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学者姓名：刘文凤
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Abstract ：
In the present study, pure and donor-acceptor co-doped Ba0.675Sr0.325TiO3 (BST) ceramics were prepared by the conventional solid-state reaction method. La was fixed as the donor dopant at A-site while Mn, Cr, and Fe were selected as the acceptor dopants at B-site. The effect of acceptor dopants on the microstructure and electrical properties of BST ceramics was investigated systematically from the view of different ionic radius and electro-negativity. Enhanced dielectric tunability and reduced dielectric loss could be realized by co-doping, resulting in a significant improvement in the figure of merit (FOM). The optimum tunable properties were obtained in Mn-La co-doped ceramics with the dielectric tunability of 85.1%, the dielectric loss of 0.0018, and the FOM of 472. Such results could be attributed to the smaller ionic radius and weaker electronegativity of Mn. Compared to pure BST ceramics with the FOM of 40, co-doped BST ceramics exhibited great potential for tunable device applications. The breakdown strength (BDS) of BST ceramics was also studied in this work. Improved breakdown strength by co-doping took better stability for its applications under applied electric field.
Keyword ：
BST ceramics Co-doping Figure of merit Tunable device
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| GB/T 7714 | Liu, Wenfeng , Zhao, Yi , Jin, Yihang et al. Enhanced dielectric tunability and reduced dielectric loss in various donor-acceptor co-doped Ba0.675Sr0.325TiO3 ceramics [J]. | MATERIALS CHEMISTRY AND PHYSICS , 2022 , 291 . |
| MLA | Liu, Wenfeng et al. "Enhanced dielectric tunability and reduced dielectric loss in various donor-acceptor co-doped Ba0.675Sr0.325TiO3 ceramics" . | MATERIALS CHEMISTRY AND PHYSICS 291 (2022) . |
| APA | Liu, Wenfeng , Zhao, Yi , Jin, Yihang , Kong, Fanyi , Gao, Jinghan , Li, Shengtao . Enhanced dielectric tunability and reduced dielectric loss in various donor-acceptor co-doped Ba0.675Sr0.325TiO3 ceramics . | MATERIALS CHEMISTRY AND PHYSICS , 2022 , 291 . |
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Abstract ：
In the present study, (Ba0.65Sr0.35)(1-x)LaxTi1-xFexO3(x = 0, 0.0025, 0.005, 0.01) ceramics were designed and prepared by the conventional solid-state reaction method. The microstructures and electrical properties of La/Fe co-doped Ba0.65Sr0.35TiO3 ceramics were investigated. Enhanced dielectric tunability and reduced dielectric loss were achieved in this system. The acceptor dopant Fe3+ was used to lower dielectric loss while the donor dopant La3+ was added to improve dielectric tunability. The optimum tunable properties took place at x = 0.0025 with the dielectric tunability = 78.8% and the dielectric loss = 0.0040. The figure of merit (FOM) was improved to 197, about five times that of pure BST. The breakdown strength (BDS) enhanced from 59.9 kV/cm to 111.4 kV/cm by La3+ and Fe3+ dopant, which promoted the stability of BST ceramics under high applied electric field. In conclusion, excellent tunable properties and improved breakdown strength made it possible for the La/Fe co-doped BST ceramics to be promising for tunable microwave applications. (C) 2022 Published by Elsevier B.V.
Keyword ：
Breakdown strength BST ceramics Co-doping Tunable properties
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| GB/T 7714 | Liu, Wenfeng , Zhao, Yi , Jin, Yihang et al. Enhanced dielectric tunability and reduced dielectric loss in the La/Fe co-doped Ba0.65Sr0.35TiO3 ceramics [J]. | JOURNAL OF ALLOYS AND COMPOUNDS , 2022 , 901 . |
| MLA | Liu, Wenfeng et al. "Enhanced dielectric tunability and reduced dielectric loss in the La/Fe co-doped Ba0.65Sr0.35TiO3 ceramics" . | JOURNAL OF ALLOYS AND COMPOUNDS 901 (2022) . |
| APA | Liu, Wenfeng , Zhao, Yi , Jin, Yihang , Kong, Fanyi , Gao, Jinghan , Li, Shengtao . Enhanced dielectric tunability and reduced dielectric loss in the La/Fe co-doped Ba0.65Sr0.35TiO3 ceramics . | JOURNAL OF ALLOYS AND COMPOUNDS , 2022 , 901 . |
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Abstract ：
In the present study, BaTi(1-x)MxO3 (x = 0.005, 0.01, 0.015; M is Mn, Fe, and Co) ceramics were prepared by the conventional solid-state reaction method. Four distinct and independently addressed memory states were experimentally obtained based on the double hysteresis loop, which was achieved by acceptor doping in BaTiO3 ceramics. Moreover, this study indicated that for acceptor-doped BaTiO3 ceramics, larger electronegativity and smaller ionic radius of acceptor ions benefitted the more significant memory effect and better fatigue resistance. All these results could provide a promising solution for multi-state memory applications. (c) 2022 Published by Elsevier B.V.
