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SrGa_(12)O_(19):The first low-ε_(r) Ga-based microwave dielectric ceramic with anomalous positiveτ_(f)

Journal of advanced Ceramics 2024年第9期13卷 1432-1441页

作者： Yang Yang Weishuang Fang Huixing Lin Jie Li Huaicheng Xiang Ying Tang Lei Li Liang Fang Guangxi Universities Key Laboratory of Non-ferrous Metal Oxide Electronic Functional Materials and Devices and Guangxi Key Laboratory of Optical and Electronic Materials and DevicesCollege of Materials Science and EngineeringGuilin University of TechnologyGuilin 541004China Key Laboratory of Inorganic Functional Material and Devices Shanghai Institute of CeramicsChinese Academy of SciencesShanghai 200050China Laboratory of Dielectric Materials School of Materials Science and EngineeringZhejiang UniversityHangzhou 310058China

Dielectric ceramics with low permittivity(ε_(r)),high quality factor(Q×f),and near-zero resonant frequency(τ_(f))in the microwave bands are key materials used in fifth/sixth-generation(5G/6G)telecommunication,whileτ_(f) of most low-εr microwave dielectric ceramics is relatively *** this work,the first low-εr Ga-based ceramic SrGa_(12_O_(19) with an anomalous positiveτ_(f) was reported,and the causes of the positiveτ_(f),intrinsic polarization,and loss mechanism were systematically studied.X-ray diffraction(XRD)and transmission electron microscopy(TEM)revealed that the SrGa_(12_O_(19) ceramic formed a pure hexagonal magnetoplumbite structure with spinel blocks and rock-salt blocks stacked along the crystallographic *** sintered at 1430℃,it possessed the optimal microwave dielectric properties of a lowεr of 14.46,high Q×f of 64,705 GHz,and exceptional positiveτ_(f) of+55.7 ppm/℃,along with a low linear thermal expansion coefficient(αL)of 11.617 ppm/℃.The large positive deviation betweenεr andεr(C–M)of 45.31%resulted from the rattling effect of atoms in the rock-salt *** unique positiveτ_(f)(+55.7 ppm/℃)was governed by the rattling effect,resulting in a positiveταm(the temperature coefficient of ion polarizability)of 8.489 ppm/℃ and a large negative temperature coefficient of permittivity(τε)of−132.864 ppm/℃.Phillips–Vechten–Levine(P–V–L)chemical bond theory revealed greater contributions of the spinel block to bond ionicity(fi,52.95%),permittivity(ε,55.15%),bond energy(E,56.87%),and lattice energy(U,74.88%)than those of the rock-salt *** intrinsic dielectric properties were analyzed using infrared(IR)reflectivity *** favorable performance of the SrGa_(12)O_(19) ceramic indicated that it is a novelτ_(f) *** selection of compounds with different structural layer combinations provides a new idea for exploring excellent microwave dielectric ceramics.

关键词： magnetoplumbite microwave dielectric properties rattling effect chemical bond theory

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Abnormal dielectric behavior of glaserite-type Ba_(3−x)Sr_(x)MgSi_(2)O_(8)solid solution

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Journal of advanced Ceramics 2025年第2期14卷 77-86页

作者： Jiaqing Yang Peng Lei Xiaoqiang Song Changzhi Yin Meng Zhang Weicheng Lei Yiyang Cai Mingfei Cheng Yaodong Liu Zihang Chen Yaqing Hu Wenzhong Lu Wen Lei School of Optical and Electronic Information Key Lab of Functional Materials for Electronic Information(B)of MOEHuazhong University of Science and TechnologyWuhan 430074China Wenzhou Key Laboratory of Microwave Communication Materials and Devices Wenzhou Advanced Manufacturing Institute of HUSTWenzhou 325035China

