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Facile synthesis of samarium and cerium doped double perovskite cobaltite with enhanced dielectric response

Journal of Rare Earths 2024年第7期42卷 1317-1327,I0005页

作者： Yasir Abbas M.Kamran M.Anis-ur-Rehman applied Thermal physics Laboratory Department of PhysicsCOMSATS University IslamabadIslamabad 45550Pakistan

The investigation of Sm-Ce doping on structure,conduction,and dielectric response of Bi_(2)Ca_(2-2x)Sm_(x)CexCoO_(6)(x=0.000,0.025,0.050,0.075)(BCSCCO)are *** the specimens were synthesized by a facile synthesis technique named the co-precipitation route.X-ray diffraction(XRD)reveals that BCSCCO crystallizes into one phase with space group P21/*** crystallite size,dislocation density,lattice parameters,lattice strain,unit cell volume,and bulk density were determined using XRD *** structural properties of Bi_(2)Ca_(2)CoO_(6)were examined using calculations based on the density functional *** and experimental values discrepancy is less than 1%.A scanning electron microscope was used for performing a microstructural *** SEM images demonstrate the homogeneous distribution of grains with a range of sizes(0.054-0.090μm).The alternating current(ac)conductivity,dielectric permittivity,and tangent loss were also studied as a function of frequency(20 Hz-3 MHz)at different temperatures(100-500℃).All synthesized samples were examined using non-linear Debye's function to determine their spreading factor and relaxation *** specimen with the lowest crystallite size(∼23 nm)exhibits a high dielectric permittivity(∼3.80×10^(6)).The conduction mechanism was examined in the studied samples with the use of Jonscher's power *** power law indicates that the BCSCCO(x=0.000,0.025)follows correlated barrier hopping,whereas the x=0.050 and 0.075 compositions follow non-overlapping polaron *** studied specimen Bi_(2)Ca_(1.9)0Sm_(0.05)0Ce_(0.05)_(0)CoO_(6)with the highest density(∼5.65 g/cm^(3))displays a high electrical conductivity(∼46.1 S/cm).These findings correspond to those published for ceramics made from calcium cobaltite using solid-state reactions(5.0-26.0 S/cm).

关键词： Bismuth calcium samarium cerium cobaltite (BCSCCO) Spreading factor Conduction mechanism Rare earths

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On-chip integrated GeSe_(2)/Si vdW heterojunction for ultravioletenhanced broadband photodetection,imaging,and secure optical communication

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Nano Research 2024年第7期17卷 6544-6549页

作者： Zhiman Zhou Kunxuan Liu Di Wu Yunrui Jiang Ranran Zhuo Pei Lin Zhifeng Shi Yongtao Tian Wei Han Longhui Zeng Xinjian Li School of physics and microelectronics Key Laboratory of Material Physics Ministry of EducationZhengzhou UniversityZhengzhou 450052China department of Electrical and Computer Engineering University of California San DiegoLa JollaCalifornia 92093USA Institute of microelectronics and Integrated Circuits School of MicroelectronicsHubei UniversityWuhan 430062China

Broadband photodetection,spanning from ultraviolet(UV)to infrared(IR),is pivotal in diverse technological domains including astronomy,remote sensing,environmental monitoring,and medical ***,current commercially available broadband photodetectors,predominately based on conventional narrow-bandgap semiconductors,exhibit limited sensitivity in the UV *** limitation,stemming from the significant energy disparity between the semiconductor bandgap and UV photon,narrows their application ***,we report an innovative approach involving the in-situ van der Waals(vdW)integration of two-dimensional(2D)GeSe_(2)layers onto a Si *** process yields a high-quality GeSe_(2)/Si vdW heterojunction device,which features a broad response range covering from UV to near-IR(NIR)with a greatly-enhanced sensitivity in the UV *** device possesses high responsivities of 325 and 533.4 mA/W,large detectivities of 1.24×10^(13)and 2.57×10^(13)Jones,and fast response speeds of 20.6/82.1 and 17.7/81.0μs under 360 and 980 nm,***,the broadband image sensing and secure invisible optical communication capabilities of the GeSe_(2)/Si heterojunction device are *** work provides a viable approach for UV-enhanced broadband photodetection technology,opening up new possibilities and applications across various scientific and technological domains.

