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With the increasing demand for portable electronics, power electronics and other devices, energy storage materials with high power density and large energy storage density are becoming more and more important. BiFeO3-BaTiO3 lead-free ferroelectric ceramics are deemed as a potential lead-free energy storage material due to their high spontaneous polarization and high Curie temperature. However, high remanent polarization has become a serious obstacle to its practical application. In this work, 0.67Bi(1-x)SmxFeO3-0.33BaTiO3 (BSxF-BT, 0 ≤ x ≤ 0.10) was prepared by the conventional solid phase sintering method. The phase transforms from rhombohedral to pseudocubic, and the dielectric and electrical data reveal that relaxor ferroelectrics are favorable for achieving the small size polar nanoregions and enhanced relaxation behavior. Due to enhanced relaxation behavior by doping Sm3+, the recoverable energy storage density (Wrec) reaches 1.99 J/cm3, and the energy storage efficiency (η) is 57% at a low electric field (190 kV/cm), which is higher than the undoped ceramic (Wrec = 0.272 J/cm3 and η = 26%). This work also puts forward the concept of Ergodic relaxor ferroelectrics and Non-ergodic relaxor ferroelectrics to explain the improvement of energy storage performance. [ABSTRACT FROM AUTHOR] more...

Due to the self-supplied energy requirements of wearable electronic devices, flexible piezoelectric energy harvesters (FPEHs) that can convert the vibration energy in the environment into electrical energy have received widespread attention in recent years. The key to increasing the power generation capacity of FPEHs is to increase the piezoelectric charge constant d33 while reducing the internal resistance, which is still a huge challenge for ceramic/polymer composites. In this work, a synergistic effect is used to construct FPEHs with high power generating capacity. On the one hand, a highly electroactive 0.2Pb(Zn1/3Nb2/3)O3–0.8Pb(Zr1/2Ti1/2)O3 (PZN–PZT) ceramic skeleton is constructed through a freeze-casting method to greatly increase the d33 of a PDMS based composite. On the other hand, multi-walled carbon nanotubes (MW-CNTs) are introduced as a bridging phase to reduce the internal resistance of the composite. The 2–2 type PZN–PZT/MW-CNTs/PDMS piezocomposite prepared using this strategy has a d33 as high as 144 pC N−1, which is significantly better than those of previously reported composites. The FPEH with dimensions of 1.5 × 1.5 × 0.1 cm3 can light 22 LEDs through the rectifier circuit without any storage units, showing an important application prospect for self-supply of energy in wearable electronic devices. [ABSTRACT FROM AUTHOR] more...