The temperature coefficient of the resonant frequency(τ_(f))of low-permittivity(ε_(r))microwave dielectric ceramics is required to be near 0 ppm/℃for practical ***,owing to the polarization mechanism,τ_(f)of low-ε_(r)microwave dielectric ceramics is generally ***,a novel microwave dielectric ceramic,Ba_(3−x)Sr_(x)MgSi_(2)O_(8),with an abnormal positiveτ_(f)at the applied temperature is *** this study,Sr^(2+)with a relatively small ionic radius was introduced to replace Ba^(2+),and a single-phase solid solution was formed(x>0.5).Ba_(3−x)Sr_(x)MgSi_(2)O_(8)ceramics were discussed in glaserite-type topology with space groups of P_(3)^(-)for x≤0.5,relatively high symmetry P_(3)^(-)m1 for 0.5functional theory simulation calculations revealed that the preferential occupation of Sr^(2+)ions could decrease the intrinsic formation energy and improve the microwave dielectric properties by mitigating the ionic size mismatch within the crystal *** present research offers a strategy for discovering novel microwave dielectric ceramics with abnormalτ_(f)values,which could serve as τ_(f)regulators in practical applications because of their low cost and excellent microwave dielectric properties.

关键词： microwave dielectric ceramics abnormal dielectric behavior ion size mismatch [SiO4]tetrahedra tilting phase transition density functional theory(DFT)

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Anisotropic etching mechanisms of 4H-SiC:Experimental and first-principles insights

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Journal of Semiconductors 2024年第1期45卷 42-47页

作者： Guang Yang Lingbo Xu Can Cui Xiaodong Pi Deren Yang Rong Wang Key Laboratory of Optical Field Manipulation of Zhejiang Province Department of PhysicsZhejiang Sci-Tech UniversityHangzhou 310018China State Key Laboratory of Silicon and Advanced Semiconductor Materials&School of Materials Science and Engineering Zhejiang UniversityHangzhou 310027China Institute of Advanced Semiconductors&Zhejiang Provincial Key Laboratory of Power Semiconductor Materials and Devices HangzhoIun novation CenterZhejiang UniversityHangzhou 311200China

Molten-alkali etching has been widely used to reveal dislocations in 4H silicon carbide(4H-SiC),which has promoted the identification and statistics of dislocation density in 4H-SiC single ***,the etching mechanism of 4H-SiC is limited *** this letter,we reveal the anisotropic etching mechanism of the Si face and C face of 4H-SiC by combining molten-KOH etching,X-ray photoelectron spectroscopy(XPS)and first-principles *** activation energies for the molten-KOH etching of the C face and Si face of 4H-SiC are calculated to be 25.09 and 35.75 kcal/mol,*** molten-KOH etching rate of the C face is higher than the Si *** XPS analysis and first-principles calculations,we find that the molten-KOH etching of 4H-SiC is proceeded by the cycling of the oxidation of 4H-SiC by the dissolved oxygen and the removal of oxides by molten *** faster etching rate of the C face is caused by the fact that the oxides on the C face are unstable,and easier to be removed with molten alkali,rather than the C face being easier to be oxidized.

关键词： principles alkali etching

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Demonstration of irradiation-resistant 4H-SiC based photoelectrochemical water splitting

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Journal of Semiconductors 2024年第11期45卷 74-80页

作者： Yan Pei Wenhao Geng Lingbo Xu Can Cui Xiaodong Pi Deren Yang Rong Wang Zhejiang Key Laboratory of Quantum State Control and Optical Field Manipulation Department of PhysicsZhejiang Sci-Tech UniversityHangzhou 310018China State Key Laboratory of Silicon and Advanced Semiconductor Materials&School of Materials Science and Engineering Zhejiang UniversityHangzhou 310027China Institute of Advanced Semiconductors&Zhejiang Provincial Key Laboratory of Power Semiconductor Materials and Devices HangzhouIn no-vation CenterZhejiang UniversityHangzhou 311200China

