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Supertetragonal BaZrS: A promising perovskite sulphide with giant ferroelectricity and low band gap

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Science China(Physics,Mechanics & Astronomy) 2024年

作者： Menglu Li Sa Zhang Chenhan Liu xiaotao zu Liang Qiao Haiyan Xiao School of Physics University of Electronic Science and Technology of China College of Mathematics and Physics Chengdu University of Technology Micro-and Nano-scale Thermal Measurement and Thermal Management Laboratory Ministry of Education Key Laboratory of Numerical Simulation of Large-Scale Complex Systems School of Energy and Mechanical Engineering Nanjing Normal University

Over the past century, ferroelectricity has offered exciting opportunities for fundamental research and device ***, most of the discovered excellent ferroelectrics are oxide materials with large band gaps, limiting their potential for optoelectronics applications. Here using first-principles calculations we identify a new narrow-gap ferroelectric beyond oxides,i.e., ferroelectric perovskite sulphide BaZrS3. Under large compressive strains, BaZrS3can be stabilized into a unique supertetragonal phase with an extraordinary polarization of 67.16 μC/cm2, which is even stronger than that of conventional oxide ferroelectrics. Excitingly, the supertetragonal BaZrS3exhibits a direct narrow band gap of 1.2 eV and excellent electronic properties. Based on the chemical bonding analysis, we attribute the formation of supertetragonal phase to charge re-ordering in which the π bond overlap along the long ?Zr-S? bond completely vanishes and the antibonding states of the σ bond appear below the Fermi level. Our work provides a conceptual strategy for designing new ferroelectrics for electronic and photovoltaic applications.

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Optimization for epitaxial fabrication of infinite-layer nickelate superconductors

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Frontiers of physics 2024年第3期19卷 61-69页

作者： Minghui Xu Yan Zhao Xiang Ding Huaqian Leng Shu Zhang Jie Gong Haiyan Xiao xiaotao zu Huiqian Luo Ke-Jin Zhou Bing Huang Liang Qiao School of Physics University of Electronic Science and Technology of ChinaChengdu 610054China Beijing Computational Science Research Center Beijing 100193China Diamond Light Source Harwell CampusDidcot OX110DEUnited Kingdom Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China Songshan Lake Materials Laboratory Dongguan 523808China

The discovery of nickelates superconductor creates exciting opportunities to unconventional superconductivity. However, its synthesis is challenging and only a few groups worldwide can obtain samples with zero-resistance. This problem becomes the major barrier for this field. From plume dynamics perspective, we found the synthesis of superconducting nickelates is a complex process and the challenge is twofold, i.e., how to stabilize an ideal infinite-layer structure Nd_(0.8)Sr_(0.2)NiO_(2), and then how to make Nd_(0.8)Sr_(0.2)NiO_(2) superconducting? The competition between perovskite Nd_(0.8)Sr_(0.2)NiO_(3) and Ruddlesden−Popper defect phase is crucial for obtaining infinite-layer structure. Due to inequivalent angular distributions of condensate during laser ablation, the laser energy density is critical to obtain phase-pure Nd_(0.8)Sr_(0.2)NiO_(3). However, for obtaining superconductivity, both laser energy density and substrate temperature are very important. We also demonstrate the superconducting Nd_(0.8)Sr_(0.2)NiO_(2) epitaxial film is very stable in ambient conditions up to 512 days. Our results provide important insights for fabrication of superconducting infinite-layer nickelates towards future device applications.

关键词： nickelate superconductivity infinite-layer plasma condensate plume dynamics

Review on the temperature memory effect in shape memory alloys

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International Journal of Smart and Nano Materials 2011年第3期2卷 101-119页

作者： Zhiguo Wang xiaotao zu Yongquing Fu Department of Applied Physics University of Electronic Science and Technology of ChinaChengdu610054China Thin Film Centre Scottish Union of Physics Alliance(SUPA)University of West of ScotlandPaisleyPA12BE UK

Shape memory alloys(SMAs)are well known for their unique shape memory effect(SME)and superelasticity(SE)*** SME and SE have been extensively investigated in past decades due to their potential use in many applications,especially for smart *** unique effects of the SME and SE originate from martensitic transformation and its reverse *** from the SME and SE,SMAs also exhibit a unique property of memorizing the point of interruption of martensite to parent phase *** a reverse transformation of a SMA is arrested at a temperature between reverse transformation start temperature(As)and reverse transformation finish temperature(Af),a kinetic stop will appear in the next complete transformation *** kinetic stop temperature is a‘memory’of the previous arrested *** unique phenomenon in SMAs is called temperature memory effect(TME).The TME can be wiped out by heating the SMAs to a temperature higher than *** TME is a specific characteristic of the SMAs,which can be observed in TiNi-based and Cu-based *** can also occur in the R-phase ***,the TME in the R-phase transformation is much weaker than that in the martensite to parent *** decrease of elastic energy after incomplete cycle on heating procedure and the motion of domain walls have significant contributions to the *** this paper,the TME in the TiNi-based and Cu-based alloys including wires,slabs and films is characterized by electronic-resistance,elongation and DSC *** mechanism of the TME is discussed.

