The Experts below are selected from a list of 180 Experts worldwide ranked by ideXlab platform
Xueming Ma - One of the best experts on this subject based on the ideXlab platform.
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Fabrication of ZnO-based thick film varistors with high Potential Gradient
Rare Metals, 2010Co-Authors: Lei Ke, Dongmei Jiang, Xueming MaAbstract:ZnO-based thick film varistors have been fabricated by Y2O3 doping and low-temperature sintering, of which the sample with the best electrical properties has a high Potential Gradient value of 3159.4 V/mm. The effects of Y2O3 doping concentration and sintering temperature on the Potential Gradient of the samples were systematically investigated. The results show that the sample with the best electrical properties can be obtained by doping 0.08 mol% Y2O3 and sintering at 725°C. Under these optimum preparation conditions, the leakage current and the nonlinear coefficient are found to be 36.4 μA and 13.1. The sample with the best electrical properties has a grain size of 1.290 μm, a single grain boundary voltage of 4.08 V, a barrier height of 0.81 eV, and a depletion layer width of 10.2 nm, which are determined by thermionic emission. Small grain size with good grain boundary characteristics is beneficial to improve the electrical properties of varistors and promote the Potential Gradient.
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HIGH Potential Gradient OF ZnO VARISTORS PREPARED BY Y2O3-DOPING AND LOW-TEMPERATURE SINTERING
Modern Physics Letters B, 2009Co-Authors: Lei Ke, Dongmei Jiang, Chun-xia Wang, Xueming MaAbstract:A high Potential Gradient of ZnO varistors were fabricated by Y2O3-doping and low-temperature sintering. The value of the Potential Gradient increased to 2460.5 V/mm with the Y2O3 content of 0.08 mol% and the sintering temperature of 800°C. The effects of Y2O3-doping and sintering temperature on the electrical properties of ZnO varistors were investigated. Under the given experimental conditions, additive Y2O3 exists in the form of Y2O3 phase after sintering at 800°C. High-energy ball-milling in the early period of the experiment induced the grain refinement and realized the sintering formation at the lower temperature of 800°C. Both Y2O3-doping and low-temperature sintering restrained the ZnO grain growth and increased the Potential Gradient.
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HIGH Potential Gradient OF Y2O3-DOPED THICK FILM VARISTORS
Surface Review and Letters, 2009Co-Authors: Lei Ke, Dongmei Jiang, Xueming MaAbstract:The electrical and microstructural properties of a series of ZnO-based thick film varistors (TFVs) doped with 0.00, 0.02, 0.04, 0.06, 0.08, and 0.10 mol% Y2O3 were studied. It was found that sample doped with 0.08 mol% Y2O3 showed the highest Potential Gradient of 3159.4 V/mm with a leakage current of 36.4 μA and a nonlinear exponent of 13.1. The ZnO grain size decreased with increasing Y2O3 content, which was the origin for the increase in Potential Gradient. Raman spectra results showed that the tensile stress increased linearly with Y2O3 doping. Larger tensile stress was considered to result from the lattice distortion and inevitably influenced the grain boundary characteristics. While the Y2O3 doping concentration was beyond 0.08 mol%, the effect of residual stress on electrical properties was much more remarkable than that of grain size, leading Potential Gradient to be weakened. As a result, high Potential Gradient of ZnO-based TFVs could be obtained with Y2O3 doping concentration of 0.08 mol% and qualified as excellent candidates for high voltage varistor application.
James C Matthews - One of the best experts on this subject based on the ideXlab platform.
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the relationship between aerosol concentration and atmospheric Potential Gradient in urban environments
Science of The Total Environment, 2020Co-Authors: Matthew D Wright, James C Matthews, Hugo G Silva, Asan Bacak, Carl J Percival, Dudley E ShallcrossAbstract:Abstract Urban aerosol is a growing concern for people living within cities; aerosol have been implicated in many ill health conditions, including that of the lung and of the heart. Atmospheric Potential Gradient is a consequence of charge carried to the ionosphere through thunderstorms, and its value depends on highly electrically mobile ion concentrations, hence local conductivity of the air. Ions attach to aerosol in the atmosphere, reducing their mobility and therefore increasing the Potential Gradient, and so Potential Gradient measurements have been suggested as a proxy for aerosol measurements. Particle number count, size distribution and Potential Gradient were measured for two campaigns in Manchester, U.K., and one campaign in Bristol, U.K. Using a factor based on size distribution to account for preferential attachment at larger sizes provided the best relationship with Potential Gradient, but particle count alone showed a weaker, but similar relationship. The increase in particle count caused by annual bonfire and fireworks celebrations (November) was evidenced in both Potential Gradient and particle numbers. Daily regression or correlation did not show a consistent relationship. In the larger Bristol data set, increasing humidity led to a reduction of Potential Gradient, while increasing particle number led to an increase.
