(K,Na)NbO₃ (KNN)-based piezoelectric materials are candidates for replacing Pb-based materials. However, the piezoelectric properties of existing KNN-based single crystals are still inferior to those of Pb-based relaxor ferroelectric single crystals. Moreover, the piezoelectric response mechanism of KNN-based single crystals remains unclear. In this study, (Li,K,Na)(Nb,Sb,Ta)O₃:Mn (KNNLST:Mn) single crystals with an excellent piezoelectric coefficient d₃₃ of approximately 778 pC/N were prepared. Systematically studies of intrinsic and extrinsic piezoelectric responses have revealed that the high d₃₃ of KNNLST:Mn single crystals is related to the shear piezoelectric response of a single-domain state and irreversible domain wall motion of the engineering domains. Furthermore, the effect of the orthorhombic (O)-tetragonal (T) phase boundary on intrinsic and extrinsic piezoelectric response is systematically studied, and the impact mechanism is elucidated. The results indicate that a lower dielectric response and elastic constant limit the intrinsic shear piezoelectric response of KNNLST:Mn single crystals, and approaching the O–T phase boundary can enhance both intrinsic and extrinsic piezoelectric responses. This study improves our understanding of the structure-performance relationship in KNNbased single crystals and offers insights for optimizing piezoelectric properties in KNN-based materials.

Dielectric capacitors with ultrahigh power density and ultra-fast charge/discharge rate are highly desired in pulse power fields. Environmental-friendly AgNbO₃ family have been actively studied for its large polarization and antiferroelectric nature, which greatly boost the electric energy storage performance. However, high-quality AgNbO₃-based films are difficult to fabricate, leading to a low breakdown field E_b (<1.2 MV/cm) and consequently arising inferior energy storage performance. In this work, we propose an interface engineering strategy to mitigate the breakdown field issue. A Ag(Nb,Ta)O₃/BaTiO₃ bilayer film is proposed, where the BaTiO₃ layer acts as a p-type semiconductor while Ag(Nb,Ta)O₃ layer is n-type, together with the n-type LaNiO₃ buffer layer on the substrate, forming an n-p-n heterostructure. The n-p-n heterostructure elevates the potential barriers for charge transport, greatly reducing the leakage current. An extremely large breakdown field E_b~4.3 MV/cm is achieved, being the highest value up to date in the niobate system. A high recoverable energy density W_rec~62.3 J/cm³ and a decent efficiency η~72.3% are obtained, much superior to that of the Ag(Nb,Ta)O₃ monolayer film (W_rec~46.4 J/cm³ and η~80.3% at E_b~3.3 MV/cm). Our results indicate that interface engineering is an effective method to boost energy storage performance of dielectric film capacitors.

High-temperature piezoelectric materials with excellent piezoelectricity, low dielectric loss and large resistivity are highly desired for many industrial sectors such as aerospace, aircraft and nuclear power. Here a synergistic design strategy combining microstructural texture and chemical doping is employed to optimize CaBi₄Ti₄O₁₅ (CBT) ceramics with bismuth layer structure. High textured microstructure with an orientation factor of 80%–82% has been successfully achieved by the spark plasma sintering technique. Furthermore, by doping MnO₂, both advantages of hard doping and sintering aids are used to obtain the excellent electrical performance of d₃₃ = 27.3 pC/N, tanδ~0.1%, Q₃₁~2,307 and electrical resistivity ρ~6.5 × 10¹⁰ Ω·cm. Up to 600 ℃, the 0.2% (in mass) Mn doped CBT ceramics still exhibit high performance of d₃₃ = 26.4 pC/N, ρ~1.5 × 10⁶ Ω·cm and tanδ~15.8%, keeping at an applicable level, thus the upper-temperature limit for practical application of the CBT ceramics is greatly increased. This work paves a new way for developing and fabricating excellent high-temperature piezoelectric materials.

Due to its lead-free composition and a unique double polarization hysteresis loop with a large maximum polarization (P_max) and a small remnant polarization (P_r), AgNbO₃-based antiferroelectrics (AFEs) have attracted extensive research interest for electric energy storage applications. However, a low dielectric breakdown field (E_b) limits an energy density and its further development. In this work, a highly efficient method was proposed to fabricate high-energy-density Ag(Nb,Ta)O₃ capacitor films on Si substrates, using a two-step process combining radio frequency (RF)-magnetron sputtering at 450 ℃ and post-deposition rapid thermal annealing (RTA). The RTA process at 700 ℃ led to sufficient crystallization of nanograins in the film, hindering their lateral growth by employing short annealing time of 5 min. The obtained Ag(Nb,Ta)O₃ films showed an average grain size (D) of ~14 nm (obtained by Debye–Scherrer formula) and a slender room temperature (RT) polarization–electric field (P–E) loop (P_r ≈ 3.8 μC·cm⁻² and P_max ≈ 38 μC·cm⁻² under an electric field of ~3.3 MV·cm⁻¹), the P–E loop corresponding to a high recoverable energy density (W_rec) of ~46.4 J·cm⁻³ and an energy efficiency (η) of ~80.3%. Additionally, by analyzing temperature-dependent dielectric property of the film, a significant downshift of the diffused phase transition temperature (T_M2–M3) was revealed, which indicated the existence of a stable relaxor-like AFE phase near the RT. The downshift of the T_M2–M3 could be attributed to a nanograin size and residual tensile strain of the film, and it led to excellent temperature stability (20–240 ℃) of the energy storage performance of the film. Our results indicate that the Ag(Nb,Ta)O₃ film is a promising candidate for electrical energy storage applications.