High Output Power Density Research Articles

Gap Confinement Effect of a Tandem Nanochannel System and Its Application in Salinity Gradient Power Generation.

As an important nanofluidic device, an artificial ion nanochannel could selectively transport ions inside its nanoconfinement space and the surface charge of the pore wall. Here, confinement effects were realized by tandem nanochannel units, which kept their cascade gaps less than 500 nm. Within these gaps, ionic conductance was governed by the surface charge density of the channel unit. Cations could be sufficiently selected and enriched within this confined space, which improves the cation transfer number of the system. Therefore, the tandem nanochannel system could greatly improve the diffusion potential and energy conversion efficiency in the salinity gradient power generation process. Poisson-Nernst-Planck equations were introduced to numerically simulate the ionic transport behavior and confirmed the experimental results. Finally, the gap confinement effect was introduced in the porous cellulose acetate membrane tandem nanochannel system, and a high output power density of 4.72 W/m2 and energy conversion efficiency of 42.22% were achieved under stacking seven channel units.

Boron Strengthened GeTe‐Based Alloys for Robust Thermoelectric Devices with High Output Power Density

AbstractHigh‐performance thermoelectric (TE) devices require not only a high figure of merit (ZT) but also mechanical strength and thermal stability. Here, a simultaneous enhancement of ZT as well as mechanical properties is obtained in GeTe‐based alloys by adding boron. This material is then assembled with n‐type CoSb3 skutterudite into TE modules. The improved ZT values result from the increase in charge carrier mobility due to the reduced interfacial barrier height. A peak ZT of 2.2 at 773 K can be achieved in Ge0.84Pb0.1Sb0.06TeB0.07, which shows a negligible change in the coefficient of thermal expansion upon the phase transition from the rhombohedral to the cubic phase, ensuring good thermal stability of the device. Resulting from the boron‐induced grain refinement and dispersion strengthening, the average compressive strength and Vickers hardness of Ge0.9Sb0.1TeB0.07 can be enhanced to ≈227 MPa and ≈202 Hv, respectively. The improved mechanical properties facilitate the assembly of devices and lower the interfacial contact resistance. As a synergy of increased ZT and mechanical strength, a high output power density of ≈1.76 W cm−2 at ΔT = 425 K and an energy conversion efficiency of 7.4% at ΔT = 477 K can be achieved in the TE modules.

Concept for Realizing High Output Power Density Thermionic Energy Convertor by Field-Assisted Thermionic Emission Using a Direct-Tunneling Metal–Insulator–Graphene Cathode

The usage of waste heat is an effective way to satisfy the great demand for energy in modern human society. A thermionic energy convertor (TEC) can directly produce electricity from thermal energy with high efficiency. However, high working temperature is one of the major challenges in TEC. In this work, a concept based on field-assisted thermionic emission (FTE) has been proposed to solve this problem. Basically, the field-assisted thermionic energy convertor (FTEC) uses a metal-insulator-graphene (MIG) structure as the cathode to produce direct-tunneling FTE current for the conversion. The fundamental performance of FTEC has been theoretically studied. The penetration field within the MIG structure that controls both the FTE current and the hot electron energy is the key for the performance optimization. By engineering the MIG cathode band structure to balance the above mentioned effects of the penetration field, the ideal efficiency of ~10% and the corresponding output power density of ~5 W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> can be obtained simultaneously under 700 K. Further comparison between FTEC and conventional TEC indicates that the output power density can be improved by at least four orders of magnitude under a mild temperature (600-700 K). These results provide a universal approach for realizing compact high output power density TEC and its combined system.

Theoretical and Experimental Studies on MEMS Variable Cross-Section Cantilever Beam Based Piezoelectric Vibration Energy Harvester.

