Competitive Candidate Research Articles

Enhanced Efficiency and Stability of Triple-Cation Perovskite Solar Cells through Engineering of the Cell Interface with Phenylethylammonium Thiocyanate.

It is reported that the tricationic mixed halide perovskite Csx(FAyMA1-y)1-xPb(IzBr1-z)3 (CsFAMA) possesses a stable crystal structure and outstanding bandgap tunability, rendering it one of the most competitive candidates for commercial perovskite solar cells (PSCs). Nevertheless, the numerous defects at the interface of the tricationic perovskite give rise to a significant constraint on the light capture performance of the device. Simultaneously, water molecules form intermediate compounds with the perovskite at the interface via hydrogen bonds, accelerating the degradation of the perovskite. This study reports the introduction of two-dimensional (2D) phenylethylthiocyanate (PEASCN) at the interface of three-dimensional (3D) perovskite. This approach significantly passivates the surface defects of the perovskite. Concurrently, due to the propensity of the organic ammonium cation PEA+ to interact with the FA+ base within the perovskite, SCN- is exposed outward to form a small-molecule hydrophobic layer. This method markedly reduces the loss of charge recombination and significantly enhances the device stability. The results indicate that the efficiency of the conventional device treated solely with PEASCN is as high as 23.94%. The unsealed device retains 85.12% of its initial efficiency after being placed in a conventional environment for 500 h. Furthermore, this surface passivation and hydrophobic strategy can be universally applicable to perovskite types with a high FA+ content.

Optimizing hydrogen storage in a heterogeneous aquifer considering hysteresis and dissolution

Hydrogen (H2) is a rising solution for carbon-neutral fuel transition. Saline aquifer, ubiquitous underground, is a competitive candidate for large-scale underground hydrogen storage (UHS). This study proposed to use a heterogeneous aquifer formation for probing the functioning of UHS and optimizing its operation. By integrating geological information with lithofacies from the Ordos Basin in China, a heterogeneous triplet aquifer model was built, upon which compositional simulations of UHS operations that consider two-phase flow, relative permeability hysteresis, hydrogen and water phase behavior, rock compressibility, and dissolution mechanisms were conducted. Orthogonal array L25 (56) with mixed levels was designed to optimize the H2 recovery. Results substantiate the feasibility of storing millions of cubic meters of H2 with over 95% recovery. Ignoring dissolution and relative permeability hysteresis will result in an overestimation of the hydrogen recovery factor, with the effect of relative permeability hysteresis being more significant. Provided equal cycle length, a lower injection-withdrawal rate is suitable for long-term operation of hydrogen storage, while a higher rate can achieve a higher recovery factor during the early cycles. Measures of lowering the skin factor and pre-extracting brine could improve storage capacity and reduce water production during injection and withdrawal. The optimized case is expected to achieve an average H2 recovery of 98.8% for 30 operation cycles with moderately low saline water production. These findings provide valuable insights for developing large-scale and cost-effective UHS in saline aquifers.

A compact broadband circularly polarized monopulse slot array antenna based on gap waveguide technology

ABSTRACT This paper presents a circularly polarized (CP) monopulse slot array antenna based on gap waveguide (GWG) technology. The proposed monopulse antenna is composed of a 4 × 4 array antenna fed by the monopulse comparator network in a compact three-layer structure. To achieve a broad axial ratio (AR) bandwidth of right-handed circular polarization (RHCP) in the sum radiation pattern, a septum polarizer is used in the radiating aperture. Based on this approach, horizontal transition structures are used to excite the radiating array from the WR-28 waveguide to the GWG, which helps to reduce the reflection loss and expand the impedance bandwidth. Experimental results show that the impedance bandwidth is 30.5 GHz to 40 GHz, which is 27.1%. The 3 dB AR bandwidth is 31%. The measured null depth is −40 dB, and the maximum measured gain in the sum pattern is 22 dBi at 34 GHz, while the antenna efficiency is greater than 86%. The advantages of low loss, broad bandwidth, and compact structure make the proposed antenna a competitive candidate for millimeter-wave (mmWave) monopulse direction-finding applications.

