The paper reports on the influence of processing on microstructure and electrical properties of multilayer varistors based on zinc oxide doped with Bi2O3,Sb2O3,Co2O3,MnO,Cr2O3,B2O3,and SiO2.0.5–1 wt%of AlF3–CaB4O7 w...The paper reports on the influence of processing on microstructure and electrical properties of multilayer varistors based on zinc oxide doped with Bi2O3,Sb2O3,Co2O3,MnO,Cr2O3,B2O3,and SiO2.0.5–1 wt%of AlF3–CaB4O7 was used as a new effective sintering aid.The behavior of green laminates during heating was characterized using differential thermal analysis and a heating microscope.As revealed by XRD,SEM,and EDS methods,the varistor layers are composed of ZnO grains of 1–5μm size,submicrometer spinel and pyrochlore grains situated at the ZnO grain boundaries,and nanometric Bi2O3-rich films surrounding ZnO grains.Complex impedance studies carried out in the frequency range of 0.01 Hz–2 MHz at temperatures changing from –30 to 150℃ imply the formation of semiconducting grains and insulating grain boundaries.Frequency dependence of dielectric permittivity shows a high plateau at lower frequencies,typical for barrier layer capacitance effect.The fabricated multilayer varistors show nonlinear current–voltage characteristics with a high nonlinear coefficient of 26–38.The breakdown voltage was found to decrease within the range of 66–130 V with sintering temperature increasing from 1000 to 1100℃.Good surge current capability of the varistors was confirmed by the tests using 8/20μs pulses.展开更多
基金supported by the National Science Centre, Poland, under the Grant No. 2015/17/D/ST7/04141
文摘The paper reports on the influence of processing on microstructure and electrical properties of multilayer varistors based on zinc oxide doped with Bi2O3,Sb2O3,Co2O3,MnO,Cr2O3,B2O3,and SiO2.0.5–1 wt%of AlF3–CaB4O7 was used as a new effective sintering aid.The behavior of green laminates during heating was characterized using differential thermal analysis and a heating microscope.As revealed by XRD,SEM,and EDS methods,the varistor layers are composed of ZnO grains of 1–5μm size,submicrometer spinel and pyrochlore grains situated at the ZnO grain boundaries,and nanometric Bi2O3-rich films surrounding ZnO grains.Complex impedance studies carried out in the frequency range of 0.01 Hz–2 MHz at temperatures changing from –30 to 150℃ imply the formation of semiconducting grains and insulating grain boundaries.Frequency dependence of dielectric permittivity shows a high plateau at lower frequencies,typical for barrier layer capacitance effect.The fabricated multilayer varistors show nonlinear current–voltage characteristics with a high nonlinear coefficient of 26–38.The breakdown voltage was found to decrease within the range of 66–130 V with sintering temperature increasing from 1000 to 1100℃.Good surge current capability of the varistors was confirmed by the tests using 8/20μs pulses.
