ZnO-Bi2O3-based varistor ceramics doped with Yb2O3 in the range from 0 to 0.4% （molar fraction） were obtained by a solid reaction route. The X-ray diffractometry （XRD） and scanning electron microscopy （SEM） were...ZnO-Bi2O3-based varistor ceramics doped with Yb2O3 in the range from 0 to 0.4% （molar fraction） were obtained by a solid reaction route. The X-ray diffractometry （XRD） and scanning electron microscopy （SEM） were applied to characterize the phases and microstructure of the varistor ceramics, and a DC parameter instrument for varistor ceramics was applied to investigate their electrical properties and V-I characteristics. The XRD analysis of the samples shows that the ZnO phase, Bi2O3 phase, ZnTSbaOl2-type spinel phase and Zn2Bi3Sb3O14-type pyrochlore are present, and the Yb2O3 phases and Sb2O4 phases are found in varistor ceramics with increasing amounts of Yb2O3. The average size of ZnO grain firstly increases and then decreases with the increase of Yb2O3 content. The result also shows that the threshold voltage is between 656 V/nun and 1 232 V/mm, the nonlinear coefficient is in the range of 14.1-22.3, and the leakage current is between 0.60 μA and 19.6 μA. The 0.20% Yb2O3-added ZnO-Bi2O3-based varistor ceramics sintered at 900 ℃ have the best electrical characteristics.展开更多
The effect of different molar ratios of Y2O3 and Y（NO3）3 on the microstructure and electrical response of ZnO-Bi203-based varistor ceramics sintered at 1 000 ℃ was investigated, and the mechanism by which this dopi...The effect of different molar ratios of Y2O3 and Y（NO3）3 on the microstructure and electrical response of ZnO-Bi203-based varistor ceramics sintered at 1 000 ℃ was investigated, and the mechanism by which this doping improves the electrical characteristics of ZnO-Bi203-based varistor ceramics was discussed. With increasing amounts of Y（NO3）3 or Y2O3 in the starting composition, Y2O3, Sb204 and Y-containing Bi-rich phase form, and the average grain size significantly decreases. The average grain size significantly decreases as the contents of rare earth compounds of Y（NO3）3 or Y2O3 increase. The maximum value of the nonlinear coefficient is found at 0.16% Y（NO3）3 or 0.02% YaO3 （molar fraction） doped varistor ceramics, and there is an increase of 122% or 35% compared with the varistor ceramics without Y（NO3）3 or Y2O3. The threshold voltage VT of Y（NO3）3 and Y2O3 reaches at 1 460 V/mm and 1 035 V/ram, respectively. The results also show that varistor sample doped with Y（NO3）3 has a remarkably more homogeneous and denser microstructure in comparison to the sample doped with Y2O3.展开更多
The influence of soaking time on the nonlinear electrical behavior and dielectric properties of TiO2-based varistor ceramics was investigated. Based on single sintering process, six disk samples of （Sr, Bi, Si, Ta）-...The influence of soaking time on the nonlinear electrical behavior and dielectric properties of TiO2-based varistor ceramics was investigated. Based on single sintering process, six disk samples of （Sr, Bi, Si, Ta）-doped TiO2-based varistor ceramics were fabricated by sintering at 1 250 ℃ for 0.5-5.0 h. The samples were characterized by X-ray diffraction, voltage-current characteristics, energy spectra, metallographs, breakdown voltages, and apparent dielectric constant. It is found that the breakdown electrical field intensity at a current density of 10 mA/cma decreases from 5.5 to 4.1 V/mm first and then increases to 7.0 V/mm, the nonlinear coefficient increases from 2.39 to 2.62 first and then decreases to 2.42, and the apparent dielectric constant increases from 98 200 to 1l5 049 first and then decreases to 73 865 with the soaking time increasing from 0.5 to 5.0 h. These indicate that the optimal soaking time is 2.0-3.0 h considering both nonlinear electrical behavior and dielectric properties.展开更多
ZnO varistors are prepared using the 0.1-0.3mm ZnO powders. The effects of the sintering temperature, contents of In2O3 doping on the non-linear properties of ZnO varistors have been investigated. Theresults show that...ZnO varistors are prepared using the 0.1-0.3mm ZnO powders. The effects of the sintering temperature, contents of In2O3 doping on the non-linear properties of ZnO varistors have been investigated. Theresults show that this kind of ZnO powder has a high sintering activity. It is suitable for making the low voltage varistors. The Vc decreases with the increase of sintered temperature, when the In2O3 content is fixed(0. 98 %, mass fraction), and increases with the increase of In2O3 contents when the temperature is steady.展开更多
The microstructure and electrical properties of ZnO-Bi2O3-Yb2O3 based varistor ceramics were investigated with various temperature effects from 900°C to 1050°C.From the results,it was observed that the incre...The microstructure and electrical properties of ZnO-Bi2O3-Yb2O3 based varistor ceramics were investigated with various temperature effects from 900°C to 1050°C.From the results,it was observed that the increase of sintering temperature offers a reduced capacitive effect from 0.460 nF to 0.321 nF.Furthermore,the grain sizes of varistors were varied from 6.8μm to 9.8μm.The consequence of such smaller grain sizes provided a better voltage gradient of about 895 V/mm for the disc sintered at 900°C and fallen drastically to 410 V/mm for the sample sintered at 1050°C.In addition,there was an increase of non-linearity index to a maximum value of 36.0 and reduced leakage current of 0.026 mA/cm2.However,the density of the varistor decreased with an increase of temperature from 5.41 g/cm3 to 5.24 g/cm3.With this base,the influence of varistor capacitance and high voltage gradient were scrutinized and it led an improved transition speed of the varistor assembly from non-conduction to conduction mode during intruding nanosecond transients.展开更多
