Title :
Capacitance changes in degraded metal oxide varistors
Author :
Jaroszewski, M. ; Wieczorek, K. ; Bretuj, W. ; Kostyla, Pawel
Author_Institution :
Inst. of Electr. Eng. Fundamentals, Wroclaw Univ. of Technol., Poland
Abstract :
ZnO based ceramics show a highly nonlinear current-voltage (I-V) characteristic due to intergranular layers at the boundaries of ZnO grains. This research indicates that the junctions formed on the border between ZnO grains and the intergranular phase are responsible for the creation of potential barriers which control the flow of current through the bulk of such a ceramic. Having polycrystalline nature and a large number of intergranular barriers, and so a high energy absorption capability, ZnO ceramics are used as active components in overvoltage protection devices. However, as a result of charge transport the height of the barriers decreases and varistor degradation occurs. The degradation seems to affect mainly the prebreakdown region of the I-V curve and it results in increased leakage current. This paper presents a part of research aimed at assessing the effect of ageing on the capacitance characteristic of ZnO varistors.
Keywords :
II-VI semiconductors; ageing; capacitance; ceramics; grain boundaries; leakage currents; overvoltage protection; semiconductor device breakdown; varistors; zinc compounds; ZnO; ZnO grain boundaries; ZnO varistors; ageing; capacitance; charge transport; current flow control; electric prebreakdown; high energy ZnO based ceramics; intergranular potential barrier layers; leakage current; metal oxide varistor degradation; nonlinear I-V curves; nonlinear current-voltage curves; overvoltage protection devices; Absorption; Aging; Capacitance; Ceramics; Degradation; Leakage current; Protection; Varistors; Voltage control; Zinc oxide;
Conference_Titel :
Solid Dielectrics, 2004. ICSD 2004. Proceedings of the 2004 IEEE International Conference on
Print_ISBN :
0-7803-8348-6
DOI :
10.1109/ICSD.2004.1350537