High Polarization Research Articles

Pressure effect investigation of structural, electronic, elastic and magnetic properties of X2CrSb (X = Mn, Co and Cu) Heusler alloys

Using the plane-wave pseudo-potential approach and generalized-gradient approximation for the exchange–correlation effects in the framework of the density functional theory, the structural, electronic, elastic and magnetic properties of X2CrSb ( ▪ and Cu) Heusler alloys were investigated. For ▪ , a structural phase-transition from XA to L21-phase is expected at 8.933GPa. This compound exhibits half-metallic behavior before becoming a magnetic metal at 17.5GPa. The ▪ is a half-metal under expansion and nearly half-metal above 1GPa. The total magnetic moments for ▪ , ▪ and ▪ are respectively equal to 5.0μB, 1.0μB and 3.4μB, and are mainly localized on Cr except for ▪ in XA-phase where the magnetic moment is localized on Mn. The DOS analysis shows weak spin-polarizations for ▪ and a higher polarization under expansion for ▪ and ▪ . Under compression, the polarization is weakened in ▪ , it remains at a high level before it vanishes at 29.4μB in ▪ .

Significantly improved energy storage performance of Na0.5Bi0.5TiO3–BaTiO3 ferroelectric ceramics with a wide temperature range via high-entropy doping

The emergence of high-entropy perovskite materials provides a new research idea to solve the problem of high remnant polarization and low recoverable energy storage density (Wrec) of relaxor ferroelectrics. In this study, barium-based high-entropy perovskite oxides Ba(Zr0.2Sn0.2Hf0.2Nb0.2Ti0.2)O3 (BZSHNT) were introduced into the 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 (BNT-6BT) ceramic by the conventional solid state sintering method. The 0.2BZSHNT doped BNT-6BT ceramic demonstrates significantly improved Wrec of 3.57 J/cm3 and a high efficiency of 81.6 % compared to those of the BNT-6BT ceramic, which is only 0.5 J/cm3 and 60 % respectively. The doped BZSHNT refines the hysteresis loops and drastically reduces the remnant polarization, which lead to the increase of the polarization difference. The 0.8(BNT-6BT)-0.2BZSHNT ceramics show high discharge energy density, good temperature stability (25–200 °C), excellent frequency stability (10–300 Hz) and superior discharge rate (t0.9 = 83 ns) because of its increased TiO6 lattice distortion, atomic disorder, relaxation degree and band gap, as well as the disruption of the long-range ordered ferroelectric domains. Our findings make BNT-6BT doped BZSHNT based ceramics one of the most promising lead-free dielectric energy storage candidates.

98 fs High Energy Stable Hybrid Mode-Locked Nonlinear Polarization Rotation With CuO-Doped ZnO Saturable Absorber

98 fs High Energy Stable Hybrid Mode-Locked Nonlinear Polarization Rotation With CuO-Doped ZnO Saturable Absorber

Output performance of zinc tin oxide nanoparticle-based piezoelectric nanogenerators with different shapes and phases

This study reports the characteristics of a piezoelectric nanogenerator (PENG) consisting of a mixture of polydimethylsiloxane (PDMS) and zinc tin oxide (ZTO) particles (ZTO@PDMS) with different shapes and phases. The output performance of PENGs with crystalline Zinc hydroxystannate(ZHS), amorphous ZTO, and crystalline ZTO of different phases was investigated based on annealing temperature. The fabricated PENGs with amorphous ZTO (a-ZTO) cubes showed a maximum output voltage of ∼4.3V and a current of ∼470 nA with a power of 3.14 μW, which is 249 % higher than that of the crystalline ZTO (c-ZTO) cube-based one. The amorphous ZTO (a-ZTO) nanosphere showed the highest output performance. The surface area of the piezoelectric material affected the residual polarization, which led to different piezoelectric properties. Therefore, we investigated the output performance of PENGs with various shapes while maintaining the same volumes of ZTO cubes and spheres. The molar ratio of the materials was varied during synthesis, revealing that the ZTO cubes have a higher output performance. The polarization-electric loops (P-E loops) showed a high remnant polarization (Pr∼25.89μC/cm2) in ZTO@PDMS films with larger 1103 nm cubes. These values were 170.5 %, 143.7 %, and 113.2 % larger than those observed in ZTO@PDMS films with cubes of size 826 nm, 978 nm, and 1047 nm, respectively. The ZTO nanocubes have a significant advantage in the fabrication of high output performance based on PENGs.