Minimizing Voltage Deficit in Perovskite Indoor Photovoltaics by Interfacial Engineering.

Metal halide perovskites with bandgap of ≈1.8eV are competitive candidates for indoor photovoltaic (IPV) devices, owing to their superior photovoltaic properties and ideal absorption spectra matched to most indoor light sources. However, these perovskite IPVs suffer from severe trap induced non-radiative recombination, resulting in large open-circuit voltage (VOC) losses, particularly under low light intensity. Herein, an effective approach is developed to minimizing trap density by modifying the buried interface of perovskite layer with bifunctional molecular 2-(4-Fluorophenyl)ethylamine Hydrobromide (F-PEABr). The benzene ring of F-PEABr molecules can firmly anchor at the hole transporting layer by π-π stacking interaction, and the other ends can passivate the defects on the buried interface of perovskite layer. Based on that, the F-PEABr modified perovskite IPVs achieved power conversion efficiency (PCE) of 42.3% with a remarkable VOC of 1.13V under 1000 lux illumination from a 4000K LED lamp. Finally, perovskite IPV mini-modules with area of 10.40cm2 are demonstrated with a PCE of 35.2%. This interface modification strategy paves the way for crafting high-performance perovskite IPVs, holding great potential for self-powered internet of things applications.

Ultra-miniaturized HMSIW cavity-backed reconfigurable antenna diplexer employing dielectric fluids with wide frequency tuning range

This communication presents an ultra-miniaturized two-way frequency tunable antenna diplexer based on cavity-backed slots and dielectric fluids. The proposed antenna utilizes two half-mode substrate-integrated rectangular cavities loaded with slots and fluidic pockets. The conventional size reduction is achieved by employing half-mode cavities, whereas ultra-miniaturization is obtained by applying the slots, which provides additional capacitive loading. As the cavities are of unequal sizes, a weak cross-coupling path is created between the ports to obtain high isolation (> 30 dB). The isolation is further enhanced by loading the slots. Two mechanisms are analyzed to tune the frequency bands individually or simultaneously. Firstly, the width of the slots can be altered to tune the frequency bands. However, this method involves modification of the physical dimensions of the antenna. Secondly, fluidic vias are created on the bottom plane of the cavities. These can be filled with various dielectric liquids to achieve frequency reconfigurability without altering the physical dimensions of the antenna. To demonstrate the concepts considered, the prototype of the proposed antenna was fabricated and experimentally validated. The structure has a footprint of 0.045λg2 and an isolation exceeding 33.4 dB. The operating frequencies are tunable in the range from 3.08 to 3.84 GHz (lower band) and from 4.97 to 6.33 GHz (upper band) by varying the dimensions of the slots whereas the operating frequencies are reconfigurable in the range from 2.74 to 3.38 GHz (lower band) and from 4.54 to 5.58 GHz (upper band), by employing microfluidic approach. As a result, the working frequencies may be varied in the range from 2.74 to 3.84 GHz (lower band) and from 4.54 to 6.33 GHz (upper band), making this antenna diplexer a competitive candidate for several communication systems. The cross-polarization levels, front-to-back ratio, and realized gain are greater than 19 dB, 18 dB, and 2. dBi, respectively. Excellent consistency is observed between full-wave simulation results and the measurement data.

Stress-induced artificial neuron spiking in diffusive memristors

Diffusive memristors owing to their ability to produce current spiking when a constant or slowly changing voltage is applied are competitive candidates for development of artificial electronic neurons. These artificial neurons can be integrated into various prospective autonomous and robotic systems as sensors, e.g. ones implementing object grasping and classification. We report here Ag nanoparticle-based diffusive memristor prepared on a flexible polyethylene terephthalate substrate in which the electric spiking behaviour was induced by the electric voltage under an additional stimulus of external mechanical impact. By changing the magnitude and frequency of the mechanical impact, we are able to manipulate the spiking response of our artificial neuron. This functionality to control the spiking characteristics paves a pathway for the development of touch-perception sensors that can convert local pressure into electrical spikes for further processing in neural networks. We have proposed a mathematical model which captures the operation principle of the fabricated memristive sensors and qualitatively describes the measured spiking behaviour. Employing such flexible diffusive memristors that can directly translate tactile information into spikes, similar to force and pressure sensors, could offer substantial benefits for various applications in robotics.