关键词： temperature memory effect shape memory alloys

Ab initio study of the effects of helium on the mechanical properties of different erbium hydrides

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Communications in Theoretical Physics 2021年第5期73卷 111-117页

作者： Mingwen Zhang Li Li Zhezhen Zhao Jinlan Nie xiaotao zu Hongxiang Deng School of Physics University of Electronic Science and TechnologyChengdu 610054China

Although rare-earth metals have increasingly received attention for use in the storage and transportation of the tritium used in nuclear fusion reactions,they still face great challenges,such as the effect of helium on the mechanical properties of different erbium *** this work,first principles are used to study the mechanical properties(elastic constants,Young's modulus,transverse shear modulus and bulk modulus)of different erbium hydrides exposed to *** Young's modulus,the transverse shear modulus and the bulk modulus are given based on the elastic constants calculated according to first *** is found that the mechanical properties of all three erbium hydrides decrease in the presence of helium,and the decline of the mechanical properties of ErH_3 is the most *** explain the reason for the decrease in the mechanical properties,the densities of the states of erbium hydrides are *** the calculations,helium embrittlement is not found and the ductility of the erbium hydrides improves following the production of helium at the helium concentrations considered in this work.

关键词： ab initio calculation Er hydrides helium mechanical properties

Band degeneracy enhanced thermoelectric performance in layered oxyselenides by first-principles calculations

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npj Computational Materials 2021年第1期7卷 158-170页

作者： Ning Wang Menglu Li Haiyan Xiao Zhibin Gao Zijiang Liu xiaotao zu Sean Li Liang Qiao School of Physics University of Electronic Science and Technology of ChinaChengduChina Department of Physics National University of SingaporeSingaporeRepublic of Singapore Department of Physics PhysicsLanzhou City UniversityLanzhouChina School of Materials University of New South WalesSydneyAustralia

Band degeneracy is effective in optimizing the power factors of thermoelectric(TE)materials by enhancing the Seebeck *** this study,we demonstrate this effect in model systems of layered oxyselenide family by the density functional theory(DFT)combined with semi-classical Boltzmann transport *** transport performance of layered LaCuOSe and BiCuOSe are fully *** results show that due to the larger electrical conductivities caused by longer electron relaxation times,the n-type systems show better TE performance than p-type systems for both LaCuOSe and ***,the conduction band degeneracy of LaCuOSe leads to a larger Seebeck coefficient and a higher optimal carrier concentration than n-type BiCuOSe,and thus a higher power *** optimal figure of merit(ZT)value of 1.46 for n-type LaCuOSe is 22%larger than that of 1.2 for n-type *** study highlights the potential of wide band gap material LaCuOSe for highly efficient TE applications,and demonstrates that inducing band degeneracy by cations substitution is an effective way to enhance the TE performance of layered oxyselenides.

关键词： degeneracy selenide layered

Chelating agents role on phase formation and surface morphology of single orthorhombic YMn_2O_5 nanorods via modified polyacrylamide gel route

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Science China Chemistry 2014年第3期57卷 402-408页

作者： WANG ShiFa ZHANG ChuanFei SUN GuangAi CHEN Bo XIANG Xia DING QingPing zu xiaotao School of Physical Electronics University of Electronic Science and Technology of China Institute of Nuclear Physics and Chemistry China Academy of Engineering Physics

YMn2O5nanorods were synthesized through a modified polyacrylamide gel *** synthesis strategy in this work is based on a sol-gel process using a polyacrylamide gel method in which oxalic acid,citric acid or tartaric acid is employed as the chelating *** the gel routes,oxalic acid was used as a carboxyl chelating agent,while citric acid or tartaric acid was a carboxyl and hydroxyl chelating *** as-prepared samples were characterized by means of techniques such as X-ray powder diffraction(XRD)measurement,thermogravimetric analysis(TG),differential scanning calorimetry analysis(DSC),Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS),thermal expansion measurement and field-emission scanning electron microscopy(SEM)*** was found that oxalic acid is the best chelating agent with Y(NO3)3·6H2O and Mn(CH3COO)2·4H2O as precursors to prepare a single orthorhombic YMn2O5nanorods at 1000°*** electron microscope observation shows that the morphology of YMn2O5powders is significantly dependent on the chelating *** peaks(single orthorhombic YMn2O5nanorods)at 642,600,573,546,521,493,486,468,448 and 400cm?1were observed from FTIR *** phase,surface morphology and chelation mechanisms of YMn2O5samples have been discussed on the basis of the experimental results.