High energy storage performance in BTO-based ferroelectric films

Dielectric capacitors play an increasingly important role in modern electronic power systems due to their ultrahigh charging and discharging speeds and power density. Much research has focused on enhancing dielectric breakdown strength to achieve better energy storage performance; however, this increases the potential for heat generation and unexpected insulation failures, thereby affecting the stability and lifespan of devices. This study introduces a small amount of Na+ dopants at the A-site of BaTiO3, inducing lattice distortions and enhancing local polarization to increase energy storage density rather than through enhancing breakdown strength. The introduction of Na+ enhances the ferroelectric properties, with polar nano-regions (PNRs) gradually evolving into long-range ordered large domains. In the Ba0.985Na0.015TiO3 films, the coexistence and coupling of abundant PNRs with a few long-range ordered ferroelectric domains result in high saturation polarization and low residual polarization. At a moderate electric field of 2.3 MV cm−1, an ultrahigh energy density of 44.3 J cm−3 and a high energy storage efficiency of 78.6 % were obtained. Additionally, the film exhibits excellent frequency stability (100 Hz-20 kHz), temperature stability (30–180 °C), fatigue resistance (107 cycles), and high pulsed discharge energy density, along with great thermal stability. This work provides new insights into achieving exceptional energy storage performance in single-phase films.

Polymorphic Localized Heterostructure Design for High-Performance Amorphous/Nanocrystalline Composite Film.

Analogous to linear dielectric, amorphous perovskite dielectrics characterized of high breakdown strength and low remanent polarization possess in-depth application in the sea, land, and air fields. Amorphous engineering is a common approach to balance the inverse relationship between polarization and breakdown strength in dielectric ceramic capacitor, however, the low polarization is the major barrier limiting the improvement of energy storage density. To address this concern, the polymorphic localized heterostructure confirmed by high-resolution transmission electron microscope (HR-TEM) and HADDF images is constructed in BaTiO3-Bi(Ni0.5Zr0.5)O3 amorphous/nanocrystalline composite film with SiO2 addition (BT-BNZ-xS, x = 3, 5, 7, 10 mol%). The stability of nanocrystalline region achieved by Si-rich transition region and the enhancive ultra-short-range ordering in the amorphous region synergistically result in large breakdown strength and nonhysteretic polarized response. This polymorphic localized heterostructure optimizes the thermal stability in a wide temperature range and contributes ultrahigh energy storage density of 149.9 J cm-3 with markedly enhanced efficiency of 79.0%. This study provides a universal strategy to design the polarization behavior in other amorphous perovskite-based dielectrics.

In-situ ionothermal synthesis of nanoporous carbon/oxide composites: A new key to functional separators for stable lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) with high energy density are promising for energy storage. However, conventional polypropylene-based separator cannot avoid polysulfides shuttling which impedes the practical application of LSBs. Herein, an in-situ ionothermal synthesis strategy that concurrently applies ionic liquid as the solvent, template and high-yield carbon source is proposed for the facile preparation of nanoporous carbon/oxide composite separator modifiers. The composites exhibit features of high polarity, self doping, oxygen vacancy, heteroatom doping, abundant defects and high electronic conductivity. Theoretical and experimental studies suggest that the composites can efficiently trap and convert polysulfides for high-performance LSBs. Indeed, in the composite-modified LSBs with next-generation roll-to-roll dry-processed high-loading sulfur cathodes, enhanced performance is achieved, revealing the effectiveness of the composites as functional materials towards separator modification. Therefore, the proposed strategy and its delivered nanoporous composites exhibit excellent versatility and practicality for high-performance LSBs.