Keyword ：
Acceptor-doping BaTiO3 ceramics Fatigue resistance Memory effect
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| GB/T 7714 | Liu, Wenfeng , Jin, Yihang , Zhao, Yi et al. The effect of acceptor dopant on the memory effect of BaTiO3 ceramics [J]. | JOURNAL OF ALLOYS AND COMPOUNDS , 2022 , 928 . |
| MLA | Liu, Wenfeng et al. "The effect of acceptor dopant on the memory effect of BaTiO3 ceramics" . | JOURNAL OF ALLOYS AND COMPOUNDS 928 (2022) . |
| APA | Liu, Wenfeng , Jin, Yihang , Zhao, Yi , Kong, Fanyi , Gao, Jinghan , Zhang, Lei et al. The effect of acceptor dopant on the memory effect of BaTiO3 ceramics . | JOURNAL OF ALLOYS AND COMPOUNDS , 2022 , 928 . |
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Abstract ：
In the present study, an industrially viable ceramics fabrication way based on solid-state reaction method-semisolution method was used to improve the dielectric and ferroelectric properties of acceptor-donor co-doped BaTiO3 ceramics. Unlike the conventional solid-state reaction method, additives in the semi-solution method were introduced in the form of the aqueous solution rather than oxide powders. Experiment results show that higher peak dielectric constant epsilon(max) (140-150%), larger maximum polarization P-max (24 mu C cm-(2)), and less apparent aging phenomena were achieved by the semi-solution method. A comprehensive microscopic analysis was carried out to explore the origin of property enhancement. Results show that enhanced properties could be ascribed to the higher level of compositional homogeneity and lower content of oxygen vacancies. This study provides a new method to control aging phenomena and achieve property enhancement in acceptor-donor codoped ceramics. Moreover, this simple and cost-effective method may also find its application in other extensivedoped ceramics.
Keyword ：
Aging phenomena Barium titanate Defect chemistry Ferroelectrics Hybrid-doping Solid-state reaction method
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| GB/T 7714 | Gao, Jinghan , Liu, Wenfeng , Zhang, Lei et al. Enhanced dielectric and ferroelectric properties of the hybrid-doped BaTiO3 ceramics by the semi-solution method [J]. | CERAMICS INTERNATIONAL , 2021 , 47 (11) : 15661-15667 . |
| MLA | Gao, Jinghan et al. "Enhanced dielectric and ferroelectric properties of the hybrid-doped BaTiO3 ceramics by the semi-solution method" . | CERAMICS INTERNATIONAL 47 . 11 (2021) : 15661-15667 . |
| APA | Gao, Jinghan , Liu, Wenfeng , Zhang, Lei , Kong, Fanyi , Zhao, Yi , Li, Shengtao . Enhanced dielectric and ferroelectric properties of the hybrid-doped BaTiO3 ceramics by the semi-solution method . | CERAMICS INTERNATIONAL , 2021 , 47 (11) , 15661-15667 . |
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Abstract ：
Flexible micro-pyramidal capacitive pressure sensors provide a high-level tunability, showing fascinating implications in various applications, such as advanced healthcare, protheses, and smart robots. In this work, analytical models for capacitive pressure sensors are reported based on micro-pyramidal electrodes and dielectrics, which are confirmed by both finite element simulations and existing experimental results. The proposed models can be used to predict the pressure response in a wide dynamic range, which enables to efficiently analyze the pressure range, linearity, and multiple regimes of sensitivity for designing devices. Moreover, neural networks are introduced to approximate the pressure responses, and, in turn, to inversely design the parameters of the pressure sensors with a desired pressure response. The machine-learning-assisted design is able to find multiple designed parameters for the customization purpose, manifesting itself a powerful approach to customize the sensor performance.