关键词： germanium diselenide van der Waals(vdW)integration ultraviolet enhanced broadband photodetection imaging

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Nonlinear interaction of head-on solitary waves in integrable and nonintegrable systems

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Chinese physics B 2024年第5期33卷 480-487页

作者：张树甜刘世鲲矫滕菲孙敏胡凤兰黄德财 department of applied physics Nanjing University of Science and TechnologyNanjing 210094China

This study numerically investigates the nonlinear interaction of head-on solitary waves in a granular chain(a nonintegrable system)and compares the simulation results with the theoretical results in fluid(an integrable system).Three stages(the pre-in-phase traveling stage,the central-collision stage,and the post-in-phase traveling stage)are identified to describe the nonlinear interaction processes in the granular *** nonlinear scattering effect occurs in the central-collision stage,which decreases the amplitude of the incident solitary *** with the leading-time phase in the incident and separation collision processes,the lagging-time phase in the separation collision process is *** asymmetrical nonlinear collision results in an occurrence of leading phase shifts of time and space in the post-in-phase traveling *** next find that the solitary wave amplitude does not influence the immediate space-phase shift in the granular *** space-phase shift of the post-in-phase traveling stage is only determined by the measurement position rather than the wave *** results are reversed in the *** increase in solitary wave amplitude leads to decreased attachment,detachment,and residence times for granular chains and *** the immediate time-phase shift,leading and lagging phenomena appear in the granular chain and the fluid,*** results offer new knowledge for designing mechanical metamaterials and energy-mitigating systems.

关键词： integrable system nonintegrable system granular chain solitary wave

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Molecular Chaperone-Dependent Polymer Translocation through Nanopores: The Effects of Chaperone Concentration and Chaperone-Polymer Interaction

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Chinese Journal of Polymer Science 2024年第1期42卷 125-132,I0011页

作者： Chang-Sheng Zuo Kang Wang Li-Zhen Sun Ting-Ting Sun department of physics Zhejiang University of Science and TechnologyHangzhou 310023China department of applied physics Zhejiang University of TechnologyHangzhou 310014China

The polymer translocation through a nanopore from a donor space(or named cis side) to a receiver space(trans side) in the chaperone-induced crowded environment has attracted increasing attention in recent years due to its significance in biological systems and technological applications. In this work, we mainly focus on the effects of chaperone concentration and chaperone-polymer interaction on the polymer translocation. By assuming the polymer translocation to be a quasi-equilibrium process, the free energy F of the polymer can be estimated by Rosenbluth-Rosenbluth method and then the translocation time τ can be calculated by Fokker-Plank equation based on the obtained free energy landscape. Our calculation results show that the translocation time can be controlled by independently tuning the chaperone concentration and chaperone-polymer interaction at the cis side or the trans side. There exists a critical chaperone-polymer attraction ε~*=-0.2 at which the volume exclusion and interaction effects of the chaperone can balance each other. Additionally, we also find that at large chaperone-polymer attraction, the translocation time is mainly governed by the diffusion coefficient of the polymer.

关键词： Polymer translocation Rosenbluth-Rosenbluth method Fokker-Plank equation Free energy landscapes

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Emerging direct current triboelectric nanogenerator for high-entropy mechanical energy harvesting

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Science China(Technological Sciences) 2024年第5期67卷 1297-1316页

作者： CHEN Jie GUO RuiLong GUO HengYu College of physics and Electronic Engineering Chongqing Normal UniversityChongqing 401331China department of applied physics Chongqing UniversityChongqing 401331China

In the era of the Internet of Things(IoT),the provision of sustainable power to distributed,mobile,and low-power-consumption electronic devices is a critical *** overcome this challenge,the triboelectric nanogenerator(TENG),a highly efficient high-entropy mechanical energy harvesting device,was developed in *** device enables the direct conversion of irregular and low-frequency mechanical energy into pulsed alternating current(AC)***,the incompatibility of most electronic devices with AC signals necessitates rectifier circuits or generators that deliver direct current(DC)*** recent years,DC-TENGs have undergone extensive development,achieving significant milestones in various application fields while also facing crucial challenges that require *** this review,three categories of DC-TENG devices with distinct operating mechanisms are comprehensively explored:multiphase coupling,mechanical rectification,and air *** typical structures and working mechanisms are thoroughly discussed,and specific output performance limitations,along with corresponding optimization strategies,are ***,the applications of DC-TENGs in various scenarios are ***,the challenges faced by DC-TENGs and potential solutions are analyzed to guide further advancements in this technology.