The piezoelectric vibration energy harvester (PVEH) based on the variable cross-section cantilever beam (VCSCB) structure has the advantages of uniform axial strain distribution and high output power density, so it has become a research hotspot of the PVEH. However, its electromechanical model needs to be further studied. In this paper, the bidirectional coupled distributed parameter electromechanical model of the MEMS VCSCB based PVEH is constructed, analytically solved, and verified, which laid an important theoretical foundation for structural design and optimization, performance improvement, and output prediction of the PVEH. Based on the constructed model, the output performances of five kinds of VCSCB based PVEHs with different cross-sectional shapes were compared and analyzed. The results show that the PVEH with the concave quadratic beam shape has the best output due to the uniform surface stress distribution. Additionally, the influence of the main structural parameters of the MEMS trapezoidal cantilever beam (TCB) based PVEH on the output performance of the device is theoretically analyzed. Finally, a prototype of the Aluminum Nitride (AlN) TCB based PVEH is designed and developed. The peak open-circuit voltage and normalized power density of the device can reach 5.64 V and 742 μW/cm3/g2, which is in good agreement with the theoretical model value. The prototype has wide application prospects in the power supply of the wireless sensor network node such as the structural health monitoring system and the Internet of Things.

Performance enhancement of a beam and slot interconnector for anode-supported SOFC stack

This study proposes a novel interconnector, termed beam and slot interconnector (BSI), for the anode-supported planar solid oxide fuel cell (SOFC). A detailed comparative investigation is conducted on various transport characteristics and electrical performance of the SOFC stacks with conventional straight channel interconnectors (SCIs) or with novel interconnectors. Results show that the peak power density of a SOFC stack with BSIs is 24.8% higher than it with SCIs at 700 °C and a fuel–air flow rate of 16–40 Nml/(min·cm2). Moreover, BSI can reduce the fuel–air feeding and enhance the fuel–air utilization while maintaining high output power density. Compared with SCI, BSI promotes the gas disturbance, significantly increases the gas velocity and vorticity, and leads the gas to flow in the direction perpendicular to the channel. BSI eliminates the limitation of SCIs on gas diffusion in the electrode and transfers sufficient reactant gas into the electrode function layers for electrochemical reactions. BSI shortens the charge transfer path in SOFC and almost avoids the adverse effects of the electrode-interconnector contact resistance. Compared with the conventional SOFC stack, the novel SOFC stack with BSIs significantly reduces various overpotentials. At 700 °C and 0.5 A/cm2, the activation, concentration, and contact overpotentials are reduced by 8.5%, 47.4%, and 96.4% respectively, and the total overpotential finally drops by 20.0%. Overall, the electrical performance of the SOFC stack with novel interconnectors significantly exceeds the one with conventional interconnectors under the same operating conditions.

Identifying Parameters from Discharging and Relaxation Curves of Lithium-Ion Batteries Using Porous Electrode Theory

In order to improve the performance of Lithium-ion secondary batteries (LiBs) for electric vehicles and hybrid electric vehicles, it is very important to understand the internal transport phenomena and resistance under a high rate condition to increase power density. Especially, it is important to focus on the actual porous electrode structure, and the Li ion and electron conductivity have to be evaluated by the effective conductive path with the actual electrode material properties. Thus, the numerical simulation of electrochemical reaction and mass transport in the electrode layer are needed to design a heterogeneous porous structure which consists of active material, conductive material and binder. Then, the values of parameters in this model are essential for accuracy of it. However, some parameters cannot be measured precisely in experiment, especially, reaction rate constant, tortuosity of the separator, Li+ diffusion coefficient, and transport number in the electrolyte are treated as literature values or ex-situ results. In this study, we established a method of identifying these parameters by using experimental data in various conditions and a complex method. Further, this approach was applied to 1D LiB simulation. Fitting the experimental data of some SOC and some discharge rate conditions was carried out. Additionally, RMSE (Root Mean Square Error) to judge this fitting was evaluated. From these results, it was concluded that the parameters can be identified. In addition, with the identified parameters, the optimal electrode structure for a high-output power density cell was designed automatically.

Flexible electroactive PVDF/ZnO nanocomposite with high output power and current density

AbstractIn the present study, a lightweight and flexible polyvinylidene fluoride (PVDF)/zinc oxide (ZnO) nanocomposite was prepared using a low‐temperature phase‐inversion process. The synergetic effect of low‐temperature, phase‐inversion, and the integration of ZnO nanoparticles primes on enhancing the electroactive polar β‐phase in the nanocomposite. The transformation of the electroactive phase and its quantification were carried out using Fourier‐transform infrared spectroscopy and wide‐angle X‐ray diffraction. The PVDF/ZnO piezoelectric polymer nanocomposite was utilized for energy harvesting application that showed a better electromechanical response of ca. 69 V (peak to peak) at ~1.6 N, 250 μW/cm2 surface power density and 0.25 mA/cm2 surface current density. The fabricated piezoelectric polymer nanocomposite is a possible candidate for superior energy scavenging applications for capturing human kinematics.