High-performance cold-source field-effect transistors based on Cd3C2/ boron phosphide heterojunction

To overcome the short-channel effect and large gate leakage current in the field-effect transistors (FETs), some cold-source materials have been suggested as alternative materials. We explore the performance of FET based on the cold-source material Cd3C2 using the ab initio quantum transport method. It is shown that the figure of merits (FOMs) of Cd3C2/ Boron phosphide (BP) FET satisfies the requirements of ITRS2028 HP for UL=2 and UL=3nm. The performance of Cd3C2/BP FET is improved when Cd3C2 is p-type doped. Doping causes a super-exponential decrease in carrier concentration, thus the cold-source FET based on Cd3C2/BP is formed. When the doping concentration reaches 10.0 × 1013cm−2, the device satisfies the requirements of ITRS2028 HP. More importantly, at the doping concentration of 10.0 × 1013cm−2 for UL=2 and 3 nm, the subthreshold swings are 52.32 and 56.84 mV/dec, which are lower than 60 mV/dec. This work proposes a new cold-source FET based on Cd3C2/BP, whose excellent performance can make it a competitive candidate in future electronic devices.

Heat Treatment of PTFE/PDMS/Nano‐silica Deposited Layer for Preparation of Superhydrophobic Coating with Anti‐corrosion, Anti‐scaling, and Anti‐fouling Properties

AbstractPTFE‐based superhydrophobic coatings have received increasing research and the fabricated coatings exhibited excellent anti‐corrosion, anti‐scaling, anti‐fouling, and anti‐icing properties. In order to further enhance the hydrophobicity of PTFE coating, a PTFE‐based coating consisted of nano‐silica and polydimethylsiloxane (PDMS) was fabricated by deposition coating and annealing treatment. The water contact angle and sliding angle of the coating achieved 160.65° and 3.02°, respectively, demonstrating it possessed superhydrophobic property. Due to its excellent surface feature, the coating exhibited resistance to milk, coffee, and mud water, and could be easily cleaned by water flow. Besides, the water droplet on the coating had a longer freezing time and the ice droplet could be easily removed from the coating. Ascribed to the abundant nonpolar groups and the air cushion formed under water, the prepared coating had outstanding anti‐scaling and anti‐corrosion properties. The electrochemical impedance of the steel plate with the coating (above 9000 Ω·cm2) increased by two orders of magnitude compared with the non‐coating one (78.2 Ω·cm2), and the anti‐scaling rates of the coating towards BaSO4 and SrSO4 were all above 80%. It is promising that the coating will be a competitive candidate in many application fields.

Atomistic modeling of hydrogen embrittlement at grain boundaries of Mg

Magnesium is a competitive candidate material for engineering lightweight structures and biomedical degradable scaffolds. However, it often suffers unpredictably sudden failure in atmospheric and physiological environments. The prevailing viewpoints have indicated that the failure is closely related to hydrogen. So far, the relevant hydrogen-induced damage mechanisms are still of significant controversy. Building an Mg-H atomic system and conducting molecular dynamics (MD) simulations, this study quantitatively investigates the possibility of hydrogen segregation at grain boundaries (GBs) and reveals the trend of critical energy release rate (CERR) for fracture at the matrix and GBs with increasing hydrogen concentration of single-crystal and polycrystalline systems. The results show that hydrogen tends to segregate at GBs due to GB energy providing more trapping sites. The CERRs for cracking both at the matrix crystal planes and GBs significantly decrease with increasing hydrogen concentration owing to metallic bond weakening, and GBs become more brittle than crystal planes. In the systems without hydrogen, there is a higher tensile strain at fracture, the growth of the free surface is usually accompanied by dislocation emission, and the cracks can even propagate along the migrated GBs with a higher misorientation angle, resulting in an uneven fracture surface with void coalescence features. The tensile stress-strain curves of the systems with high hydrogen concentration exhibit a significant low-stress rapid unloading characteristic. As the hydrogen concentration increases, the dislocation density decreases significantly and the free surface rapidly grows along the hydrogen-distributed crystal planes or GBs, resulting in a smooth fracture surface with cleavage features.

