High-temperature dielectric ceramics are in urgent demand due to the rapid development of numerous emerging applications. However, producing dielectric ceramics with favorable temperature, frequency and electric field stability is still a huge challenge. The construction of multi-phase coexistence material systems is an effective way to obtain stable dielectric and energy storage properties. In this work, NaNbO₃ (NN) modified 0.95Bi_0.5Na_0.5TiO₃–0.05SrZrO₃ (BNTSZ) ceramics ((1 − x)BNTSZ–xNN) are designed to achieve the coexistence of rhombohedral and tetragonal phases. The variation in the dielectric permittivity of the 0.8BNTSZ–0.2NN ceramic is less than ±15% over the temperature range from −55 °C to 545 °C, which is the reported record-high upper operating temperature, with a high room-temperature dielectric permittivity of 1170. The 0.8BNTSZ–0.2NN ceramic exhibits excellent frequency and electric field stability as well. Additionally, a large discharge energy density of 3.14 J cm⁻³ is obtained in the 0.85BNTSZ–0.15NN ceramic with an energy efficiency of 79% at a high temperature of 120 °C under 230 kV cm⁻¹, with the variation in the discharge energy density being less than ±4% in the temperature range from 25 °C to 180 °C under 120 kV cm⁻¹. All these features demonstrate that the (1 − x)BNTSZ–xNN ceramics are promising candidates for use at extremely high temperature in both dielectric and energy storage capacitor applications.

Piezoelectric materials provide high strain and large driving forces in actuators and can transform electrical energy into mechanical energy. Although they were discovered over 100 years ago, scientists are still searching for alternative lead-free piezoelectrics to reduce their environmental impact. Developing high-strain piezoelectric materials has been a long-term challenge, particularly challenging for the design of high-strain polycrystalline piezoelectrics containing no toxic lead element. In this work, we report one strategy to enhance the electrostrain via designing “heterostrain” through atomic-scale defect engineering and mesoscale domain engineering. We achieve an ultrahigh electrostrain of 2.3% at high temperature (220 °C) in lead-free polycrystalline ceramics, higher than all state-of-the-art piezoelectric materials, including lead-free and lead-based ceramics and single crystals. We demonstrate practical solutions for achieving high electrostrain in low-cost environmentally piezoelectric for various applications.

Two-dimensional monolayer materials, with thicknesses of up to several atoms, can be obtained from almost every layer-structured material. It is believed that the catalogs of known 2D materials are almost complete, with fewer new graphene-like materials being discovered. Here, we report 2D graphene-like monolayers from monoxides such as BeO, MgO, CaO, SrO, BaO, and rock-salt structured monochlorides such as LiCl, and NaCl using first-principle calculations. Two-dimensional materials containing d-orbital atoms such as HfO, CdO, and AgCl are predicted. Adopting the same strategy, 2D graphene-like monolayers from mononitrides such as scandium nitride (ScN) and monoselenides such as cadmium selenide (CdSe) are discovered. Stress engineering is found to help stabilize 2D monolayers, through canceling the imaginary frequency of phonon dispersion relation. These 2D monolayers show high dynamic, thermal, kinetic, and mechanic stabilities due to atomic hybridization, and electronic delocalization. Significance Since the discovery of graphene in 2004, 2D materials have sparked tremendous interest due to their fascinating optical, mechanical, and electronic properties, and their potential in catalysis, optoelectronic devices, energy storage, and conversion. After experimental and theoretical studies mainly focused on atomically thin nanomaterials with layered structures, the whole family of 2D materials is almost complete, and recently few new graphene-like materials were reported. Here, we report the discovery of graphene-like mononitrides, monoxides, monochlorides, and monoselenide monolayers, which have shown high dynamic, thermal, kinetic, and mechanic stabilities.