Near-field thermophotovotaic devices with surrounding non-contact reflectors for efficient photon recycling.

Near-field thermophotovoltaic (TPV) power generation has been attracting increasing attention as a promising approach for efficient conversion of heat into electricity with high output power density. Here, we numerically investigate near-field TPV devices with surrounding reflectors for efficient recycling of low-energy photons, which do not contribute to the power generation. We reveal that the conversion efficiency of a near-field TPV system can be drastically increased by introducing a pair of reflectors above and below the system, especially when the two mirrors are not in contact with the emitter and absorber. In addition, we investigate the influence of non-perfect photon recycling on the TPV efficiency and reveal that near-field TPV systems are more robust against the decrease of the reflectivity of the reflectors than the far-field TPV systems.

Ultra-robust and broadband rotary hybridized nanogenerator for self-sustained smart-farming applications

The practical realization of nanogenerators for realistic applications of scavenging sustainable energy is still challenging due to their limited output performance and mechanical durability. Herein, a contactless mode triggering-based ultra-robust rotary hybridized nanogenerator (CMTUr-HNG) for efficiently harvesting wind- and water-flows in natural environments is reported. By implementing a soft magnetic-coupled triggering strategy, the hybrid electromagnetic-triboelectric nanogenerator shows high output performance under a broad range of rotational motions (50–1000 rpm) with excellent robustness. The electrospun nanofibers materials greatly improve the triboelectric performance while the electromagnetic structure is optimized by finite element method simulations. Therefore, the as-fabricated CMTUr-HNG delivers a maximum hybrid power of 40.65 mW at a matching load resistance, while triboelectric and electromagnetic generators show a high output power density of 1568 mW/kg and 386 mW/kg at 500 rpm, respectively. The robustness of CMTUr-HNG is confirmed by a durability test for 8.5 h (≈2,000,000 cycles) at 1000 rpm. As a feasible application, a self-powered wireless smart-farm monitoring system has been successfully implemented using the CMTUr-HNG, thereby demonstrating the immense potential of harvesting rotational energy for future autonomous sensing technologies. • Miniaturized hybridized (electromagnetic-triboelectric) nanogenerator for effectively harvesting rotational energy. • Soft magnetic-coupled triggering strategy for ultra-robust triboelectric nanogenerators. • High output performance under a broad range of rotational motions (50-1000 rpm). • Implementing nanofiber-based tribo-layers increase the charge density by 5.7 times. • Successful demonstration of a self-powered wireless smart-farm monitoring system.

Breathable Nanogenerators for an On-Plant Self-Powered Sustainable Agriculture System.

Building an intelligent interface between plants and the environment is of paramount importance for real-time monitoring of the health status of plants, especially promising for high agricultural yield. Although the advancement of various sensors allows automated monitoring, developing a sustainable power supply for these electronic devices remains a formidable challenge. Herein, a waterproof and breathable triboelectric nanogenerator (WB-TENG) is designed based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanofibers embedded with fluorinated carbon nanotubes (F-CNT) microspheres, which was realized by simultaneous electrospinning and electrospraying, respectively. Using carbon nanotubes (CNT) as the electrode, the WB-TENG shows micro-to-nano hierarchical porous structures and high electrostatic adhesion, exhibiting a high output power density of 330.6 μW cm-2, breathability, and hydrophobicity. Besides, the WB-TENG can be conformally self-attached to plant leaves without sacrificing the intrinsic physiological activities of plants, capable of harvesting typical environmental energy from wind and raindrops. Results demonstrate that the WB-TENG can serve as a sustainable power supply for a wireless plant sensor, enabling real-time monitoring of the health status of plants. This work realizes the concept of constructing a plant compatible TENG with environment adaptivity and energy scavenging ability, showing great potential in building a self-powered agriculture system.

