Lead-free dielectric relaxor ferroelectric (RFE) ceramics are one of the promising materials for dielectric energy storage applications. However, the contradiction between high polarization and low hysteresis leads to interior energy storage performance, which greatly limits their applications in high/pulsed power systems. Here, we propose an effective strategy to significantly improve the energy storage properties of 0.94Bi_0.5Na_0.5TiO₃–0.06BaTiO₃ (0.94BNT–0.06BT) with a morphotropic phase boundary (MPB) composition by constructing multiscale polymorphic domains and local heterogeneous structures. The introduction of Nd(Mg_1/2Hf_1/2)O₃ (NMH) facilitates the formation of short-range ordered polar nanoregions (PNRs). Moreover, small amounts of nanodomains with high polarization are resulted from local heterogeneous structures with Bi- and Ti-rich regions. Multiscale polymorphic domains with the coexistence of rhombohedral/tetragonal (R+T) nanodomains and PNRs ensure both high polarization and low hysteresis, which is crucial for improving the energy storage performance. Furthermore, the excellent electrical insulation is resulted from the high insulation resistivity, grain size at the submicron scale and a wide band gap by NMH doping. Therefore, a high recoverable energy density (W_rec) of 7.82 J/cm³ with an ultrahigh efficiency (η) of 93.1% is realized in the designed BNT–BT–NMH ternary system because of both a large ΔP and high E_b. These findings, together with good temperature/frequency/cycling stability, indicate that the optimum composition ceramics are very promising materials for energy storage applications in high/pulsed power systems.

Aurivillius phase CaBi₂Nb₂O₉ (CBNO) ceramic with an ultrahigh Curie temperature (T_C) of ~934 °C shows huge potential in high-temperature piezoelectric applications. However, low piezoelectricity and poor electric insulation prevent its applications in high-temperature sensing. Here, we propose an effective multi-field coupling strategy to synergistically optimize piezoelectric property, electrical conduction behavior and temperature stability of CBNO ceramic. The constructed lattice stress and electric fields induced by introducing Li/Pr and Bi/Sc doping have great impacts on the lattice structure, microstructure, domain structure and defect chemistry. Therefore, a significant increase in piezoelectric activity (d₃₃) is resulted from the enhancement of polarization, the improvement of breakdown electric field and the production of nanoscale domains. In especial, the existence of pseudo-tetragonal phase boundary is helpful for the enhanced d₃₃. In the designed Ca_1–3x (Li_0.5Pr_0.5)_xBi_2+2xNb_2–xSc_xO₉ system, a high d₃₃ of ~18.2 pC/N accompanied by an ultrahigh T_C of ~938 °C is achieved in the x = 0.02 ceramic. This combined with high electrical resistivity (ρ~1.72 MΩ·cm at 600 °C) and nearly stable d₃₃ (up to 800 °C) indicates that it is a very promising piezoelectric material for high-temperature (up to 600 °C or higher) sensing applications.

Enhancing corrosion resistance of Mg-Zn alloys with high strength and low cost was critical for broadening their large-scale practical applications. Here we prepared solutionized, peak- and over-aged ZK60 alloys with and without microalloying Ca (0.26 wt.%) to explore the effects of nanoscale precipitates on their corrosion behavior in detail via experimental analyses and theoretical calculations. The results suggested the peak-aged ZK60 alloy with Ca addition showed improved corrosion resistance in comparison with the alloys without Ca, owing to the contribution of Ca on the refinement of precipitates and increase in their number density. Although the precipitates and Mg matrix formed micro-galvanic couples leading to dissolution, the fine and dense precipitates could generate “in-situ pinning” effect on the corrosion products, forming a spider-web-like structure and improving the corrosion inhibition ability accordingly. The pinning effect was closely related to the size and number density of precipitates. This study provided important insight into the design and development of advanced corrosion resistant Mg alloys.