Microstructure and electrical properties of La2 O3-doped ZnO-Bi2 O3 thin films prepared by sol–gel process have been investigated.X-ray diffraction shows that most diffraction peaks of ZnO are equal,and the crystals ...Microstructure and electrical properties of La2 O3-doped ZnO-Bi2 O3 thin films prepared by sol–gel process have been investigated.X-ray diffraction shows that most diffraction peaks of ZnO are equal,and the crystals of ZnO grow well.Scanning electron microscopy and atomic force microscopy results indicate that the samples have a good structure and lower surface roughness.The nonlinear V–I characteristics of the films show that La2 O3 develops the electrical properties largely and the best doped content is 0.3% lanthanum ion,with the leakage current of 0.25 mA,the threshold field of 150 V/mm and the nonlinear coefficient of 4.0 in detail.展开更多
ZnO-Bi2O3-based varistor ceramics doped with EU2O3 in a range from 0 to 0.4% were obtained by high-energy ball milling and fired at 900-1000 ℃ for 2 h. XRD and SEM were applied to determine the phases and microstruct...ZnO-Bi2O3-based varistor ceramics doped with EU2O3 in a range from 0 to 0.4% were obtained by high-energy ball milling and fired at 900-1000 ℃ for 2 h. XRD and SEM were applied to determine the phases and microstructure of the varistor ceramics. A DC parameter instrument was applied to investigate the electronic properties and V-I characteristics. The XRD analysis of Eu2O3-doped ZnO-Bi2O3-based varistor ceramics shows that the ZnO, Eu-containing Bi-rich, Zn7Sb2O12-type spinel and Zn2Bi3Sb3O14-type which is the pyrochlore phase are present. With increasing Eu2O3 content, the average size of ZnO grain firstly decreases and then increases. The grain boundary defect model was particularly used to explain the excellent nonlinearity of ZnO-Bi2O3-based varistor ceramics with the addition of0.1% Eu2O3 and sintered at 950 ℃.展开更多
The degradation phenomena due to the energy pulse in the high-energy ZnO varistors used for deexitation and overvoltage protection of hydroelectric generator are investigated. The energy pulse, obtained by releasing t...The degradation phenomena due to the energy pulse in the high-energy ZnO varistors used for deexitation and overvoltage protection of hydroelectric generator are investigated. The energy pulse, obtained by releasing the energy stored in an inductor, can be equivalent to the combination of the DC field components and the energy component. The variations of the characterized voltages, nonlinear coefficients and pre-breakdown V-A characteristics, increase with the number of the applied energy pulse. The asymmetrical variations of the electric properties of the high-energy ZnO varistors after the energy pulse arise from the deformation of the double Schottky barriers due to the ion migration occuring in the depletion layer and in the grain boundary.展开更多
基金Project(BK2011243) supported by the Natural Science Foundation of Jiangsu Province,ChinaProject(2007DA10512711408) supported by the Visiting Scholarship of State Key Laboratory of Power Transmission Equipment & System Security and New Technology (Chongqing University),China+4 种基金Project(EIPE11204) supported by the State Key Laboratory of Electrical Insulation and Power Equipment,ChinaProject(KF201104) supported by the State Key Laboratory of New Ceramic and Fine Processing,ChinaProject(KFJJ201105) supported by the Opening Project of State Key Laboratory of Electronic Thin Films and Integrated Devices,ChinaProject(10KJD430002) supported by the Universities Natural Science Research Project of Jiangsu Province,ChinaProject(11JDG084) supported by the Research Foundation of Jiangsu University,China
文摘ZnO-Bi2O3-based varistor ceramics doped with Yb2O3 in the range from 0 to 0.4% （molar fraction） were obtained by a solid reaction route. The X-ray diffractometry （XRD） and scanning electron microscopy （SEM） were applied to characterize the phases and microstructure of the varistor ceramics, and a DC parameter instrument for varistor ceramics was applied to investigate their electrical properties and V-I characteristics. The XRD analysis of the samples shows that the ZnO phase, Bi2O3 phase, ZnTSbaOl2-type spinel phase and Zn2Bi3Sb3O14-type pyrochlore are present, and the Yb2O3 phases and Sb2O4 phases are found in varistor ceramics with increasing amounts of Yb2O3. The average size of ZnO grain firstly increases and then decreases with the increase of Yb2O3 content. The result also shows that the threshold voltage is between 656 V/nun and 1 232 V/mm, the nonlinear coefficient is in the range of 14.1-22.3, and the leakage current is between 0.60 μA and 19.6 μA. The 0.20% Yb2O3-added ZnO-Bi2O3-based varistor ceramics sintered at 900 ℃ have the best electrical characteristics.