4H silicon carbide(4H-SiC)has gained a great success in high-power electronics,owing to its advantages of wide bandgap,high breakdown electric field strength,high carrier mobility,and high thermal *** the high carrier mobility and high stability of 4H-SiC,4H-SiC has great potential in the field of photoelectrochemical(PEC)water *** this work,we demonstrate the irradiation-resistant PEC water splitting based on nanoporous 4H-SiC arrays.A new two-step anodizing approach is adopted to prepare 4H-SiC nanoporous arrays with different porosity,that is,a constant low-voltage etching followed by a pulsed high-voltage *** constant-voltage etching and pulsed-voltage etching are adopted to control the diameter of the nanopores and the depth of the nanoporous arrays,*** is found that the nanoporous arrays with medium porosity has the highest PEC current,because of the enhanced light absorption and the optimized transportation of charge carriers along the walls of the nanoporous *** performance of the PEC water splitting of the nanoporous arrays is stable after the electron irradiation with the dose of 800 and 1600 k Gy,which indicates that 4H-SiC nanoporous arrays has great potential in the PEC water splitting under harsh environments.

关键词： 4H-SiC nanoporous arrays water splitting irradiation resistance photoanodes

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Oxygen-coordinated low-nucleus cluster catalysts for enhanced electrocatalytic water oxidation

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Carbon Energy 2023年第2期5卷 137-147页

作者： Jiapeng Ji Yunpeng Hou Shiyu Zhou Tong Qiu Liang Zhang Lu Ma Chao Qian Shaodong Zhou Chengdu Liang Min Ling Zhejiang Provincial Key Laboratory of Advanced Chemical Engineering Manufacture Technology College of Chemical and Biological EngineeringZhejiang UniversityHangzhouChina Jiangsu Key Laboratory for Carbon-Based Functional Materials&Devices Joint International Research Laboratory of Carbon-Based Functional Materials and DevicesInstitute of Functional Nano&Soft Materials(FUNSOM)Soochow UniversitySuzhouJiangsuChina National Synchrotron Light Source II Brookhaven National LaboratoryUptonNew YorkUSA Institute of Zhejiang University-Quzhou QuzhouChina

The oxygen evolution reaction(OER)activity of single-atom catalysts(SACs)is closely related to the coordination environment of the active *** atomic metal species bring about unique features beyond nitrogen-coordinated atomic metal species due to the fact that the M-O bond is weaker than the M-N ***,a series of metal-oxygen-carbon structured low-nucleus clusters(LNCs)are successfully anchored on the surface of multiwalled carbon nanotubes(M-MWCNTs,M=Ni,Co,or Fe)through a foolproof low-temperature gas transfer(300℃)method without any further *** morphology and coordination configuration of the LNCs at the atomic level were confirmed by comprehensive *** synthetic Ni-MWCNTs electrocatalyst features excellent OER activity and stability under alkaline conditions,transcending the performances of Co-MWCNTs,Fe-MWCNTs and RuO_(2).Density functional theory calculations reveal that the moderate oxidation of low-nucleus Ni clusters changes the unoccupied orbital of Ni atoms,thereby lowering the energy barrier of the OER rate-limiting step and making the OER process more *** study demonstrates a novel versatile platform for large-scale manufacturing of oxygen-coordinated LNC catalysts.

关键词： electrocatalytic water oxidation low-nucleus cluster low-temperature gas transfer metal-oxygen-carbon structure

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Suppressed concentration quenching and tunable photoluminescence in Eu^(2+)-activated Rb_(3)Y(PO_(4))_(2) phosphors for full-spectrum lighting

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Light(Science & Applications) 2024年第11期13卷 2688-2698页

作者： Ming Zhao Yeping Ge Yurong Li Xiaoyan Song Zhiguo Xia Xinping Zhang Institute of Information Photonics Technology School of Physics and Optoelectronic EngineeringBeijing University of TechnologyBeijing 10083China College of Materials Science and Engineering Key Laboratory of Advanced Functional MaterialsEducation Ministry of ChinaBeijing University of TechnologyBeijing 10083China State Key Laboratory of Luminescent Materials and Devices Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied TechniquesGuangdong Engineering Technology Research and Development Center of Special Optical Fiber Materials and DevicesSchool of Physics and OptoelectronicsSouth China University of TechnologyGuangzhou 510641China