Sintering behavior, lattice vibrational characteristics and dielectric properties of B-site ion substituted BaWO4 ceramics for LTCC applications

The influences of Mo6+ substitution at the B-site of scheelite structure on the sintering character, microstructures, lattice vibrational characteristics, and dielectric properties of BaW1-xMoxO4 (x = 0.10–0.30) ceramics were studied in detail in this paper. The sintering temperature of BaW1-xMoxO4 ceramics was effectively reduced to less than 950 °C through forming a scheelite solid solution. The densification and the quality factor (Q×f) of BaW1-xMoxO4 ceramics were also enhanced compared with pure BaWO4 ceramic. Raman spectroscopy confirmed that the dielectric constant (εr) was highly correlated with molecular polarizability, and the Q×f was strongly dependent on the symmetric stretching bond of [WO4] tetrahedron. Oxygen bond valence was one of crucial parameters for modulating the temperature coefficient of resonant frequency (τf). Interestingly, the BaW0.75Mo0.25O4 ceramic sintered at 910 °C exhibited favorable microwave dielectric properties of εr = 9.44, Q×f = 46,820 GHz (@12.5 GHz), and τf = −69.2 ppm/°C. Meanwhile, the BaW0.75Mo0.25O4 ceramic had stupendous dielectric properties in low-frequency band: εr = 17.5 and dielectric loss (tanδ) = 2.2×10−4 (@10 MHz). In addition, there was good chemical compatibility between BaW0.75Mo0.25O4 ceramic and silver electrodes. These findings evidence that BaW1-xMoxO4 ceramics are competitive candidates in LTCC technology.

Copper Paste Printed Paper‐Based Dual‐Band Antenna for Wearable Wireless Electronics

AbstractWearable wireless electronics is becoming a significant research area because of the unique features of this technology. Within this field printed antennas are the key electrical component accomplishing the signal transmission and energy harvesting tasks and at the same these antennas need to be lightweight, environmentally friendly, safe to wear, and easy to conform. Currently, the majority of available paper‐based antennas are designed for RFID, sensing, UWB, WLAN, and medical applications, with just a few being utilized in wearable applications, particularly for wireless body area network (WBAN). Furthermore, few studies have been conducted on the usage of printable copper conductive materials and low‐temperature plasma technique for the fabrication of such antennas. This study demonstrates the realization of a dual‐band paper‐based wearable antenna by screen‐printing of a plasma‐sintered conductive copper paste. The copper paste, composed of 51 wt% solid particles, can easily produce desired conductive patterns on photo paper after printing and a subsequent plasma sintering, with a good adhesion. The antenna designed on photopaper operates in the frequency bands of 1.73–2.55 GHz and 7.66–8.89 GHz. Free‐space simulation and measurement results reveal that the antenna exhibits stable radiation performance in the targeted WBAN (2.4–2.4835 GHz) and X uplink (7.9–8.4 GHz) frequency bands, together with low profile, excellent conformality and acceptable SAR values on the body and no electronic waste formed after disposal, making it a competitive candidate for usage in wearable wireless electronics.