基金Project(BK2011243) supported by the Natural Science Foundation of Jiangsu Province, ChinaProject(EIPE11204) supported by the State Key Laboratory of Electrical Insulation and Power Equipment, China+4 种基金Project(KF201104) supported by the State Key Laboratory of New Ceramic and Fine Processing, ChinaProject(KFJJ201105) supported by the Opening Program of State key Laboratory of Electronic Thin Films and Integrated Devices, ChinaProject(2011-22) supported by the State Key Laboratory of Inorganic Synthesis and Preparative Chemistry of Jilin University, ChinaProject(10KJD430002) supported by the Universities Natural Science Research Project of Jiangsu Province, ChinaProject(11JDG084) supported by the Research Foundation of Jiangsu University, China
文摘The effect of different molar ratios of Y2O3 and Y（NO3）3 on the microstructure and electrical response of ZnO-Bi203-based varistor ceramics sintered at 1 000 ℃ was investigated, and the mechanism by which this doping improves the electrical characteristics of ZnO-Bi203-based varistor ceramics was discussed. With increasing amounts of Y（NO3）3 or Y2O3 in the starting composition, Y2O3, Sb204 and Y-containing Bi-rich phase form, and the average grain size significantly decreases. The average grain size significantly decreases as the contents of rare earth compounds of Y（NO3）3 or Y2O3 increase. The maximum value of the nonlinear coefficient is found at 0.16% Y（NO3）3 or 0.02% YaO3 （molar fraction） doped varistor ceramics, and there is an increase of 122% or 35% compared with the varistor ceramics without Y（NO3）3 or Y2O3. The threshold voltage VT of Y（NO3）3 and Y2O3 reaches at 1 460 V/mm and 1 035 V/ram, respectively. The results also show that varistor sample doped with Y（NO3）3 has a remarkably more homogeneous and denser microstructure in comparison to the sample doped with Y2O3.
基金Project(50872001) supported by the National Natural Science Foundation of ChinaProjects(KJ2007B132, KJ2009A006Z) supported by the Scientific Research Foundation of Education Department of Anhui Province, ChinaProject(XJ200907) supported by the Foundation of Construction of Quality Project of Anhui University, China
文摘The influence of soaking time on the nonlinear electrical behavior and dielectric properties of TiO2-based varistor ceramics was investigated. Based on single sintering process, six disk samples of （Sr, Bi, Si, Ta）-doped TiO2-based varistor ceramics were fabricated by sintering at 1 250 ℃ for 0.5-5.0 h. The samples were characterized by X-ray diffraction, voltage-current characteristics, energy spectra, metallographs, breakdown voltages, and apparent dielectric constant. It is found that the breakdown electrical field intensity at a current density of 10 mA/cma decreases from 5.5 to 4.1 V/mm first and then increases to 7.0 V/mm, the nonlinear coefficient increases from 2.39 to 2.62 first and then decreases to 2.42, and the apparent dielectric constant increases from 98 200 to 1l5 049 first and then decreases to 73 865 with the soaking time increasing from 0.5 to 5.0 h. These indicate that the optimal soaking time is 2.0-3.0 h considering both nonlinear electrical behavior and dielectric properties.