Functional Medium Entropy Alloys for Joint Replacement: An Atomistic Perspective of Material Deformation and a Correlation to Wear, Corrosion, and Biocompatibility

The present study adopts a muti-facet approach to design bio inspired concentrated alloys for potential application as articulating surfaces in joint replacements. A series of equiatomic, Nb rich and Ti rich TiMoNbZr based medium entropy alloys (MEAs) were processed via arc melting and their mechanical, in-vitro corrosion, wear, and in vitro and in vivo biocompatibility were investigated. Equiatomic MEA had primarily bcc with minor hcp phases where the single bcc was achieved with the addition of Nb. The single bcc Nb rich alloy resulted in 13% elongation, much higher than equiatomic or Ti rich alloy. All the MEAs showed comparatively higher yield strength due to the climb of edge dislocations which is the main rate limiting mechanism at 300 K, as evident molecular dynamics (MD) simulation. The locally fluctuating energy landscape promotes kinks on edge dislocation, and at local minima nanoscale segments gets pinned. Upon yielding the entangled kink leaves a trail of vacancies/interstitials and escapes via climb motion to render high yield strength. The higher corrosion and pitting resistance of Nb enriched alloys can be attributed to the stable ZrO2, Nb2O5, TiO2, and MoO3 oxides, high polarization resistance (106-105 Ωcm−2), and low defect densities (1016-1018). In vitro cell-materials interaction using MC3T3-E1 showed bioinert but cytocompatible nature of the MEAs. The wear rate of the MEAs was in the range of 7-9×10−5 mm3N−1m−1. The wear debris did not show any tissue necrosis when implanted in rabbit femur rather new bone regeneration can be seen around the particles. Statement of SignificanceIn the present work, a noble Nb enriched MEAs with superior mechanical, in vitro wear, corrosion and cytocompatibility properties was designed for articulating surfaces in joint replacement.•Single bcc in Nb enriched MEAs resulted in 13 % elongation with high hardness and yield strength.•Climb of entangled edge segment is the rate limiting mechanism in controlling high yield strength of MEAs at 300 K.•High polarization resistance (106-105 Ωcm−2), and low defect densities (1016-1018) attributes to ZrO2, Nb2O5, TiO2, and MoO3 oxides enriched passive film.•Wet sliding wear rate ranged in order 7-9×10−5 mm3N−1m−1. In-situ generated wear debris when implanted in rabbit femur did not show any tissue necrosis rather new bone regeneration was observed around debris.

Research on polarization compensation for practical satellite-based quantum key distribution

Satellite-based quantum key distribution (QKD) is one of the effective solutions for building a global-scale quantum network. For practical satellite-based polarization-encoding QKD systems, the polarization degradation introduced by the single-mode fiber and the relative rotation between satellites and ground stations will lead to a decrease in the polarization performance and need to be compensated. In this work, we propose two novel on-orbit satellite-to-ground joint polarization measurement and compensation methods, which can ensure high polarization fidelity while effectively saving hardware resources and reducing costs. By establishing a polarization compensation model and performing theoretical analysis, combined with desktop experimental verification, we demonstrated the effectiveness of the satellite-to-ground joint polarization compensation and achieved a low quantum bit error rate below 0.3% after background removal. The presented polarization compensation laid the foundation for the subsequent applications in satellite-based QKD and satellite-based quantum networks.

Sustainable 3D-printed cellulose-based biocomposites and bio-nano-composites: Analysis of dielectric performances

The development of cellulose-reinforced biomaterials appears to be an attractive approach for the production of sustainable materials with good mechanical properties. Although 3D printing of cellulose-reinforced biomaterials has become popular, there is very little feedback regarding their use in electrical insulation applications. This study aims to propose bio-nano-composites containing polylactic acid (PLA), microcrystalline (MCC) and nanocrystalline (NCC) cellulose by fused filament fabrication (FFF) for electrical insulation applications. The influence of the 3D printing process, cellulose content and filler size on dielectric properties was investigated. The addition of cellulosic fillers, and considering their high polarity, increased the dielectric constant (ε'), dielectric loss (ε''), as well as the AC electrical conductivity (σAC) of the composites. Cellulosic fillers also increased the crystallization rate of the materials. At equivalent content, the highest polarization potential were observed for NCC-based composites and were attributed to the nanofiller's better dispersion and available specific surface area. Finally, the 3D printing process affects all the measured properties, due to a combined effect (lower crystalline content and voids presence). The porosity rate was measured at 2.5 % for the neat PLA and increased progressively from 3.1 % to 5.8 % for the cellulose-based composites. These findings showed the benefits provided by the FFF technology in the production of cellulose-based biocomposites with good electrical insulation properties, while noting some needed feedback on the thermomechanical properties of such materials.