Highly efficient inorganic phosphors are desirable for lighting-emitting diode light sources,and increasing the doping concentration of activators is a common approach for enhancing the photoluminescence quantum yield(PLQY).However,the constraint of concentration quenching poses a great challenge for improving the ***,we propose a fundamental design principle by separating activators and prolonging their distance in Eu^(2+)-activated Rb_(3)Y(PO_(4))_(2)phosphors to inhibit concentration quenching,in which different quenching rates are controlled by the Eu distribution at various crystallographic *** blue-violet-emitting Rb_(3)Y(PO_(4))2:xEu(x=0.1%–15%)phosphors,with the occupation of Rb1,Rb2 and Y sites by Eu^(2+),exhibit rapid luminescence quenching with optimum external PLQY of 10%due to multi-channel energy ***,as the Eu concentration increases above 20%,Eu^(2+)prefer to occupy the Rb1 and Y sites with separated polyhedra and large interionic distances,resulting in green emission with suppressed concentration quenching,achieving an improved external PLQY of 41%.Our study provides a unique design perspective for elevating the efficiency of Eu^(2+)-activated phosphors toward high-performance inorganic luminescent materials for full-spectrum lighting.

关键词： quenching lighting concentration

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Gigahertz frequency hopping in an optical phase-locked loop for Raman lasers

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Chinese Physics B 2024年第2期33卷 60-65页

作者：毛德凯税鸿冕殷国玲彭鹏王春唯周小计 State Key Laboratory of Advanced Optical Communication System and Network School of ElectronicsPeking UniversityBeijing 100871China Institute of Carbon-based Thin Film Electronics Peking UniversityTaiyuan 030012China State Key Laboratory of Quantum Optics and Quantum Optics Devices Institute of Opto-ElectronicsShanxi UniversityTaiyuan 030006China Institute of Advanced Functional Materials and Devices Shanxi UniversityTaiyuan 030031China

Raman lasers are essential in atomic physics,and the development of portable devices has posed requirements for time-division multiplexing of Raman *** demonstrate an innovative gigahertz frequency hopping approach of a slave Raman laser within an optical phase-locked loop(OPLL),which finds practical application in an atomic gravimeter,where the OPLL frequently switches between near-resonance lasers and significantly detuned Raman *** method merges the advantages of rapid and extensive frequency hopping with the OPLL’s inherent low phase noise,and exhibits a versatile range of applications in compact laser systems,promising advancements in portable instruments.

关键词： Raman lasers optical phase-locked loop frequency hopping

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Construction of ZnO@CDs@Co_(3)O_(4) sandwich heterostructure with multi-interfacial electron-transfer toward enhanced photocatalytic CO_(2) reduction

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Chinese Chemical Letters 2024年第4期35卷 147-152页

作者： Xiuzheng Deng Yi Ke Jiawen Ding Yingtang Zhou Hui Huang Qian Liang Zhenhui Kang Advanced Catalysis and Green Manufacturing Collaborative Innovation Center CNPC-CZU Innovation AllianceSchool of Petrochemical EngineeringChangzhou UniversityChangzhou 213164China Institute of Functional Nano&Soft Materials(FUNSOM) Jiangsu Key Laboratory for Carbon-Based Functional Materials&DevicesSoochow UniversitySuzhou 215123China Zhejiang Key Laboratory of Petrochemical Environmental Pollution Control National Engineering Research Center for Marine AquacultureMarine Science and Technology CollegeZhejiang Ocean UniversityZhoushan 316004China