关键词： YMn2O5 chelating agent thermal expansion nanorods

Improvement of tribological behavior of a Ti-Al-V alloy by nitrogen ion implantation

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Rare Metals 2006年第z1期25卷 309-314页

作者： LIU Yanzhang zu xiaotao QIU Shaoyu HUANG Xinquan Department of Applied Physics University of Electronic Science and Technology of China Chengdu 610054 China National Key Laboratory for Nuclear Fuel and Materials P.O. Box 436(4) Chengdu 610041 China Department of Applied Physics University of Electronic Science and Technology of China Chengdu 610054 China National Key Laboratory for Nuclear Fuel and Materials P.O. Box 436(4) Chengdu 610041 China National Key Laboratory for Nuclear Fuel and Materials P.O. Box 436(4) Chengdu 610041 China

The tribological properties especially wear and hardness of a Ti-Al-V alloy with nitrogen implantation (energy 60 keV) were investigated. The implantation was carried out at fluences range from 1×1016 to 4×1017 ions/cm2. Glancing angle X-ray diffraction (GAXRD) and X-ray photoelectron spectroscopy (XPS) analyses were performed to obtain surface characterization of the implanted sample. The unimplanted and implanted samples were also annealed at 600 ℃ in order to understand the influence of annealing on the tribological properties of Ti-Al-V. The hardness shows significant improvement at the higher fluence. After annealing at 600 ℃, the friction coefficient exhibits a relative decrease for the nitrogen-implanted samples. In addition, the wear rates of the implanted samples exhibits a great decrease after annealing at 600 ℃. Nature of the surface and reason for the variation and improvement in wear resistance were discussed in detail.

关键词： nitrogen ion implantation Ti-Al-V alloy phase formation tribological properties

First-principles study of He point-defects in HCP rare-earth metals

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Science China(Physics,Mechanics & Astronomy) 2011年第5期54卷 827-830页

作者： YANG LI CHEN RuCheng PENG ShuMing LONG XingGui WU ZhongCheng GAO Fei zu xiaotao Department of Applied Physics University of Electronic Science and Technology of China Chengdu 610054 China Institute of Nuclear Physics and Chemistry China Academy of Engineering Physics Mianyang 621900 China Pacific Northwest National Laboratory P. O. Box 999 Richland WA 99352 USA

He defect properties in Sc, Y, Gd, Tb, Dy, Ho, Er and Lu were studied using first-principles calculations based on density functional theory. The results indicate that the formation energy of an interstitial He atom is smaller than that of a substitutional He atom in all hcp rare-earth metals considered. Furthermore, the tetrahedral interstitial position is more favorable than an octahedral position for He defects. The results are compared with those from bcc and fcc metals.

关键词： first-principles rare-earth metals helium

Insight into the growth behaviors of MoS_(2)nanograins influenced by step edges and atomic structure of the substrate

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Nano Research 2022年第8期15卷 7646-7654页

作者： Shuangyue Wang Ni Yang Mengyao Li Ji Zhang Ashraful Azam Yin Yao xiaotao zu Liang Qiao Peter Reece John Stride Jack Yang Sean Li School of Materials Science and Engineering UNSW SydneyNSW 2052Australia School of Physics University of Electronic Science and Technology of ChinaChengdu 610054China School of Physics UNSW SydneyNSW 2052Australia School of Chemistry UNSW SydneyNSW 2052Australia

The step edges and intrinsic atomic structure of single-crystal substrate play a critical role in determining the growth pathways of transition metal dichalcogenide(TMD)grains,particularly whether the TMDs will grow into wafer-scale single-crystal or anisotropic ***,we investigate the growth behaviours of the MoS_(2)nanograins on(0001)and()sapphire *** one hand,the step edges formed on the(0001)surface after thermal treatment are found to promote the macroscopic aggregation of MoS_(2)nanograins and to form unidirectional large triangular islands along with thesteps in the annealing process,while on the pristine(0001)surface,the MoS_(2)nanograins grow into a random network-like ***,oxygen treatment on the substrate can further enhance the growth of MoS_(2)*** electron microscopy and fast Fourier transform patterns reveal that the substrate could modulate the orientation of MoS_(2)nanograins during their growing *** the other hand,the MoS_(2)nanograins on the surface could self-assemble into one-dimensional nanoribbons due to the strong structural anisotropy of the *** addition,the ratio of Raman intensities for peaks that correspond to the and A1g phonon modes shows a linear relationship with the grain size due to the change of the“phonon confinement”.Moreover,new peaks located at 226 and 280 cm−1 can be observed in the off-resonant and resonant Raman spectra for the MoS_(2)nanograin samples,respectively,which can be attributed to the scatterings from the edges of as-fabricated MoS_(2)nanostructures.

关键词： MoS_(2)nanograins growth behaviors step edges atomic structure Raman spectra evolution UV-vis absorption