Flexible and wearable piezoelectric nanogenerators based on P(VDF-TrFE)/SnS nanocomposite micropillar array

Polymer piezoelectric nanogenerators (PENGs) have attracted extensive interest in mechanical energy conversion and wearable electronics for the advantages they have to offer owing some of their characteristics, e.g., the fact that they are light weight, possess a desirable flexibility, and benefit from a high adaptability and simple large-scale manufacturing processes. In this paper, a high-performance organic flexible PENG based on a poly(vinylidene fluoride-trifluorethylene) [P(VDF-TrFE)] film doped with a SnS nanosheet (NS) micropillar array has been prepared and characterized. The piezoelectric coefficient of the P(VDF-TrFE)/SnS NSs (0.3 wt. %) nanocomposite has been greatly enhanced compared with that of the pristine P(VDF-TrFE) film, from 13 to 21 pC N−1. It also demonstrates outstanding open-circuit voltage (Voc) and short-circuit current (Isc) outputs of 17.28 V cm−2 and 0.94 μA cm−2 under the pressure of 0.5 MPa, which represents a 6-fold and 4-fold improvement, respectively, compared with what a neat P(VDF-TrFE) film was able to deliver. The device was capable of producing a high output power density of 10.69 μW cm−2 under an applied pressure of 0.5 MPa. The dramatic enhancement obtained using nanocomposite micropillar array films results from a more developed β-phase content in the organic film, the higher piezoelectric properties of SnS NSs, and the better alignment of dipoles induced by the micropillar array structure. These remarkably enhanced PENG performances seem to hold much promise for the development of wearable electronics exploiting ambient mechanical energy, thanks to its ability to produce different signals depending on the nature of the source of stimuli.

Development of Flexible Triboelectric Generators Based on Patterned Conductive Textile and PDMS Layers

A triboelectric generator (TEG) is a simple coupling combined with triboelectrification and electrostatic induction, which can convert mechanical energy into electrical energy and have the potential for self-powered device application. In this study, TEGs are fabricated consisting of a conductive textile (CT) layer (a fabric woven with polyester and stainless steel) and a polydimethylsiloxane (PDMS) layer. The CT friction layer is also used as a conductive electrode and designed with various surface morphologies, including unpatterned, dots, and lines with 1 and 2 cm spacings. Experimental results show that the TEG with an unpatterned CT layer produces an output voltage of 54.6 V and an output current of 5.46 µA. The patterned surfaces increase the effective contact area and friction effect between the CT and PDMS layers and hence enhance the output voltage and current to 94.4 V and 9.44 µA. Compared to the unpatterned CT layer, the pattern use of 1 cm spaced lines, 2 cm spaced lines, and dots improves the output voltage and current by 1.73, 1.68, and 1.24 times, respectively. Moreover, the TEG with 1 cm spaced lines generates a high output power density of 181.9 mW/m2.

Fabrication and characterization of low temperature sintered hard piezoelectric ceramics for multilayer piezoelectric energy harvesters

In this study, 0.65Pb(Zr0.465Ti0.545)O3-0.35Pb(Zn1/6Ni1/6Nb2/3)O3, doped with 3.0 mol% MnCO3 and 1.0 mol% CuO (M3.0C1.0PZT-PZNN), was investigated as a hard piezoelectric ceramic for multilayer ceramic piezoelectric energy harvesters (MLC-PEHs). These PEHs showed a high output performance that was partly ascribed to the hardening effect of MnCO3. In contrast, a single-layer ceramic piezoelectric energy harvester (SLC-PEH), containing M3.0C1.0PZT-PZNN, exhibited a higher output power density than that containing an analogous non-Mn-doped soft piezoelectric ceramic (C1.0PZT-PZNN), especially at high accelerations. In the fabricated MLC-PEH, containing an M3.0C1.0PZT-PZNN-based five-layer ceramic and a pure Ag inner electrode, no interdiffusion was observed between the electrode and the ceramic layers, and the corresponding interface was clear and smooth. This MLC-PEH, which exhibited a high output power density and a relatively large current, was used to charge a 0.22 F capacitor at its resonance frequency and an acceleration of 1.5 G, achieving a charging rate higher than that of the SLC-PEH.