A High Capacity p‐Type Organic Cathode Material for Aqueous Zinc Batteries

AbstractP‐type organic cathode materials typically exhibit high redox potentials and fast redox kinetics, presenting broad application prospects in aqueous zinc batteries (AZBs). However, most of the reported p‐type organic cathode materials exhibit limited capacity (<100 mAh g−1), which is attributable to the low mass content ratio of oxidation‐reduction active functional groups in these materials. Herein, we report a high‐capacity p‐type organic material, 5,12‐dihydro‐5,6,11,12‐tetraazatetracene (DHTAT), for aqueous zinc batteries. Both experiments and calculation indicate the charge storage of DHTAT mainly involves the adsorption/desorption of ClO4− on the −NH− group. Benefitting from the high mass content ratio of the −NH− group in DHATA molecule, the DHATA electrode demonstrates a remarkable capacity of 224 mAh g−1 at a current density of 50 mA g−1 with a stable voltage of 1.12 V. Notably, after 5000 cycles at a high current density of 5 A g−1, DHTAT retains 73 % of its initial capacity, showing a promising cycling stability. In addition, DHTAT also has good low‐temperature performance and can stably cycle at −40 °C for 4000 cycles at 1 A g−1, making it a competitive candidates cathode material for low‐temperature batteries.

A High Capacity p-Type Organic Cathode Material for Aqueous Zinc Batteries.

P-type organic cathode materials typically exhibit high redox potentials and fast redox kinetics, presenting broad application prospects in aqueous zinc batteries (AZBs). However, most of the reported p-type organic cathode materials exhibit limited capacity (<100 mAh g-1), which is attributable to the low mass content ratio of oxidation-reduction active functional groups in these materials. Herein, we report a high-capacity p-type organic material, 5,12-dihydro-5,6,11,12-tetraazatetracene (DHTAT), for aqueous zinc batteries. Both experiments and calculation indicate the charge storage of DHTAT mainly involves the adsorption/desorption of ClO4 - on the -NH- group. Benefitting from the high mass content ratio of the -NH- group in DHATA molecule, the DHATA electrode demonstrates a remarkable capacity of 224 mAh g-1 at a current density of 50 mA g-1 with a stable voltage of 1.12 V. Notably, after 5000 cycles at a high current density of 5 A g-1, DHTAT retains 73 % of its initial capacity, showing a promising cycling stability. In addition, DHTAT also has good low-temperature performance and can stably cycle at -40 °C for 4000 cycles at 1 A g-1, making it a competitive candidates cathode material for low-temperature batteries.

Intralayer/Interlayer Codoping Stabilizes Polarity Modulation in 2D Semiconductors for Scalable Electronics.

2D semiconductors show promise as a competitive candidate for developing future integrated circuits due to their immunity to short-channel effects and high carrier mobility at atomic layer thicknesses. The inherent defects and Fermi level pinning effect lead to n-type transport characteristics in most 2D semiconductors, while unstable and unsustainable p-type doping by various strategies hinders their application in many areas, such as complementary metal-oxide-semiconductor (CMOS) devices. In this study, an intralayer/interlayer codoping strategy is introduced that stabilizes p-type doping in 2D semiconductors. By incorporating oppositely charged ions (F and Li) with the intralayer/interlayer of 2D semiconductors, remarkable p-type doping in WSe2 and MoTe2 with air stability up to 9 months is achieved. Notably, the hole mobility presents a 100-fold enhancement (0.7 to 92 cm2 V-1 s-1) with the codoping procedure. Structural and elemental characterizations, combined with theoretical calculations validate the codoping mechanism. Moreover, a CMOS inverter and more complex logic functions such as NOR and XNOR, as well as large-area device arrays are demonstrated to showcase its applications and scalability. These findings suggest that stable and straightforward intralayer/interlayer codoping strategy with charge-space synergy holds the key to unlocking the potential of 2D semiconductors in complex and scalable device applications.