文摘ZnO varistors are prepared using the 0.1-0.3mm ZnO powders. The effects of the sintering temperature, contents of In2O3 doping on the non-linear properties of ZnO varistors have been investigated. Theresults show that this kind of ZnO powder has a high sintering activity. It is suitable for making the low voltage varistors. The Vc decreases with the increase of sintered temperature, when the In2O3 content is fixed(0. 98 %, mass fraction), and increases with the increase of In2O3 contents when the temperature is steady.
文摘The microstructure and electrical properties of ZnO-Bi2O3-Yb2O3 based varistor ceramics were investigated with various temperature effects from 900°C to 1050°C.From the results,it was observed that the increase of sintering temperature offers a reduced capacitive effect from 0.460 nF to 0.321 nF.Furthermore,the grain sizes of varistors were varied from 6.8μm to 9.8μm.The consequence of such smaller grain sizes provided a better voltage gradient of about 895 V/mm for the disc sintered at 900°C and fallen drastically to 410 V/mm for the sample sintered at 1050°C.In addition,there was an increase of non-linearity index to a maximum value of 36.0 and reduced leakage current of 0.026 mA/cm2.However,the density of the varistor decreased with an increase of temperature from 5.41 g/cm3 to 5.24 g/cm3.With this base,the influence of varistor capacitance and high voltage gradient were scrutinized and it led an improved transition speed of the varistor assembly from non-conduction to conduction mode during intruding nanosecond transients.
基金Project(20123227120021)supported by the Specialized Research Fund for the Doctoral Program of Higher Education of ChinaProject(BK2012156)supported by the Natural Science Foundation of Jiangsu Province,China+3 种基金Project(KFJJ201105)supported by the Opening Project of State Key Laboratory of Electronic Thin Films and Integrated Devices,ChinaProject(CJ20125001)supported by the Application Program for Basic Research of Changzhou,ChinaProject(13KJB430006)supported by the Universities Natural Science Research project of Jiangsu Province,ChinaProject supported by the Industrial Center of Jiangsu University Undergraduate Practice-Innovation Training Program,China
文摘Microstructure and electrical properties of La2 O3-doped ZnO-Bi2 O3 thin films prepared by sol–gel process have been investigated.X-ray diffraction shows that most diffraction peaks of ZnO are equal,and the crystals of ZnO grow well.Scanning electron microscopy and atomic force microscopy results indicate that the samples have a good structure and lower surface roughness.The nonlinear V–I characteristics of the films show that La2 O3 develops the electrical properties largely and the best doped content is 0.3% lanthanum ion,with the leakage current of 0.25 mA,the threshold field of 150 V/mm and the nonlinear coefficient of 4.0 in detail.
基金Projects(BK2011243,BK2012156) supported by the Natural Science Foundation of Jiangsu Province,ChinaProject(20123227120021) supported by the Specialized Research Fund for the Doctoral Program of Higher Education,China+3 种基金Project(KFJJ201105) supported by the Opening Project of State key Laboratory of Electronic Thin Films and Integrated Devices,ChinaProject(10KJD430002) supported by the Universities Natural Science Research Project of Jiangsu Province,ChinaProject(13KJB430006) supported by the Application Program for Basic Research of Changzhou,ChinaProject supported by the Industrial Center of Jiangsu University Undergraduate Practice-Innovation Training Project,China
文摘ZnO-Bi2O3-based varistor ceramics doped with EU2O3 in a range from 0 to 0.4% were obtained by high-energy ball milling and fired at 900-1000 ℃ for 2 h. XRD and SEM were applied to determine the phases and microstructure of the varistor ceramics. A DC parameter instrument was applied to investigate the electronic properties and V-I characteristics. The XRD analysis of Eu2O3-doped ZnO-Bi2O3-based varistor ceramics shows that the ZnO, Eu-containing Bi-rich, Zn7Sb2O12-type spinel and Zn2Bi3Sb3O14-type which is the pyrochlore phase are present. With increasing Eu2O3 content, the average size of ZnO grain firstly decreases and then increases. The grain boundary defect model was particularly used to explain the excellent nonlinearity of ZnO-Bi2O3-based varistor ceramics with the addition of0.1% Eu2O3 and sintered at 950 ℃.
文摘The degradation phenomena due to the energy pulse in the high-energy ZnO varistors used for deexitation and overvoltage protection of hydroelectric generator are investigated. The energy pulse, obtained by releasing the energy stored in an inductor, can be equivalent to the combination of the DC field components and the energy component. The variations of the characterized voltages, nonlinear coefficients and pre-breakdown V-A characteristics, increase with the number of the applied energy pulse. The asymmetrical variations of the electric properties of the high-energy ZnO varistors after the energy pulse arise from the deformation of the double Schottky barriers due to the ion migration occuring in the depletion layer and in the grain boundary.
