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Inhomogeneous Conductivity in Varistor Ceramics: Methods of Investigation
Author(s) -
Hohenberger Gert,
Tomandl Gerhard,
Ebert Rolf,
Taube Thomas
Publication year - 1991
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1991.tb08260.x
Subject(s) - varistor , materials science , grain boundary , ceramic , microstructure , current (fluid) , conductivity , breakdown voltage , flux (metallurgy) , voltage , composite material , mineralogy , electrical engineering , metallurgy , chemistry , engineering
The grain boundaries in zinc oxide ceramics exhibit different electrical behaviors. This results in separate paths of current flux through the microstructure and also in different breakdown voltages of each path. The paper describes some new methods for characterization of these paths. A galvanic determination is able to show the number of paths and their distribution across the varistor surface. The differences in breakdown voltage are visible using a line scan method. Current images in SEM can detect the paths of current along a varistor surface. Possible reasons for inhomogeneous current flux are inhomogeneous distribution of dopants, insufficient binder burnout, and pressing faults.