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urban and rural measurements of atmospheric Potential Gradient
Journal of Electrostatics, 2019Co-Authors: James C Matthews, Matthew D Wright, Dominic J Clarke, Erica L Morley, Hugo G Silva, A J Bennett, Daniel Robert, Dudley E ShallcrossAbstract:Abstract Atmospheric Potential Gradient was measured at three sites within the Bristol area of the UK between 19th May and 24th June 2016. Two sites were on rooftops within the city of Bristol, 800 m apart from each other, while the third was in a rural location 17 km to the south. Potential Gradient measurements at the two rooftop urban sites showed great temporal similarity, implying that a rooftop measurement may be assumed to represent the local urban area. Frequency domain analysis indicated a half-day cycle in the urban sites that was not observed in the rural site, consistent with other studies showing the effect of traffic aerosol on Potential Gradient measurements. The correlation between the two urban sites was not affected by an increase in aerosol concentration. Removal of data during rainfall, as well as one hour before and after rain, removed some of the larger changes in Potential Gradient typical of disturbed weather. However, large changes of Potential Gradient still existed, showing that rainfall alone should not be relied upon as an indicator of a non-fair weather Potential Gradient.
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Diurnal variations of atmospheric Potential Gradient disruption near to high voltage power lines
Journal of Atmospheric and Solar-Terrestrial Physics, 2012Co-Authors: James C MatthewsAbstract:Abstract The Earth's background Potential Gradient (PG) has a diurnal cycle (the ‘Carnegie curve’) that can be exhibited in fair weather when there are no local sources of space charge. High voltage power lines can create corona ions which are released into the atmosphere and can disrupt the natural PG. A fixed site monitoring station measured the vertical Potential Gradient at 1 s intervals alongside local weather conditions to investigate the time of day at which corona production is greatest downwind of a power line. In upwind conditions, the average PG curve returned correlates well with the Carnegie curve, but this is masked under downwind conditions. Overnight, the PG downwind of the monitoring station is more variable and more negative than upwind. Downwind of the power line there is significantly more variability of Potential Gradient after sunrise and before sunset on most days.
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Corona ion induced atmospheric Potential Gradient perturbations near high voltage power lines
Atmospheric Environment, 2010Co-Authors: James C Matthews, Jonathan P. Ward, Pa Keitch, Denis L. HenshawAbstract:High voltage power lines are known to produce corona ions that can be carried from the line by the wind, progressively attaching to ambient aerosol particles and causing fluctuations in the Earth’s atmospheric Potential Gradient. A fixed site monitoring station was installed near two power lines, which recorded the Potential Gradient at 1 s intervals and the ambient weather conditions every 10 min. The station ran continuously from January 2007 to December 2008, accumulating long-term data. Results from 2008 show an increase in Potential Gradient variability when a wind is blowing across the power lines towards the station, indicating that corona ions may be present in this environment.
Lei Ke - One of the best experts on this subject based on the ideXlab platform.
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Fabrication of ZnO-based thick film varistors with high Potential Gradient
Rare Metals, 2010Co-Authors: Lei Ke, Dongmei Jiang, Xueming MaAbstract:ZnO-based thick film varistors have been fabricated by Y2O3 doping and low-temperature sintering, of which the sample with the best electrical properties has a high Potential Gradient value of 3159.4 V/mm. The effects of Y2O3 doping concentration and sintering temperature on the Potential Gradient of the samples were systematically investigated. The results show that the sample with the best electrical properties can be obtained by doping 0.08 mol% Y2O3 and sintering at 725°C. Under these optimum preparation conditions, the leakage current and the nonlinear coefficient are found to be 36.4 μA and 13.1. The sample with the best electrical properties has a grain size of 1.290 μm, a single grain boundary voltage of 4.08 V, a barrier height of 0.81 eV, and a depletion layer width of 10.2 nm, which are determined by thermionic emission. Small grain size with good grain boundary characteristics is beneficial to improve the electrical properties of varistors and promote the Potential Gradient.