关键词： TENG direct current working mechanisms output performance limitations optimization strategies

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Phase Transition in a Dense Swarm of Self-Propelled Bots

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Fluid Dynamics & Materials Processing 2024年第8期20卷 1785-1798页

作者： Dmitry Bratsun Kirill Kostarev applied physics department Perm National Research Polytechnic UniversityPerm614990Russia

Swarms of self-organizing bots are becoming important elements in various technical systems,which include the control of bacterial cyborgs in biomedical applications,technologies for creating new metamaterials with internal structure,self-assembly processes of complex supramolecular structures in disordered media,*** this work,we theoretically study the effect of sudden fluidization of a dense group of bots,each of which is a source of heat and follows a simple algorithm to move in the direction of the gradient of the global temperature *** show that,under certain conditions,an aggregate of self-propelled bots can fluidize,which leads to a second-order phase *** bots’program,which forces them to search for the temperature field maximum,acts as an effective buoyancy *** a consequence,one can observe a sudden macroscopic circulation of bots from the edge of the group to its center and back again,which resembles classical Rayleigh-Benard thermal *** the continuum approximation,we have developed a mathematical model of the phenomenon,which reduces to the equation of a self-gravitating porous disk saturated with an incompressible fluid that generates *** derive governing equations in the Darcy-Boussinesq approximation and formulate a nonlinear boundary value *** exact solution to the linearized problem for infinitesimal perturbations of the base state is obtained,and the critical values of the control parameter for the onset of the bot circulation are *** we apply weakly nonlinear analysis using the method of multiple time *** found that as the number of bots increases,the swarm exhibits increasingly complex patterns of circulation.

关键词： Active matter collective behavior self-organization convection

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Exploring one material for dual applications:A red-emitting Mg2GeO4:Eu3+ nanophosphor for future generation energy efficient WLEDs and dosimetric applications

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Journal of Rare Earths 2024年第10期42卷 1835-1845页

作者： Akshay Arjun G.P.Darshan S.C.Sharma H.Nagabhushana D.V.Sunitha H.B.Premkumar department of physics Faculty of Mathematical and Physical SciencesM.S.Ramaiah University of Applied Sciences Jain University C.N.R.Rao Centre for Advanced Materials Tumkur University School of applied Sciences (physics) REVA University

The envisaged design and developme nt of individual mate rials to excavate a broader spectrum of desired properties and offer multiple applications are highly *** this in mind,a series of forsterite-structured Mg2GeO4:Eu3+（1 mol%-9 mol%） nanophosphors was synthesized via a solution combustion method using oxalyl dihydrazide as a *** X-ray diffraction patterns confirm the orthorhombic crystal system with a Puma space *** results clearly show irregularly shaped cluster-like structures with aggregation of the *** diffuse reflectance spectra,the optical energy band gap of the Mg2GeO4:Eu3+（1 mol%-9 mol%） nanophosphors was estimated and obtained to be～4.12-4.32 *** photoluminescence emission spectra exhibit intense peaks at ～579,589,610,661,and 707 nm,which are due to characteristic5D0→7F0,5D0→7F1,5Do→7F2,5D0→7F3and5D0→7F4transitions of Eu3+ions,*** Commission International de L'Eclairage color coordinates are gradually tuned from pale red（0.5980,0.4012） to a pure red（0.6385,0.3611） *** glow peaks showcase excellent super-linear response at low doses of γ-irradiations,indicating that the prepared phosphor can be used in thermoluminescent personal dosimetry which is a biological tissue *** aforementioned results demonstrate that the prepared Mg2GeO4:Eu3+（1 mol%-9 mol%） nanophosphors are considered an excellent candidate for dual applications,i.e.,red component in future generation white-light-emitting diodes（WLEDs） and personal dosimetric applications.

