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With the rapid growth of energy storage capacitors in advanced power systems, the pursuit of lightweight devices is gradually gaining importance despite the urgent need for device miniaturization. To reduce the mass of dielectric energy storage materials, certain light metal elements, such as potassium (K) and sodium (Na), offer promising prospects for achieving low material density. However, the intrinsic formation of point defects, including alkali metal vacancies and oxygen vacancies (Schottky defects), is inevitable during high-temperature sintering because of the volatilization of alkali metal oxides. These defects can lead to high conductivity under high electric fields, thereby deteriorating energy storage performance (ESP). In this work, we focus on a potassium-rich composition, K2La0.75Gd0.25Nb5O15, which is characterized by a tetragonal tungsten bronze (TTB) structure, to investigate the impact of volatile point defects. Different types of defects were designed by changing the K2O content, and energy storage properties were investigated. Based on leakage current measurements, impedance spectra, and DFT calculation results, it could be concluded that K–O defects with a shallow energy level cause conduction loss, thereby influencing polarization and ESP. Consequently, a high recoverable energy storage density (Wrec) of 5.02 J cm−3 and an energy efficiency of 85.6% were simultaneously achieved for the composition with the lowest defect content. This work reveals a mechanism in which volatile defects dominate conduction behavior and relevant ESP, stresses the significance of suppressing alkaline Schottky defects, and provides a feasible solution to developing lightweight dielectric energy storage materials. [ABSTRACT FROM AUTHOR]

The development of high-performance electrocaloric (EC) materials is of great interest for solid-state refrigeration employed in microelectromechanical systems. However, superior adiabatic temperature and excellent temperature stability are long-term challenges in the development of electrocaloric refrigeration materials. Herein, we propose a strategy for optimizing EC performance in which an overlap zone based on tetragonal, rhombohedral or pseudo-cubic states is designed by adjusting La content around the morphotropic phase boundary. Their structures witness the phase evolution from ferroelectric to relaxor state and domain evolution from the micron and submicron ferroelectric domain to polar nano-regions, which encompasses many advantages of larger polarization and lower phase transition temperature as well as wider temperature window. Based on this design strategy, a (Pb1−1.5xLax)(Zr0.55Ti0.45)O3 system is employed to establish an overlap zone between rhombohedral and pseudo-cubic structures by adjusting the La content, where a large pyroelectric coefficient ∂P/∂T from the coexistence of rhombohedral and pseudo-cubic phases, a sluggish phase transition from the relaxor state, as well as excellent temperature stability are employed to optimize the EC response. Among them, PLZT (x = 0.12) achieved an optimized ΔTmax of 1.58 K around room temperature. In addition, the enhanced relaxor state favors broadening of the temperature span (Tspan), where a desirable Tspan is up to 100 °C (within 90% variation in maximal temperature). Our research not only provides an avenue for developing high-performance EC materials with better EC performance and wider Tspan but also broadens the application prospects for PLZT ferroelectric ceramics in the field of refrigeration, as well as offering a beneficial design strategy for electrocaloric materials in other systems. [ABSTRACT FROM AUTHOR]

Achieving high energy storage density (ESD), energy storage efficiency (η) and exceptional stability is deemed the foremost challenge for the application of lead-free dielectric energy storage materials. Relaxor ferroelectric (REF) ceramics are one of the most promising candidate materials for energy storage materials by virtue of their low remnant polarization, hysteresis, and high permittivity. Here, we demonstrated that excellent energy storage properties (high recoverable energy storage density Wrec of 5.23 J cm−3 and 5.47 J cm−3 with high η of 89.7% and 90.6%) are achieved in Hf-modified (0.7Ba0.55Sr0.45–0.3Bi0.5Na0.5)TiO3 (BSBNT) relaxor ferroelectric ceramics. Analysis of a first order reversal curve (FORC) and piezoresponse force microscopy (PFM) indicate that the incorporation of Hf can effectively inhibit the polarization nonlinearity and reduce the size of polar nanoregions, resulting in improved energy density and efficiency. Additionally, the introduction of Hf greatly enhances the breakdown strength by improving the electric insulation, suppressing the electronic transition and boosting the bandgap. For practice application, the (0.7Ba0.55Sr0.45–0.3Bi0.5Na0.5)(Ti0.85Hf0.15)O3 ceramics also show excellent temperature (−95 to 125 °C) and frequency (1–1000 Hz) stability at 250 kV cm−1. Meanwhile, the energy storage properties (ESPs) of ceramics can maintain stability even after 106 hysteresis cycles. This work provides a feasible approach that can be employed to develop high-performance lead-free capacitors in high-power electronics and pulse power systems. [ABSTRACT FROM AUTHOR]

An intermediate-sized atomically precise metalloid silver nanocluster [Ag71(SR)31(Dppm)](SbF6)2 (Dppm = bis (diphenylphosphino)methane, SR = S-tBu) is reported, which comprises one building block Ag64, six SR5 pentagons, one sole SR ligand, a DppmAg2 handle, and an Ag5 lid. Structurally, a decahedron Ag23 kernel is observed in the metalloid silver nanocluster. Moreover, the Ag64 unit provides insights into the growth of large clusters such as Ag136(SR)64Cl3 and Ag141(SR)40Br12via assembly. The observed decahedron Ag23 provides a deeper understanding on Marks decahedron in larger nanoclusters, and the [Ag71(S-tBu)31(Dppm)](SbF6)2 uses Ag64 as a building block to predict the structure of larger metalloid nanoclusters. [ABSTRACT FROM AUTHOR]

