Gradient-Structured Ceramics with High Energy Storage Performance and Excellent Stability.

Owing to the high power density, eco-friendly, and outstanding stability, the lead-free ceramics have attracted great interest in the fields of pulsed power systems. Nevertheless, the low energy storage density of such ceramics is undoubtedly a severe problem in practical applications. To overcome this limitation, the lead-free ceramics with gradient structures are designed and fabricated using the tape-casting method herein. By optimizing the composition and distribution of the gradient-structured ceramics, the energy storage density, and efficiency can be improved simultaneously. Under a moderate electric field of 320 kV cm-1 , the value of recoverable energy storage density (Wrec ) is higher than 4 J cm-3 , and the energy storage efficiency (η) is of ≥88% for 20-5-20 and 20-10-20. Furthermore, the gradient-structured ceramics of 20-10-0-10-20 and 20-15-0-15-20 possess high applied electric field, large maximum polarization, and small remnant polarization, which give rise to ultrahigh Wrec and η on the order of ≈6.5 J cm-3 and 89-90%, respectively. In addition, the energy storage density and efficiency also exhibit excellent stability over a broad range of frequencies, temperatures, and cycling numbers. This work provides an effective strategy for improving the energy storage capability of eco-friendly ceramics.

Synergistic Optimization of Energy Storage Density of PYN-Based Antiferroelectric Ceramics by Composition Design and Microstructure Engineering.

PbYb0.5 Nb0.5 O3 (PYN)-based ceramics, featured by their ultra-high phase-switching field and low sintering temperature (950 °C), are of great potential in exploiting dielectric ceramics with high energy storage density and low preparation cost. However, due to insufficient breakdown strength (BDS), their complete polarization-electric field (P-E) loops are difficult to be obtained. Here, to fully reveal their potential in energy storage, synergistic optimization strategy of composition design with Ba2+ substitution and microstructure engineering via hot-pressing (HP) are adopted in this work. With 2 mol% Ba2+ doping, a recoverable energy storage density (Wrec ) of 10.10 J cm-3 and a discharge energy density (Wdis ) of 8.51 J cm-3 can be obtained, supporting the superior current density (CD ) of 1391.97 A cm-2 and the outstanding power density (PD ) of 417.59 MW cm-2 . In situ characterization methods are utilized here to reveal the unique movement of the B-site ions of PYN-based ceramics under electric field, which is the key factor of the ultra-high phase-switching field. It is also confirmed that microstructure engineering can refine the grain of ceramics and improve BDS. This work strongly demonstrates the potential of PYN-based ceramics in energy storage field and plays a guiding role in the follow-up research.

High Piezoelectricity in Eco-Friendly NaNbO3-Based Ferroelectric Relaxor Ceramics via Phase and Domain Engineering.

To meet the requirements of environmental friendliness, high-performance lead-free piezoelectric materials have become important materials for next-generation electronic devices. Here, lead-free and potassium-free NaNbO3 (NN)-based ceramics with high piezoelectric (d33 = 361 ± 10 pC/N) and dielectric (εr = 4500) properties were obtained by tolerant preparation techniques. The excellent piezoelectric and dielectric properties can be attributed to the relaxor morphotropic phase boundaries (R-MPB) and coexisting domain regions, which are beneficial in lowering the free energy and greatly improving the dielectric response and domain switching capability. Furthermore, the d33 of NaNbO3-10Ba(Ti0.7Sn0.3)O3-1.5NaSbO3 (NN-10BTS-1.5NS) ceramics can be maintained at 350 pC/N over the range of 25-80 °C with a change rate of less than 10%, exhibiting excellent temperature stability. Based on a series of in situ characterizations, the variations of the phase and domain structures of NN-based relaxor piezoelectric ceramics with temperature are clearly demonstrated. This work not only proposes new materials for sensors and actuators but also provides an excellent strategy for designing high-performance piezoelectric ceramics through phase and domain engineering.

Tunable Domain Switching Features of Incommensurate Antiferroelectric Ceramics Realizing Excellent Energy Storage Properties.

An incommensurate modulated antiferroelectric phase is a key part of ideal candidate materials for the next generation of dielectric ceramics with excellent energy storage properties. However, there is less research carried out when considering its relatively low polarization response. Here, the incommensurate phase is modulated by stabilizing the antiferroelectric phase and the energy storage performance of the incommensurate phase under ultrahigh electric field is studied. The tape-casting method is applied to construct dense and thin ceramics. La3+ doping induces a room-temperature incommensurate antiferroelectric orthorhombic matrix. With little Cd2+ , the extremely superior energy storage performances arose as follows: when 0.03, the recoverable energy storage density reaches ≈19.3 J cm-3 , accompanying an ultrahigh energy storage efficiency of ≈91% (870 kV cm-1 ); also, a giant discharge energy density of ≈15.4 J cm-3 emerges during actual operation. In situ observations demonstrate that these superior energy storage properties originate from the phase transition from the incommensurate antiferroelectric orthorhombic phase to the induced rhombohedral relaxor ferroelectric one. The adjustable incommensurate period affects the depolarization response. The revealed phase-transition mechanism enriches the existing antiferroelectric-ferroelectric transition. Attention to the incommensurate phase can provide a reference for the selection of the next generation of high-performance antiferroelectric materials.