Aliovalent Doping Engineering for A- and B-Sites with Multiple Regulatory Mechanisms: A Strategy to Improve Energy Storage Properties of Sr_0.7Bi_0.2TiO₃-Based Lead-Free Relaxor Ferroelectric Ceramics

Abstract

Sr 0.7 Bi 0.2 TiO 3 (SBT) is a promising pulse energy storage material due to minor hysteresis, but its low maximum polarization (P max ) is bad for energy storage. K + −Bi 3+ defect pairs were introduced into the A-site of SBT to obtain Sr 0.35 Bi 0.35 K 0.25 TiO 3 (SBKT) with larger P max . Through firstprinciples calculations, we determined that the introduction of defect pairs destroys the paraelectric order phase and increases local polarization, resulting in more and larger polar nanoregion (PNR) formation. On this basis, doping NaNbO 3 (NN) in A-and B-sites of SBKT increases the cationic disorder and ferroelectric destabilization, further destroying the long-range order structure and forming more PNRs with smaller sizes. This enhances relaxation and decreases remnant polarization, and the broadened dielectric peak enables 0.85SBKT−0.15NN to meet the X7R specification. Furthermore, the decreased grain size and oxygen vacancy, increased thermal conductivity, and weakened local electric field (simulated by COMSOL) increase the dielectric breakdown strength (BDS). As a result, 0.95SBKT−0.05NN exhibits a high energy storage density (W) of 2.45 J/cm 3 with a high efficiency of 93.1%, a high pulsed discharge energy density of 2.1 J/cm 3 , and a high power density of 54.1 MW/cm 3 at 220 kV/cm. The energy storage properties show excellent stability of temperature (−55 to 150 °C), frequency (10−500 Hz), and cycling (10 5 cycles). Notably, for the pulse charge−discharge properties, 0.95SBKT−0.05NN shows great fatigue resistance during 10 5 cycles under 25 and 150 °C, accompanied by excellent thermal stability. Moreover, the BDS and P max of 0.95SBKT−0.05NN sintered in O 2 further enhance. A higher W of 2.92 J/cm 3 with a high efficiency of 89% at 250 kV/cm is achieved. Therefore, 0.95SBKT−0.05NN shows great application potential for pulse energy storage. In this work, we provide a novel strategy and systematic in-depth study for improving the energy storage properties of SBT.

Discovery of electric devil’s staircase in perovskite antiferroelectric

“…Despite many significant progresses have been recently achieved in obtaining high energy storage density for bulk ceramics, further efforts should be used to improve the thermal stability for practical application. Figure 4D summarizes recent studies with considering thermal stability for representative lead-free and lead-based ceramics (including bulk ceramics and multilayer ceramic capacitors, see detailed compositions in table S1) (29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40). It can be seen that, at room temperature, the highest W rec = 7.7 J/cm 3 was achieved at a medium electric field of 310 kV/cm for PLZS, which is superior to all other systems.…”

Fantastic Energy Storage Performances and Excellent Stability in BiFeO3–SrTiO3-Based Relaxor Ferroelectric Ceramics

“…As shown, a slight decrease in P max and a noticeable increase in P r can be observed with the increasing frequency, which might be related to the decrease of the PNR dynamics at high frequencies. 18,48 Nevertheless, both W rec and η change slightly from 3.07 to 2.82 J/cm 3 and from 87.43% to 80.86%, demonstrating that the 0.7(BF-ST)-0.3SBT ceramic shows outstanding frequency stability. Furthermore, the P−E loops of the 0.7(BF-ST)-0.3SBT ceramic keep a similar form with almost unchanged P max and P r even after 3 × 10 5 cycles, resulting in a nearly fatigue-free W rec and η with a tiny variation below 2.4%, as shown in Figure 7d.…”

“…In this study, a typical relaxor ferroelectric Sr 0.7 Bi 0.2 TiO 3 with perovskite structure was incorporated into the 0.6BiFeO 3 − 0.4SrTiO 3 ferroelectric solid solution, which possesses strong relaxation characters with low P r and high P max and has been widely employed to tailor the ESP of a lot of energy storage materials. 17,18 Doping effects of SBT on the microstructure, dielectric, ferroelectric and ESP of the BF-ST ceramic are investigated systematically. The experimental results reveal the introduction of SBT to the BF-ST ceramic successfully boosts its ESP through inducing PNRs and inhibiting grain growth, giving a noteworthy W rec (∼5.61 J/cm 3 ) and excellent η (∼86.76%).…”

Achieving Ultrahigh Energy-Storage Density with Excellent Thermal Stability in Sr0.7Bi0.2TiO3-Based Relaxors via Polarization Behavior Modulation

“…The achieved W rec value is the record-high in SBT-based (SBT content >50%) systems up to now. The comparisons of W rec , η, and P max values with some SBT-based ceramics are given in Figure e. ,,− It is observed that SBT-based ceramics usually possess high η due to the intrinsic relaxor characteristic. However, the W rec value is restricted by the limited P max value.…”

“…In general, the W rec of 3.6–4.1 J/cm 3 and a high η above 88% can be achieved from −50 to 200 °C. Figure c exhibits the comparison of W rec between the x = 0.44 sample and other representative recently reported SBT-based ceramics. ,,− Detailed information is shown in Table S2. It is observed that the current sample demonstrates superiorities both in high W rec value and wide operating temperature range.…”