-
HIGH Potential Gradient OF ZnO VARISTORS PREPARED BY Y2O3-DOPING AND LOW-TEMPERATURE SINTERING
Modern Physics Letters B, 2009Co-Authors: Lei Ke, Dongmei Jiang, Chun-xia Wang, Xueming MaAbstract:A high Potential Gradient of ZnO varistors were fabricated by Y2O3-doping and low-temperature sintering. The value of the Potential Gradient increased to 2460.5 V/mm with the Y2O3 content of 0.08 mol% and the sintering temperature of 800°C. The effects of Y2O3-doping and sintering temperature on the electrical properties of ZnO varistors were investigated. Under the given experimental conditions, additive Y2O3 exists in the form of Y2O3 phase after sintering at 800°C. High-energy ball-milling in the early period of the experiment induced the grain refinement and realized the sintering formation at the lower temperature of 800°C. Both Y2O3-doping and low-temperature sintering restrained the ZnO grain growth and increased the Potential Gradient.
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HIGH Potential Gradient OF Y2O3-DOPED THICK FILM VARISTORS
Surface Review and Letters, 2009Co-Authors: Lei Ke, Dongmei Jiang, Xueming MaAbstract:The electrical and microstructural properties of a series of ZnO-based thick film varistors (TFVs) doped with 0.00, 0.02, 0.04, 0.06, 0.08, and 0.10 mol% Y2O3 were studied. It was found that sample doped with 0.08 mol% Y2O3 showed the highest Potential Gradient of 3159.4 V/mm with a leakage current of 36.4 μA and a nonlinear exponent of 13.1. The ZnO grain size decreased with increasing Y2O3 content, which was the origin for the increase in Potential Gradient. Raman spectra results showed that the tensile stress increased linearly with Y2O3 doping. Larger tensile stress was considered to result from the lattice distortion and inevitably influenced the grain boundary characteristics. While the Y2O3 doping concentration was beyond 0.08 mol%, the effect of residual stress on electrical properties was much more remarkable than that of grain size, leading Potential Gradient to be weakened. As a result, high Potential Gradient of ZnO-based TFVs could be obtained with Y2O3 doping concentration of 0.08 mol% and qualified as excellent candidates for high voltage varistor application.
Dongmei Jiang - One of the best experts on this subject based on the ideXlab platform.
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Fabrication of ZnO-based thick film varistors with high Potential Gradient
Rare Metals, 2010Co-Authors: Lei Ke, Dongmei Jiang, Xueming MaAbstract:ZnO-based thick film varistors have been fabricated by Y2O3 doping and low-temperature sintering, of which the sample with the best electrical properties has a high Potential Gradient value of 3159.4 V/mm. The effects of Y2O3 doping concentration and sintering temperature on the Potential Gradient of the samples were systematically investigated. The results show that the sample with the best electrical properties can be obtained by doping 0.08 mol% Y2O3 and sintering at 725°C. Under these optimum preparation conditions, the leakage current and the nonlinear coefficient are found to be 36.4 μA and 13.1. The sample with the best electrical properties has a grain size of 1.290 μm, a single grain boundary voltage of 4.08 V, a barrier height of 0.81 eV, and a depletion layer width of 10.2 nm, which are determined by thermionic emission. Small grain size with good grain boundary characteristics is beneficial to improve the electrical properties of varistors and promote the Potential Gradient.
-
HIGH Potential Gradient OF ZnO VARISTORS PREPARED BY Y2O3-DOPING AND LOW-TEMPERATURE SINTERING
Modern Physics Letters B, 2009Co-Authors: Lei Ke, Dongmei Jiang, Chun-xia Wang, Xueming MaAbstract:A high Potential Gradient of ZnO varistors were fabricated by Y2O3-doping and low-temperature sintering. The value of the Potential Gradient increased to 2460.5 V/mm with the Y2O3 content of 0.08 mol% and the sintering temperature of 800°C. The effects of Y2O3-doping and sintering temperature on the electrical properties of ZnO varistors were investigated. Under the given experimental conditions, additive Y2O3 exists in the form of Y2O3 phase after sintering at 800°C. High-energy ball-milling in the early period of the experiment induced the grain refinement and realized the sintering formation at the lower temperature of 800°C. Both Y2O3-doping and low-temperature sintering restrained the ZnO grain growth and increased the Potential Gradient.