In-situ alkaline pretreatment of waste activated sludge in microbial fuel cell enhanced power production

Energy recovery from waste activated sludge (WAS) by microbial fuel cell (MFC) can simultaneously address energy issue and environmental concerns. Pretreatments are vital to enhancing energy recovery and sludge reduction with WAS as power source in MFC. The commonly applied two-stage process, which separates WAS pretreatment with electricity generation, decreases the cost-effectiveness of MFC with WAS as power source. It is of great practical importance to investigate the feasibility of one-stage process for simultaneous sludge pretreatment and electricity generation. Herein, a one-stage alkaline MFC (anode chamber controlled at pH 9.0) is constructed to recover energy from in-situ alkaline pretreated WAS. Results show that alkaline MFC achieves excellent performance of electricity generation with high voltage output (0.74 V) and high power density (0.65 W m−2). The total chemical oxygen demand removal of WAS is >40%. No greenhouse gas (CH4 and CO2) are released from the alkaline MFC with WAS as power source. The enhanced electricity generation performance in the alkaline MFC is investigated through three aspects, including internal resistance, degradation of soluble organics, and shift of microbial community. This work offers a promising alternative for energy recovery with WAS as renewable power source.

Demonstration of friction-based triboelectric nanogenerator and integration in a power-balanced fully autonomous system

The deployment of IoTs and mobile objects heavily relies on batteries as power sources for integration to new applications. Alternatively, triboelectric nanogenerators (TENGs) can be seen as a promising technology by harvesting mechanical energy for powering small-scale electronics. The integration of TENGs into practical applications within a limited power requirement, is still unexplored considering its attractive properties. In this work, a state of the art multilayer integrated TENG structure with high output power density is devised compatible with practical applications to promote the technological maturity of TENGs. The proposed system consists of a sliding based TENG power source integrated to drive an e-ink™ display screen application controlled by an efficient power management unit. Through simultaneous investigation of the triboelectric power source and the application system integration focusing on power balance, an optimized self-sufficient system has been demonstrated by using a well-designed hand powered sliding motion test platform, respectively. The integrated system reaches a maximum output power density of 750 mW m −2 , adequate to drive the target application. The realization of an efficient and low cost integration with reliable power output performance showcases TENG as an attractive potential for the next generation of autonomous electronic and wireless devices. • A state-of-the-art multilayer integrated sliding based TENG structure with a high output powerdensity of 750 mW.m -2 compatible with practical applications to promote thetechnological maturity of TENGs. • Investigation on the physical phenomenon of current transfer between the electrodes has alsobeen carried out along with comprehensive analytical model. • Through simultaneous investigation of the triboelectric power source and the application systemintegration focusing on power balance, the overall system reaches a 5.2 V DC output with 7-8 human hand sliding motions, adequate to drive an electronic paper display screen.

High output power density and strong vibration durability in a modified barbell-shaped energy harvester based on multilayer Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 single crystals

Traditional piezoelectric energy harvesters are made of piezoelectric ceramics with a cantilever structure, which show a low output energy density. Thus, they are difficult to meet the requirements for self-powered electronics. Herein, we report a modified barbell-shaped piezoelectric energy harvester (BSPEH) based on two d33-mode cuboid Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 multilayer single crystal stacks (ten wafers with a thickness of 0.5 mm and d33 ∼ 1300 pC/N). Due to the electrically parallel and series connections of multilayer piezoelectric elements and the high figure-of-merit d33 × g33 of the single crystal, the maximum power density of BSPEH could reach 39.7 mW cm−3 (under an acceleration of 5 g), which is much higher than that of traditional cantilever piezoelectric energy harvesters (CPEHs), ∼0.1 mW cm−3. A maximum output voltage of 50.4 Vp–p was obtained when two crystal stacks are connected in series, and a maximum output current of 880 µA can be obtained when two crystal stacks are connected in parallel. Furthermore, the energy harvesting properties of BSPEH stay almost the same after 106 vibration cycles, while the properties of CPEH decrease 20% after 105 vibration cycles. This work indicates that BSPEH has a great potential in the application of wireless sensor networks for realizing the self-power of the equipment.

Enzymes hosted in redox-active ionically cross-linked polyelectrolyte networks enable more efficient biofuel cells.