关键词： Dosimetry Nanophosphors Photoluminescence Photometric properties Rare earths Thermoluminescence

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Selective nano-buckling improves the performance of graphene logic transistors

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National Science Review 2024年第2期11卷 95-96页

作者： Tong Yang Ming Yang department of applied physics The Hong Kong Polytechnic University Research Centre for Nanoscience and Nanotechnology The Hong Kong Polytechnic University

The massive integration of silicon-based transistors into modern electronic devices greatly increases power consumption and heat generation/dissipation[1]. In this concern, transistors based on atomically-thin graphene that exhibit high electric and thermoelectric conductivities with negligible contact resistance,

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Induced magneto-conductivity in a two-nodeWeyl semimetal under Gaussian random disorder

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Chinese physics B 2024年第9期33卷 566-574页

作者： Chuanxiong Xu Haoping Yu Mei Zhou Xuanting Ji department of applied physics China Agricultural UniversityBeijing 100083China department of applied Mechanics China Agricultural UniversityBeijing 100083China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China

Measuring the magneto-conductivity induced from impurities may help determine the impurity distribution and reveal the structure of a Weyl semimetal *** verify this,we utilize the Gaussian random disorder to simulate charged impurities in a two-node Weyl semimetal model and investigate the impact of charged impurities on magneto-conductivity in Weyl *** first compute the longitudinal magnetic conductivity and find that it is positive and increases proportionally with the parameter governing the Gaussian distribution of charged impurities,suggesting the presence of negative longitudinal *** we consider both the intra-valley and inter-valley scattering processes to calculate the induced transverse magneto-conductivity in the *** findings indicate that both inter-valley and intravalley scattering processes play important roles in the transverse *** locations of Weyl nodes can also be determined by magneto-conductivity *** is possible if the magnetic field strength and the density of charged impurities are ***,the measurement of magnetic conductivity may reveal the distribution of charged impurities in a given sample once the locations of the Weyl nodes have been *** findings can aid in detecting the structure of a Weyl semimetal sample,enhancing comprehension of magnetotransport in Weyl semimetals and promoting the development of valley electronics.

关键词： Weyl semimetal inter-valley scattering magneto-conductivity

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Simple chemical synthesis and isotropic negative thermal expansion in MHfF_(6)(M=Ca,Mn,Fe,and Co)

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Nano Research 2024年第3期17卷 2195-2203页

作者： Yongqiang Qiao Sen Zhang Peixian Zhang Juan Guo Andrea Sanson Xi Zhen Kaiyue Zhao Qilong Gao Jun Chen Key Laboratory of Materials physics of Ministry of Education and School of Physics and MicroelectronicsZhengzhou UniversityZhengzhou 450052China department of physics and Astronomy University of PadovaPadova I-35131Italy Beijing Advanced Innovation Center for Materials Genome Engineering Department of Physical ChemistryUniversity of Science and Technology BeijingBeijing 100083China

The rapid progress of modern technologies has accelerated the prominence of thermal expansion mismatch between materials,and tunable thermal expansion materials will be a powerful safeguard against this ***,isotropic MHfF_(6)(M=Ca,Mn,Fe,and Co)compounds with tunable thermal expansion have been produced via a low-cost synthetic method and *** utilizing temperature dependent X-ray diffraction(XRD)and Raman spectroscopy,combined with first principles calculations,it was revealed that the transverse thermal vibrations of the F atoms are dominated by low-frequency phonons with negative Grüneisen parameters and are therefore the origin of the negative thermal expansion(NTE).Very interestingly,with the increase of the M atomic number,the metal…F atomic linkages become stiffer,reducing the number of vibrational modes with negative Grüneisen parameters,so that the strong NTE can be gradually adjusted to moderate NTE and to near zero thermal *** present study achieves the tunable thermal expansion in a new compound family and shed light on the internal mechanism from the perspective of lattice vibrational dynamics.

关键词： negative thermal expansion fluorides chemical synthesis nanosheet structure first principles calculations

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