Keyword ：
flexible capacitive pressure sensor inverse design machine learning micropyramids neural networks
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| GB/T 7714 | Ma, Chao , Li, Gang , Qin, Longhui et al. Analytical Model of Micropyramidal Capacitive Pressure Sensors and Machine-Learning-Assisted Design [J]. | ADVANCED MATERIALS TECHNOLOGIES , 2021 , 6 (12) . |
| MLA | Ma, Chao et al. "Analytical Model of Micropyramidal Capacitive Pressure Sensors and Machine-Learning-Assisted Design" . | ADVANCED MATERIALS TECHNOLOGIES 6 . 12 (2021) . |
| APA | Ma, Chao , Li, Gang , Qin, Longhui , Huang, Weicheng , Zhang, Hongrui , Liu, Wenfeng et al. Analytical Model of Micropyramidal Capacitive Pressure Sensors and Machine-Learning-Assisted Design . | ADVANCED MATERIALS TECHNOLOGIES , 2021 , 6 (12) . |
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Abstract ：
In order to satisfy demands of cable insulation for nuclear power, a low-smoke, halogen-free flame retardant and better cryogenic property insulation was prepared. The effect of thermal-oxidative aging on the dielectric properties was researched in this paper. The changes of chemical structure and thermal-oxidative stability caused by aging were characterized by Fourier transform infrared spectroscopy and a differential scanning calorimeter. The results showed that, the oxidative-induced stability reduced as complex products accumulated during aging. The dielectric properties including polarity, conductivity and breakdown at different aging stages were measured. For comparison, tensile testing was performed. The parameters related to conductivity changed notably, and were comparable with the changes in mechanical properties. © 2020 by the authors.
Keyword ：
Cable sheathing Chemical stability Dielectric properties Differential scanning calorimetry Fourier transform infrared spectroscopy Insulating materials Nuclear fuels Smoke Tensile testing Thermal insulation
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| GB/T 7714 | Chi, Xiaohong , Li, Jianxi , Ji, Minzun et al. Thermal-oxidative aging effects on the dielectric properties of nuclear cable insulation [J]. | Materials , 2020 , 13 (10) . |
| MLA | Chi, Xiaohong et al. "Thermal-oxidative aging effects on the dielectric properties of nuclear cable insulation" . | Materials 13 . 10 (2020) . |
| APA | Chi, Xiaohong , Li, Jianxi , Ji, Minzun , Liu, Wenfeng , Li, Shengtao . Thermal-oxidative aging effects on the dielectric properties of nuclear cable insulation . | Materials , 2020 , 13 (10) . |
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Abstract ：
In the present study, we designed a new system, Ba(Ti0.99-1.25xMn0.01Nbx)O3 (x = 0.5%, 1.0%, 1.25%, 1.5%), to improve the energy storage properties of BaTiO3–based ceramics. Here the acceptor dopant Mn was introduced to enhance the maximum polarization Pmax while reducing the remnant polarization Pr by inducing aging phenomena. The donor dopant Nb was added to make the hysteresis loop slimmer and slender through ‘softening’ effect. And the ratio of acceptor and donor was adjusted to modify the energy storage properties by modulating the shape of hysteresis loop. Results showed that an enhancement of 76% over pure BaTiO3 in recoverable energy storage density (Wrec) has been achieved in hybrid-doped samples, accompanied by a high energy conversion efficiency (η) up to 86%. Hereinto, donor-dominant samples doped with 1% Mn and 1.25% Nb exhibited the highest Wrec and η with excellent thermal stability. This study proved the feasibility of enhancing the energy storage properties by hybrid doping and may provide a new viewpoint for later studies. © 2020 Elsevier B.V.
Keyword ：
Barium titanate Conversion efficiency Energy storage Hysteresis Hysteresis loops Manganese Niobium Polarization
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| GB/T 7714 | Liu, Wenfeng , Gao, Jinghan , Zhao, Yi et al. Significant enhancement of energy storage properties of BaTiO3-based ceramics by hybrid-doping [J]. | Journal of Alloys and Compounds , 2020 , 843 . |
| MLA | Liu, Wenfeng et al. "Significant enhancement of energy storage properties of BaTiO3-based ceramics by hybrid-doping" . | Journal of Alloys and Compounds 843 (2020) . |
| APA | Liu, Wenfeng , Gao, Jinghan , Zhao, Yi , Li, Shengtao . Significant enhancement of energy storage properties of BaTiO3-based ceramics by hybrid-doping . | Journal of Alloys and Compounds , 2020 , 843 . |
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Abstract ：
Grain size and its spatial distribution are the crucial issues in the study of advanced materials with a grain-grain boundary structure. It not only implies the grain growth mechanism of those materials, but also determines most of their macroscopic properties, such as mechanical strength, current conduction, ageing and so on. Therefore, it is of importance to clarify the grain size distribution (GSD) in ZnO-based varistor ceramics, a key protection element against overvoltage. In the present paper, a new approach based on the log-normal distribution was proposed to analyze the variation of GSD along the thickness direction of two commercial ZnO varistors. It is found that GSD follows log-normal distribution rather than commonly used normal distribution. In addition, with the proposed grain size, i.e., averaged log-normal grain size (dLN) and most probable grain size (dmax), the variation of GSD along the thickness direction was clearly revealed, which exhibited quite different behavior depending on the samples. With the probability plot, the microscopic uniformity is carefully analyzed and discussed. It is proposed that probability plots can be divided into three regions, representing large grains, grains whose sizes follow the lognormal rule and small grains, respectively. With the proposed method, it is possible to obtain more quantitative information, which is of significance for the further development of ZnO-based varistor ceramics and other advanced materials. © 2018 IEEE.