Redox mediators are pivotal players in the electron transfer process between enzymes and electrodes. We present an alternative approach for redox mediation based on branched polyethyleneimine (BPEI) modified with an osmium complex. This redox polyelectrolyte is crosslinked with phosphate to produce colloidal particles with a diameter of ca. 1 μm, which, combined with glucose oxidase (GOx), can form electroactive assemblies through either layer by layer assembly (LbL) or one-pot drop-casting (OPDC). The addition of NaCl to these colloidal systems induces the formation of films that otherwise poorly grow, presenting an outstanding catalytic current. The system was tested as a bioanode delivering a power output of 148 μW per nmol of mediator. These results are explained in terms of the interactions of the ions with the polyelectrolyte and represent a new route for the development of bioelectrochemical devices involving redox mediators and enzymes.

1 W/mm Output Power Density for H-Terminated Diamond MOSFETs With Al2O3/SiO2Bi-Layer Passivation at 2 GHz

We have demonstrated a novel method of depositing ALD-Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /PECVD-SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> bi-layer dielectric to passive the surface channels of the hydrogen-terminated diamond (H-diamond). After Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> passivation, the surface current increased with time and then tended to be saturated. Afterwards, it became much more stable and showed a larger current than an unpassivated counterpart. The H-diamond MOSFETs were fabricated by using this bi-layer passivation structure and an extremely low Ohmic contact resistance of 0.87 Ω·mm was obtained. The H-diamond RF MOSFET with gate length of 0.45 μm achieved a high current density of -549 mA/mm and an extrinsic fT/fmax of 15/36 GHz. By load-pull measurement, a high output power density of 1.04 W/mm was obtained at frequency of 2 GHz. The results reveal that it is a promising solution for high-stable and high-power diamond transistors by using the Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> bi-layer passivation.

Design and Analysis of Gallium Nitride-Based p-i-n Diode Structure for Betavoltaic Cell with Enhanced Output Power Density.

In this work, Gallium Nitride (GaN)-based p-i-n diodes were designed using a computer aided design (TCAD) simulator for realizing a betavoltaic (BV) cell with a high output power density (Pout). The short-circuit current density (JSC) and open-circuit voltage (VOC) of the 17 keV electron-beam (e-beam)-irradiated diode were evaluated with the variations of design parameters, such as the height and doping concentration of the intrinsic GaN region (Hi-GaN and Di-GaN), which influenced the depletion width in the i-GaN region. A high Hi-GaN and a low Di-GaN improved the Pout because of the enhancement of absorption and conversion efficiency. The device with the Hi-GaN of 700 nm and Di-GaN of 1 × 1016 cm−3 exhibited the highest Pout. In addition, the effects of native defects in the GaN material on the performances were investigated. While the reverse current characteristics were mainly unaffected by donor-like trap states like N vacancies, the Ga vacancies-induced acceptor-like traps significantly decreased the JSC and VOC due to an increase in recombination rate. As a result, the device with a high acceptor-like trap density dramatically degenerated the Pout. Therefore, growth of the high quality i-GaN with low acceptor-like traps is important for an enhanced Pout in BV cell.

Preparing bulk Cu-Ni-Mn based thermoelectric alloys and synergistically improving their thermoelectric and mechanical properties using nanotwins and nanoprecipitates

Cu-Ni-Mn based alloys have long been considered as potential thermoelectric materials because of their Seebeck effect and large power factor. In this study, bulk Cu-Ni-Mn based alloys with nanostructures were prepared via melting and cryorolling, and their thermoelectric and mechanical properties were analyzed. A large number of nanotwins and nanoprecipitates were observed in the prepared alloys using transmission electron microscopy. These observations indicate that the bulk Cu-Ni-Mn alloys with nanostructures can be successfully prepared using conventional melting-solidification-rolling technology. The Cu-Ni-Mn alloy containing nanotwins exhibits a promising Seebeck coefficient of ∼ −72.8 μVK−1 and power factor of ∼11000 μWm−1K−2 at 1073 K, and thereby, a high output power density. The bulk Zr-doped Cu-Ni-Mn alloy containing nanoprecipitates and nanotwins exhibits a lower thermal conductivity of ∼32.9 Wm−1K−1 and a 37.5% higher ZT of ∼0.22 at 773 K. Enhanced mechanical properties make the Cu-Ni-Mn based alloys a promising candidate for thermoelectric application. Our discovery provides a promising strategy to improve the thermoelectric and mechanical properties of materials with high thermal conductivity through the introduction of nanotwins and nanoprecipitates.