the tungsten bronze relaxors are indeed gratifying lead-free candidate materials for dielectric energy storage applications.

Ultrahigh Polarization Response along Large Energy Storage Properties in BiFeO3–BaTiO3-Based Relaxor Ferroelectric Ceramics under Low Electric Field

“…Note that the relatively high W rec can be realized under a low E of 160 kV/cm, which is mostly resulted from the large polarization discrepancy Δ P (Δ P = P m – P r ) of ∼58.5 μC/cm 2 . This Δ P is at a higher value in dielectric ceramics that have been previously documented. − The ultrahigh Δ P value should be owing to the large lattice distortions in the perovskite structure. Consider that the ferroelectric polarization mostly results from the orbital hybridization of Bi 6p and O 2p in BF-based systems.…”

“…It can be widely recognized that the compositional disorder of A- and/or B-sites in BF–BT-based systems is the majority method to boost ESP by regulating relaxor behavior, nanodomain engineering, and decreasing grain size, ,, as schematized in Figure . To design BF–BT-based ceramics for application in energy storage device with a low electric field, here, a multiscale optimization strategy is proposed via a local compositional disorder with a B-rich content and nanodomain engineering by introducing the Sr 0.7 Bi 0.2 Ca 0.1 TiO 3 (SBCT) into 0.67BF–0.33BT ceramics.…”

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 ]…”

“…Prior research has established that the ion doping modulated regularity of ferroelectric and relaxor behavior in TTBS ceramics, which is primarily a result of cation occupancy and structural distortion. [ 25–31 ] In accordance with the crystal‐chemical framework, a small A‐site average ion radius causes a reduction in OBO bond length and benefits the improvement of relaxor properties. [ 32 ] Meanwhile, the weakened BO bonding, local structural fluctuation or distortion, and order–disorder distribution all support the modification of the B‐site cation to improve relaxor behavior.…”