Self-assembled nanoflower-mediated interfacial polymerization through tunable intra- and inter-layer channels to boost total heat exchange performance

Total heat exchange membranes (THEMs) are vital for minimizing energy consumption and enhancing indoor air quality in energy recovery ventilation (ERV) systems. Manipulating the surface morphology of polyamide (PA) membranes via nanofiller-mediated interfacial polymerization is key to advancing total heat recovery performance. This study presented the fabrication of PA thin-film nanocomposite (TFN) membranes by integrating self-assembled poly(amic acid-imide) nanoflowers (P(AA-I)-NFs) with intertwined nanosheets into the organic phase. This facile approach effectively eliminated nonselective interphase voids and defects, owing to the superior polymer affinity of the organic nanoflowers. The finely tuned intra- and inter-layer channels within P(AA-I)-NFs significantly impacted monomer mass transfer, facilitated the shuttle effect, expanded the interfacial polymerization zone, and led to the formation of a rougher, thicker PA layer with enhanced surface area. The optimized P(AA-I)-NFs/PA TFN membranes exhibited outstanding performance, including CO₂ permeability of 0.51 GPU, water vapor permeability of 656.59 GPU, and an enthalpy exchange efficiency of 71.47 %, surpassing the trade-off limitations typically observed in commercial and other advanced THEMs. These findings underscored the potential of P(AA-I)-NFs-mediated TFN membranes as highly competitive candidates for next-generation ERV systems.

New family of two-dimensional A2B2C5 single-layer with high carrier mobilities and excellent conversion efficiency for solar cells

Screening high-performance two-dimensional (2D) materials with desirable direct band gaps and high mobility has attracted great interest due to their excellent application in 2D field effect transistors. Herein, we predicted a new family of nine-atomic A2B2C5 (A = Mg, Ba; B= Al, Ga, and In, C = S, Se) single-layer using first-principles calculations. The results indicate that the energies of this A2B2C5 single-layer are slightly lower than that of exfoliated single-layer Mg2Al2S5. Furthermore, most of the A2B2C5 single-layers host not only direct band gaps but also outstanding electron mobilities (up to ∼103 cm2V−1s−1), revealing a desirable range of near-infrared to visible light absorption. Importantly, single-layer Ba2Al2Se5 and Mg2Ga2Se5 are good donor materials, the corresponding Ba2Al2Se5/HfS2 and Mg2Ga2Se5/InS type-II heterostructures exhibit promising power conversion efficiencies of 22.3 % and 19.8 %, respectively. Our work provides some competitive A2B2C5 candidate single-layers for applying high-performance solar cells.

Dual-layer broadband encoding spectrometer: enhanced encoder basis orthogonality and spectral detection accuracy.

Spectrometer miniaturization has become a significant trend driven by the demand for distributed and continuous spectral sensing. Broadband encoding spectrometers, which utilize broadband encoder arrays to extract spectral features and algorithms to reconstruct spectra, are among the most competitive candidates for high-performance miniaturized spectrometers. Enhancing the spectral feature extraction capability of these broadband encoders is essential for improving spectrometer performance. However, the strategies and approaches for optimizing these encoders are not yet well-defined. This study analyzes the effectiveness of improving the basis orthogonality of the encoders for their optimization and proposes a dual-layer broadband encoder structure to implement this optimization strategy. The designed dual-layer broadband encoders consist of vertically stacked quantum dot encoders and TiO2/SiO2 encoders, with the corresponding basis being mixed Gaussian. Simulation experiments demonstrate that the proposed dual-layer broadband encoder structure significantly improves the encoders' basis orthogonality, leading to enhanced spectral detection accuracy of the spectrometer constructed with these dual-layer encoders. Experimental fabrication of the dual-layer encoders confirms their physical feasibility and basis orthogonality enhancement.

Highly Efficient and Reversible Carbon Dioxide Capture by Carbanion-Functionalized Ionic Liquids.