Photocatalytic conversion of CO_(2) into small-molecule chemical feedstocks can meet the growing demand for energy and alleviate the global warming. Herein, a p-n ZnO@CDs@Co_(3)O_(4) heterojunction with sandwich structure was constructed by calcination method of self-assembled ZIF-8@CDs@ZIF-67. The ZnO@CDs@Co_(3)O_(4) with well-defined interfacial structure exhibited the significantly enhanced photocatalytic CO_(2) reduction activity, and the optimal catalyst indicated the(CO + CH_(4)) evolution rate of 214.53μmol g^(-1)h^(-1) under simulated solar light, which was superior to ZnO, Co_(3)O_(4) and binary ZnO@Co_(3)O_(4).The internal cavity, exposed active sites, multiple interfaces and constructed p-n heterojunction can facilitate the light harvesting and photoexcited electron transfer. Besides, after introduction of CDs placed in the middle layer between ZnO and Co_(3)O_(4), CDs with excellent photoelectric property further promoted charge separation and migration. This work represents an appealing strategy to construct well-defined photocatalysts for boosting CO_(2) photoreduction.

关键词： Metal-organic framework Photocatalytic CO_(2) reduction Carbon dots p-n heterojunction Sandwich heterostructure

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Dynamic tunable LWIR achromatic metalens comprising all-As_(2)Se_(3) microstructures

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Chinese Optics Letters 2024年第6期22卷 191-195页

作者： Zhihao He Bingxia Wang Zhiang Qian Kongsi Zhou Xiang Shen Yungui Ma Laboratory of Infrared Materials and Devices The Research Institute of Advanced TechnologiesKey Laboratory of Photoelectric Detection Materials and Devices of Zhejiang ProvinceNingbo UniversityNingbo 315211China State Key Laboratory of Modern Optical Instrumentation Centre for Optical and Electromagnetic ResearchCollege of Optical Science and EngineeringInternational Research Center for Advanced PhotonicsZhejiang UniversityHangzhou 310058China

In the field of long-wave infrared(LWIR) thermal imaging, vital for applications such as military surveillance and medical diagnostics, metalenses show immense potential for compact, lightweight, and low-power optical systems. However, to date, the development of LWIR broadband achromatic metalenses with dynamic tunable focus, which are suitable for both coaxial and off-axis applications, remains a large unexplored area. Herein, we have developed an extensive database of broadband achromatic all-As2Se3microstructure units for the LWIR range. Utilizing this database with the particle swarm optimization (PSO) algorithm, we have designed and demonstrated LWIR broadband achromatic metalenses capable of coaxial and off-axis focusing with three dynamic tunable states. This research may have potential applications for the design of compact, high-performance optical devices, including those with extreme depth-of-field and wide-angle imaging capabilities.

关键词： achromatic metalens long-wave infrared dynamic tunable focus

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All-fiber and self-starting Yb-doped Mamyshev oscillator based on nonlinear polarization evolution

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Chinese Optics Letters 2024年第12期22卷 74-79页

作者： Zecong Li Kai Wang Zinan Huang Qianqian Huang YanlüLin Weixi Li Zhichao Luo Chengbo Mou Key Laboratory of Specialty Fiber Optics and Optical Access Networks Shanghai Institute for Advanced Communication and Data ScienceJoint International Research Laboratory of Specialty Fiber Optics and Advanced CommunicationShanghai UniversityShanghai 200444China Key Laboratory of Space Active Opto-Electronics Technology Shanghai Institute of Technical PhysicsChinese Academy of SciencesShanghai 200083China Laboratory of Nanophotonic Functional Materials and Devices School of Information and Optoelectronic Science and EngineeringSouth China Normal UniversityGuangzhou 510006China

We experimentally demonstrate a Yb-doped all-fiber mode-locked laser based on the Mamyshev *** entire experimental setup operates only by injecting pump powers and adjusting polarization controllers(PCs),which realizes *** types of pulse patterns are observed at different pump powers and polarization states,including single pulses and up to eight-pulse bound-state *** operating wavelength of single-pulse mode-locking switching between 1072.3and 1043.1 nm can be realized by increasing the pump power while keeping the PCs in a fixed *** design can provide an attractive experimental model for all-fiber and self-starting Mamyshev oscillators.

关键词： Mamyshev oscillator Yb-doped fiber laser pulse dynamic pattern nonlinear polarization evolution

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