An intermediate-sized atomically precise metalloid silver nanocluster [Ag71(SR)31(Dppm)](SbF6)2 (Dppm = bis (diphenylphosphino)methane, SR = S-tBu) is reported, which comprises one building block Ag64, six SR5 pentagons, one sole SR ligand, a DppmAg2 handle, and an Ag5 lid. Structurally, a decahedron Ag23 kernel is observed in the metalloid silver nanocluster. Moreover, the Ag64 unit provides insights into the growth of large clusters such as Ag136(SR)64Cl3 and Ag141(SR)40Br12via assembly. The observed decahedron Ag23 provides a deeper understanding on Marks decahedron in larger nanoclusters, and the [Ag71(S-tBu)31(Dppm)](SbF6)2 uses Ag64 as a building block to predict the structure of larger metalloid nanoclusters. [ABSTRACT FROM AUTHOR]

Herein, we report the synthesis and total structure of a Cu-rich alloy nanocluster protected by twelve adamantanethiolate ligands, i.e., [Ag13Cu10(SAdm)12]X3 (–SAdm = SC10H15, X = counterion), which was confirmed by single-crystal X-ray structure determination and electrospray ionization mass spectrometry (ESI-MS). X-ray crystallographic analysis indicated that [Ag13Cu10(SAdm)12]X3 consisted of an icosahedral Ag13 core, covered by a cage-like shell of Cu10(SAdm)12. Furthermore, density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations on the geometric and electronic structures and KS orbitals and UV-vis spectroscopy were performed on the model [Ag13Cu10(SMe)12]3+ and its monometallic analog [Ag23(SMe)12]3+. This work will deepen the understanding of core–shell Ag–Cu alloy nanoclusters. [ABSTRACT FROM AUTHOR]

The phase boundaries of dielectric materials have constantly been valuable for instructing the design of phase structures, revealing correlations between compositions and structures, and attaining the desired functional properties for piezoelectric, pyroelectric, electrostriction, electrocaloric, energy storage and energy harvesting applications. We here observe a new type of phase boundary in a solid solution of xPbTiO3·(1 − x)Pb(Yb1/2Nb1/2)O3 (x = 0.00–0.20), which is between an antiferroelectric (AFE) phase and a relaxor ferroelectric (RFE) phase. x = 0.10 is confirmed as the phase boundary. XRD, TEM, PFM and Raman spectroscopy analysis reveal two fundamental traits of the phase structure: (1) the polar state changes from AFE to FE order; and (2) the domain range evolves from micrometer-sized to nanometer-sized, both of which are normally separated but coexist around the phase boundary. The intriguing phase structure contributes to the distinctive dielectric properties: (1) a broad compositional zone (x < 0.10 and x ≥ 0.14) features low remnant polarization, low hysteresis and highly reversible domain wall motion, and is expected to be utilized for dielectric energy storage and electrostriction applications; and (2) a narrow nonergodic RFE zone (0.10 ≤ x < 0.14) demonstrates remnant and maximum polarization, co-dominated by composition and temperature, and has potential for pyroelectric and electrocaloric applications. [ABSTRACT FROM AUTHOR]

An intermediate-sized atomically precise metalloid silver nanocluster [Ag 71 (SR) 31 (Dppm)](SbF 6 ) 2 (Dppm = bis (diphenylphosphino)methane, SR = S- t Bu) is reported, which comprises one building block Ag 64 , six SR 5 pentagons, one sole SR ligand, a DppmAg 2 handle, and an Ag 5 lid. Structurally, a decahedron Ag 23 kernel is observed in the metalloid silver nanocluster. Moreover, the Ag 64 unit provides insights into the growth of large clusters such as Ag 136 (SR) 64 Cl 3 and Ag 141 (SR) 40 Br 12 via assembly. The observed decahedron Ag 23 provides a deeper understanding on Marks decahedron in larger nanoclusters, and the [Ag 71 (S- t Bu) 31 (Dppm)](SbF 6 ) 2 uses Ag 64 as a building block to predict the structure of larger metalloid nanoclusters.

Herein, we report the synthesis and total structure of a Cu-rich alloy nanocluster protected by twelve adamantanethiolate ligands, i.e., [Ag 13 Cu 10 (SAdm) 12 ]X 3 (-SAdm = SC 10 H 15 , X = counterion), which was confirmed by single-crystal X-ray structure determination and electrospray ionization mass spectrometry (ESI-MS). X-ray crystallographic analysis indicated that [Ag 13 Cu 10 (SAdm) 12 ]X 3 consisted of an icosahedral Ag 13 core, covered by a cage-like shell of Cu 10 (SAdm) 12 . Furthermore, density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations on the geometric and electronic structures and KS orbitals and UV-vis spectroscopy were performed on the model [Ag 13 Cu 10 (SMe) 12 ] 3+ and its monometallic analog [Ag 23 (SMe) 12 ] 3+ . This work will deepen the understanding of core-shell Ag-Cu alloy nanoclusters.