Design of High‐Entropy Relaxor Ferroelectrics for Comprehensive Energy Storage Enhancement

AbstractFor an ideal electrostatic energy storage dielectric capacitor, the pursuit of simultaneously high energy density and efficiency presents a formidable challenge. Typically, under an applied electric field, an increase in energy density is usually accompanied with a deteriorated energy storage efficiency due to the escalated hysteretic loss, which is harmful to the reliability of the capacitor. Thus, a well‐balanced performance of improved energy density and maintained high efficiency is highly demanded. In this work, a structure with amorphous phases embedded in polycrystalline nanograins using the entropy tactic, leading to a higher transport barrier of carrier is constructed. Hence, the hysteretic loss is largely suppressed at a high electric field and the high polarization is still sustained in the high‐entropy film. Consequently, an ultrahigh energy density of 139.5 J cm−3 with a high efficiency of 87.9%, and a high figure of merit of 1153 are simultaneously achieved in the high‐entropy Ba2Bi4Ti5O18‐based relaxor ferroelectric. This work offers a promising avenue in materials structure design for advanced high‐power energy storage applications.

Construction of molecular semiconductor traps to improve the energy storage performance of novel cyanopolynorbornene

To meet the demand of film capacitors in harsh condition applications, research workers devote their effort to develop high temperature resistant polymer dielectrics with high energy density. In this paper, a new type of dipole glass polymer, polynorbornene containing cyano-group side chain (PDMBN) is prepared by ring opening metathesis polymerization. The high dipole moment of the cyano-group possesses high polarization, resulting in that the discharge energy density (Ud) of 8.6 J/cm3 and efficiency of 84 % are found in the PDMBN at room temperature. Via using three organic semiconductors with increased electron affinity (NBTI, NBTI-SO2 and NBTI-2SO2) as the fillers, the energy storage properties of PDMBN matrix are further improved due to the binding effect of free electrons. In addition, the interfacial barrier height is inversely proportional to the temperature, electric field and electron affinity of fillers. As a result, 0.7- wt% NBTI-SO2/PDMBN achieves a maximal Ud of 11.6 J/cm3 at 600 MV/m and room temperature. At elevated temperatures, the conduction loss of polymer PDMBN increases sharply, causing a rapid decline in energy storage performance. Nevertheless, the maximum Ud of 0.7-wt%NBTI/PDMBN composite film at 100 °C and 150 °C can reach 6.2 J/cm3 and 4.5 J/cm3, respectively. This study is helpful for the design of polynorbornene dielectrics, and provides an important reference for the construction of carrier traps in polymer dielectrics at high temperature.

Boosting energy storage via the strong interaction between Cu2O clusters and carbon rich framework

Metal oxides have attracted tremendous attention because of their easy fabrication, high reversible voltage, and decent electrochemical capacity in lithium ion batteries. However, the conversion of their structure and the low electric conductivity always lead to a high polarization and poor cyclic stability. Herein, the strong interaction between Cu2O and porous carbon-rich framework is constructed through an in-situ synthesis method. Benefit from the synergistic effect derived from this interaction, the confined size and the high reversibility in chemical reaction of Cu2O are realized. In the hybrid system, the conjugated carbon skeleton with acetylene bond plays crucial role not only in building strong interactions, but also in interconnecting numerous Cu2O clusters for the transport of charge and storing of ions in a homogeneous solid. Hence, the composite material of porous carbon-rich material and Cu2O electrode delivers a decent capacity of 804 and 305 mAh g–1 in lithium and sodium ion batteries, respectively. These results suggest the great potential of such carbon framework/metal oxides composite material applied for high performance battery.