Due to the active unstable nature of carbon anions, it is challenging to develop carbanion-functionalized ionic liquids (ILs) for efficient and reversible carbon dioxide (CO2) capture. Here, a series of carbanion-based ILs with large conjugated structures were designed and a promising system was achieved through tuning the nucleophilicity of carbanions and screening the cation. The ideal carbanion-functionalized IL trihexyl(tetradecyl)phosphonium N,N-diethycyanoacetoamide ([P66614][DECA]) showed equimolar chemisorption of CO2 ( up to 0.98 mol CO2/mol IL) under ambient pressure and excellent absorption rate. What's more, the combined CO2 can be released easily, leading to excellent reversibility due to high stability of anion conjugated structures. More importantly, the presence of water had negligible effect on the absorption capacity, which makes it potential to be applied to the CO2 capture in industrial flue gas. The chemisorption mechanism of the carbanion and CO2 was confirmed by spectroscopic investigations and DFT calculations, where carboxylic acid product was formed through proton transfer after the carbanions reacted with CO2. Considering that high capacity, quick rate as well as excellent reversibility, these carbanion-functionalized ILs should certainly represent competitive candidates for further scale up and practical application in CO2 capture.

Design of the Single Heterogeneous Quantum Dot Lasers Emitting 4 Wavelengths Using Combination‐Grating Technology

AbstractMulti‐wavelength light sources are crucial for high‐bandwidth silicon photonic chips. In this paper, a single heterogeneous quantum dot distributed feedback (DFB) laser emitting 4 wavelengths using the combination‐grating technology is designed. To the best of the knowledge, this is the first heterogeneously integrated quantum dot DFB laser that lases stable multi‐wavelength in a single cavity. When the etching depth, etching width, and total length of gratings are 100 , 550 nm, and 1 000 µm, respectively, 4‐wavelength with 1297.01 , 1303.38 , 1309.74 , and 1316.11 nm are obtained by varying the grating period from 196 to 199 nm with the spacing of 1 nm. Compared to the conventional DFB laser arrays, the DFB laser units are significantly reduced by 3/4 while maintaining the same number of output wavelengths. Additionally, by optimizing the λ/4 phase‐shift position and the duty cycle of gratings, the output power at the front‐end of the 4‐wavelength laser is significantly improved. Specifically, the ratio of the output power from the front‐end and rear‐end of the laser increases from the conventional 1.00 to 2.51. This work provides a competitive candidate for multi‐wavelength, high‐performance, and large‐scale silicon‐based light sources used in data centers, lidar, and component detection.

Dense nine elemental high entropy diboride ceramics with unique high temperature mechanical and physical properties

Due to their huge composition space and superior performance characteristics, high entropy borides have garnered great interest in many fields, particularly where their high-temperature performances at high temperatures are critical. Herein, we first discovered that dense (Ti1/9Zr1/9Hf1/9Nb1/9Ta1/9V1/9Cr1/9Mo1/9W1/9)B2 (HEB9) ceramics prepared at 1850 °C showed an exceptionally low temperature coefficient of electrical resistivity (4.28 × 10−4 K−1), which is ∼38% of that of (Ti1/5Zr1/5Hf1/5Nb1/5Ta1/5)B2 (HEB5) and nearly an order of magnitude lower than those of previously reported ZrB2 and ZrB2-30 vol% SiC ceramics. Their mechanical, thermophysical properties at elevated temperatures were also investigated systematically. Although the thermal conductivity of HEB9 increased with elevated temperatures, it remained at a very low level (∼29 W/(m·K)) at 1273 K, nearly half that of HEB5. Interestingly, it is found that the thermal conduction of HEB9 and HEB5 was mainly contributed by electrons, suggeting their thermal conductivity could be roughly estimated from corresponding electrical conductivity values. Moreover, HEB9 exhibited a geometrically necessary dislocation density over 30 times greater than HEB5, likely contributing to its higher Vickers hardness and unique physical properties. Notably, the flexural strength of HEB9 at 1600 °C was even improved to 650.0 ± 86.3 MPa, compared to the value (559.7 ± 36.7 MPa) at room temperature without degradation, which was comparable to that of HEB5, although thermodynamic calculations indicated a lower melting point of HEB9 and grain boundary softening was occurred in HEB9 at higher temperatures. The excellent mechanical, electrical and thermophysical properties of HEB9 at elevated temperatures make it a competitive candidate for various high-temperature applications.