Keyword ：
Grain-grain boundaries Grain growth mechanisms Grain size distribution Log-normal distribution Macroscopic properties Probability plot Quantitative information Zno-based varistor ceramics
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| GB/T 7714 | Zhang, Lei , Yu, Chuan , Zhang, Le et al. A Statistical Approach for Effectively Analyzing the Grain Size Distribution Along the Thickness Direction in Commercial ZnO-Based Varistor Ceramics [C] . 2018 . |
| MLA | Zhang, Lei et al. "A Statistical Approach for Effectively Analyzing the Grain Size Distribution Along the Thickness Direction in Commercial ZnO-Based Varistor Ceramics" . (2018) . |
| APA | Zhang, Lei , Yu, Chuan , Zhang, Le , Liu, Wenfeng , Wu, Kangning , Li, Shengtao et al. A Statistical Approach for Effectively Analyzing the Grain Size Distribution Along the Thickness Direction in Commercial ZnO-Based Varistor Ceramics . (2018) . |
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Abstract ：
© 2018 Polypropylene (PP), is one of the most widely used dielectric materials in electrical industry, especially in power capacitors and power cables. The requirement of higher electrical properties of PP by the rapid development of power system made the nanocomposite to be a promising solution to modify PP based dielectrics. In this review, we focused on the electrical properties and systematically gave an overview of PP based nanocomposite researches for power equipment application in recent years. We categorized the electrical properties into breakdown strength, dielectric permittivity, and long-term electrical performance, and summarized the correlations between enhanced properties and nanofiller types both experimentally and theoretically. Based on the achieved approaches, prospects for the future research on PP based nanocomposite was proposed, which may provide a worth-considering direction for the future work.
Keyword ：
Dielectric Nanocomposite Polypropylene
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| GB/T 7714 | Liu, Wenfeng , Cheng, Lu , Li, Shengtao . Review of electrical properties for polypropylene based nanocomposite [J]. | Composites Communications , 2018 , 10 : 221-225 . |
| MLA | Liu, Wenfeng et al. "Review of electrical properties for polypropylene based nanocomposite" . | Composites Communications 10 (2018) : 221-225 . |
| APA | Liu, Wenfeng , Cheng, Lu , Li, Shengtao . Review of electrical properties for polypropylene based nanocomposite . | Composites Communications , 2018 , 10 , 221-225 . |
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Abstract ：
Polypropylene (PP) contains promising application prospects in thermoplastic cables for high voltage direct current (HVDC) power transmission because of its outstanding thermal and dielectric properties. However, the problem of poor toughness and space charge has restricted the application of pure PP in HVDC cables. In this paper, polyolefin elastomer (POE) and nano-silica were blended thoroughly and added into a PP mixture by a melting method. Scanning electron microscopy (SEM) was employed to observe the dispersion of POE and nanoparticles. Thermal properties were characterized by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Mechanical properties were evaluated by tensile tests. The elastomeric properties of composites were improved as the dispersed POE could transfer and homogenize external mechanical forces. DC breakdown results showed that the fail strength of composite with 10 phr POE and 1 phr nano-silica was obviously enhanced. The pulsed electro-acoustic (PEA) results showed that the injection and accumulation of space charge was increased by the introduction of POE, while it was restrained by the collective effect caused by nano-silica filling. X-ray diffraction (XRD) spectrograms showed that secondary ordered structures existed in the composites of PP, POE, and nano-silica, and that the ordered structure around the nanoparticles contributed to the enhancement of breakdown strength. The mechanical and dielectric properties were modified synergistically, which made the modified PP a propitious insulation material for HVDC cables.
Keyword ：
dielectric properties elastomer blending mechanical properties nano-silica filling PP-based dielectric
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| GB/T 7714 | Chi, Xiaohong , Cheng, Lu , Liu, Wenfeng et al. Characterization of Polypropylene Modified by Blending Elastomer and Nano-Silica [J]. | MATERIALS , 2018 , 11 (8) . |
| MLA | Chi, Xiaohong et al. "Characterization of Polypropylene Modified by Blending Elastomer and Nano-Silica" . | MATERIALS 11 . 8 (2018) . |
| APA | Chi, Xiaohong , Cheng, Lu , Liu, Wenfeng , Zhang, Xiaohong , Li, Shengtao . Characterization of Polypropylene Modified by Blending Elastomer and Nano-Silica . | MATERIALS , 2018 , 11 (8) . |
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