Excellent energy storage performance in BSFCZ/AGO/BNTN double-heterojunction capacitors via the synergistic effect of interface and dead-layer engineering

Dielectric films with ultra-high energy storage density and efficiency are urgently needed due to the energy crisis. Here, we construct novel ferroelectric/dead-layer/superparaelectric (FE/DL/SPE) double-heterojunction capacitors, utilizing interface and dead-layer engineering to achieve outstanding energy storage performance. Bi0.9Sm0.1Fe0.9Co0.05Zn0.05O3 (BSFCZ) with large polarization, Ba0.985Na0.015Ti0.95Ni0.05O3 (BNTN) with low hysteresis and high breakdown strength (Eb), and artificial Al0.9Ga0.1O3 (AGO) with wide band-gap were chosen as the FE, SPE, and DL phases, respectively. Interface engineering enables the BSFCZ/AGO/BNTN films to maintain a high polarization of 55 μC cm−2, while the linear dielectric AGO and SPE BNTN substantially suppresses the remnant polarization. This can be clarified by the evolution of domains in the BSFCZ layer: nanodomains are scaled down to polar clusters, reducing polarization hysteresis while maintaining relatively high polarization. Simultaneously, two opposing intrinsic electric fields are formed to offset a portion of the external electric field, and the low dielectric constant AGO layer bears a significant part of the applied electric field due to electromagnetic boundary conditions. Consequently, the Eb is significantly increased from 4.4 MV cm−1 of BSFCZ/BNTN to 5.5 MV cm−1 of BSFCZ/AGO/BNTN, resulting in a giant recoverable energy density of 132 J cm−3 and a high efficiency of 84 % in BSFCZ/AGO/BNTN films. Moreover, the BSFCZ/AGO/BNTN films excel in temperature stability (RT∼200 °C), fatigue resistance (up to 107 cycles), and frequency stability (200 Hz to 20 kHz), alongside an exceptionally rapid discharge rate of 2.6 μs. This innovative approach suggests new possibilities for producing environmentally friendly, large-area, high-performance dielectric capacitors.

Robust parahydrogen-induced polarization at high concentrations.

Parahydrogen-induced polarization (PHIP) is a potent technique for generating target molecules with high nuclear spin polarization. The PHIP process involves a chemical reaction between parahydrogen and a target molecule, followed by the transformation of nuclear singlet spin order into magnetization of a designated target nucleus through magnetic field manipulations. Although the singlet-to-magnetization polarization transfer process works effectively at moderate concentrations, it is observed to become much less efficient at high molar polarization, defined as the product of polarization and concentration. This strong dependence on the molar polarization is attributed to interference due to the field produced by the sample magnetization during polarization transfer, which leads to complex dynamics and can severely affect the scalability of the technique. We address this challenge with a pulse sequence that suppresses the influence of the distant dipolar field, while simultaneously achieving singlet-to-magnetization polarization transfer to the desired target spins, free from restrictions on the molar polarization.

High-efficiency polarization-selective two-dimensional diffraction gratings based on silver cuboid arrays

A two-dimensional (2D) diffraction grating based on silver cuboid arrays is demonstrated. With the structural optimization by three-dimensional (3D) finite-difference time-domain method, the proposed grating exhibits favorable polarization selectivity. At wavelength 1550 nm, high diffraction efficiency and polarization correlation can be realized in the case of two-port output ((0, ±1) or (±1, 0)) under TE polarization, as well as five-port output ((0, 0), (0, ±1) and (±1, 0)) under TM polarization. Under the two-port output state, the diffraction efficiency is nearly 48% with the extinction ratio of 16.44 dB and insertion loss of 0.20 dB. Under the five-port output status, the efficiency is larger than 19% for each diffraction order, meanwhile, the total efficiency and uniformity are 97% and 0.58%, respectively. The proposed grating with positive implications has good potentials in polarization multiplexing and polarization-correlated grating interferometry.

Variable Radio Emission of Neutron Star X-Ray Binary Ser X–1 during Its Persistent Soft State

Ser X–1 is a low-mass neutron star X-ray binary and has been persistently accreting since its discovery in the 1960s. It has always been observed to be in a soft spectral state and has never showed substantial long-term X-ray variability. Ser X–1 has one previous radio observation in the literature in which radio emission was detected during this soft state, which is contrary to the behavior of black hole X-ray binaries. We have recently obtained 10 randomly sampled radio epochs of Ser X–1 in order to further investigate its anomalous soft-state radio emission. Out of 10 epochs, we find 8 nondetections and 2 detections at 10 GHz flux densities of 19.9 ± 4.2 μJy and 32.2 ± 3.6 μJy, respectively. We do not detect polarization in either epoch, ruling out very high polarization levels (≲63% and 34%). We compare these Ser X–1 results to other X-ray binaries and consider explanations for its long-term variable radio behavior.

