Contributions to develop a ZnO based surge protector

摘要

ZnO based surge protective devices have been made and characterized both morphological (SEM microscopy and interferometry) and electrical (U/I characteristic and dielectric spectroscopy). SEM microscopy analyzes revealed that the disks of metal oxides sintered at 12000C present a homogeneous distribution of ZnO grains, without pores and well-defined intergranular limits. It was also found that Ag electrodes (applied by Ag paste to 650°C) are well anchored in the structure of the sintered material. The interferometry measurements revealed that the sintered material surface roughness ranges within ± 3μm. The electrical measurements revealed that the threshold voltage of the achieved devices is proportional to the thickness of the disks of approximately 156V / mm. Reverse currents, measured at 0.8 of the threshold voltage were between 0.28 and 0.31mA. Also, the measurements of dielectric spectroscopy revealed that the dielectric loss is highly dependent on frequency, respectively about 0.15 at 40 Hz and decreases exponentially to 0.019 at 10 kHz.