-
HIGH Potential Gradient OF Y2O3-DOPED THICK FILM VARISTORS
Surface Review and Letters, 2009Co-Authors: Lei Ke, Dongmei Jiang, Xueming MaAbstract:The electrical and microstructural properties of a series of ZnO-based thick film varistors (TFVs) doped with 0.00, 0.02, 0.04, 0.06, 0.08, and 0.10 mol% Y2O3 were studied. It was found that sample doped with 0.08 mol% Y2O3 showed the highest Potential Gradient of 3159.4 V/mm with a leakage current of 36.4 μA and a nonlinear exponent of 13.1. The ZnO grain size decreased with increasing Y2O3 content, which was the origin for the increase in Potential Gradient. Raman spectra results showed that the tensile stress increased linearly with Y2O3 doping. Larger tensile stress was considered to result from the lattice distortion and inevitably influenced the grain boundary characteristics. While the Y2O3 doping concentration was beyond 0.08 mol%, the effect of residual stress on electrical properties was much more remarkable than that of grain size, leading Potential Gradient to be weakened. As a result, high Potential Gradient of ZnO-based TFVs could be obtained with Y2O3 doping concentration of 0.08 mol% and qualified as excellent candidates for high voltage varistor application.
Dudley E Shallcross - One of the best experts on this subject based on the ideXlab platform.
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the relationship between aerosol concentration and atmospheric Potential Gradient in urban environments
Science of The Total Environment, 2020Co-Authors: Matthew D Wright, James C Matthews, Hugo G Silva, Asan Bacak, Carl J Percival, Dudley E ShallcrossAbstract:Abstract Urban aerosol is a growing concern for people living within cities; aerosol have been implicated in many ill health conditions, including that of the lung and of the heart. Atmospheric Potential Gradient is a consequence of charge carried to the ionosphere through thunderstorms, and its value depends on highly electrically mobile ion concentrations, hence local conductivity of the air. Ions attach to aerosol in the atmosphere, reducing their mobility and therefore increasing the Potential Gradient, and so Potential Gradient measurements have been suggested as a proxy for aerosol measurements. Particle number count, size distribution and Potential Gradient were measured for two campaigns in Manchester, U.K., and one campaign in Bristol, U.K. Using a factor based on size distribution to account for preferential attachment at larger sizes provided the best relationship with Potential Gradient, but particle count alone showed a weaker, but similar relationship. The increase in particle count caused by annual bonfire and fireworks celebrations (November) was evidenced in both Potential Gradient and particle numbers. Daily regression or correlation did not show a consistent relationship. In the larger Bristol data set, increasing humidity led to a reduction of Potential Gradient, while increasing particle number led to an increase.
-
urban and rural measurements of atmospheric Potential Gradient
Journal of Electrostatics, 2019Co-Authors: James C Matthews, Matthew D Wright, Dominic J Clarke, Erica L Morley, Hugo G Silva, A J Bennett, Daniel Robert, Dudley E ShallcrossAbstract:Abstract Atmospheric Potential Gradient was measured at three sites within the Bristol area of the UK between 19th May and 24th June 2016. Two sites were on rooftops within the city of Bristol, 800 m apart from each other, while the third was in a rural location 17 km to the south. Potential Gradient measurements at the two rooftop urban sites showed great temporal similarity, implying that a rooftop measurement may be assumed to represent the local urban area. Frequency domain analysis indicated a half-day cycle in the urban sites that was not observed in the rural site, consistent with other studies showing the effect of traffic aerosol on Potential Gradient measurements. The correlation between the two urban sites was not affected by an increase in aerosol concentration. Removal of data during rainfall, as well as one hour before and after rain, removed some of the larger changes in Potential Gradient typical of disturbed weather. However, large changes of Potential Gradient still existed, showing that rainfall alone should not be relied upon as an indicator of a non-fair weather Potential Gradient.