Hyperpolarizing Small Molecules using Parahydrogen and Solid-State Spin Diffusion.

Parahydrogen-induced polarization (PHIP) is an inexpensive way to produce hyperpolarized molecules with polarization levels of >10 % in the solution-state, but is strongly limited in generality since it requires chemical reactions/ interactions with H2. Here we report a new method to widen the scope of PHIP hyperpolarization: a source molecule is produced via PHIP with high 13C polarization, and precipitated out of solution together with a target species. Spin diffusion within the solid carries the polarization onto 13C spins of the target, which can then be dissolved for solution-state applications. We name this method PHIP-SSD (PHIP with solid-state spin diffusion) and demonstrate it using PHIP-polarized [1-13C]-fumarate as the source molecule, to polarize different 13C-labelled target molecules. 13C polarizations of between 0.01 and 3 % were measured on [1-13C]-benzoic acid, depending on the molar ratio of fumarate:benzoate in the solid state. We also show that PHIP-SSD does not require specific co-crystallization conditions by grinding dry powders of target molecules together with solid fumarate crystals, and obtain 13C signal enhancements of between 100 and 200 on [13C,15N2]-urea, [1-13C]-pyruvate, and [1-13C]-benzoic acid. This approach appears to be a promising new strategy for facile hyperpolarization based on PHIP.

Hyperpolarizing Small Molecules using Parahydrogen and Solid‐State Spin Diffusion

AbstractParahydrogen‐induced polarization (PHIP) is an inexpensive way to produce hyperpolarized molecules with polarization levels of >10 % in the solution‐state, but is strongly limited in generality since it requires chemical reactions/ interactions with H2. Here we report a new method to widen the scope of PHIP hyperpolarization: a source molecule is produced via PHIP with high 13C polarization, and precipitated out of solution together with a target species. Spin diffusion within the solid carries the polarization onto 13C spins of the target, which can then be dissolved for solution‐state applications. We name this method PHIP‐SSD (PHIP with solid‐state spin diffusion) and demonstrate it using PHIP‐polarized [1‐13C]‐fumarate as the source molecule, to polarize different 13C‐labelled target molecules. 13C polarizations of between 0.01 and 3 % were measured on [1‐13C]‐benzoic acid, depending on the molar ratio of fumarate:benzoate in the solid state. We also show that PHIP‐SSD does not require specific co‐crystallization conditions by grinding dry powders of target molecules together with solid fumarate crystals, and obtain 13C signal enhancements of between 100 and 200 on [13C,15N2]‐urea, [1‐13C]‐pyruvate, and [1‐13C]‐benzoic acid. This approach appears to be a promising new strategy for facile hyperpolarization based on PHIP.

Utilizing Domain Engineering to Achieve High-Polarization Relaxor Ferroelectrics for Low-Consumption Ceramic Capacitors.

This study focuses on incorporating NaNbO3 (NN) into the Ba0.85Ca0.15Zr0.9Ti0.1O3 (BCZT) lattice to form (1 - x)BCZT-xNN ceramics. Although antiferroelectricity was not observed, an observed domain-movement-diminishment behavior with increasing NN dopant induced the formation of high polarization walls (HPWs) between adjacent C-phases. The 0.90BCZT-0.10NN composition exhibited superior polarization compared to most BCZT-based ferroelectrics, as validated by mathematical derivation. Integration of these findings revealed a Wrec of 3.86 J/cm3 at 360 kV/cm, with a high Wrec/Eb ratio defining energy consumption efficiency in dielectric capacitors. This work introduces a novel approach to fabricating low-consumption dielectric capacitors. Additionally, a significantly high Wrec of 5.36 J/cm3 was achieved with an NN dopant concentration of 0.30.