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http://dx.doi.org/10.4191/KCERS.2002.39.3.286

Effect of Firing Temperature on Microstructure and the Electrical Properties of a ZnO-based Multilayered Chip Type Varistor(MLV)  

Kim, Chul-Hong (Department of Inorganic Materials Engineering, Kyungpook National University)
Kim, Jin-Ho (Department of Inorganic Materials Engineering, Kyungpook National University)
Publication Information
Journal of the Korean Ceramic Society / v.39, no.3, 2002 , pp. 286-293 More about this Journal
Abstract
Microstructure and the electrical porperties of a ZnO-based multilayered chip-type varistor(abbreviated as MLV) with Ag/Pd(7:3) inner electrode have been studied as a function of firing of temperature. At 1100$^{\circ}$C, inner electrode layers began to show nonuniform thickness and small voids, which resulted in significant disappearance of the electrode pattern and delamination at 1100$^{\circ}$C. MLVs fired at 950$^{\circ}$C showed large degradation in leakage current, probably due to incomplete redistribution of liquid and transition metal elements in pyrochlore phase decomposition. Those fired at 1100$^{\circ}$C and above, on the other hand, revealed poor varistor characteristics and their reproductibility, which are though to stem from the deformation of inner electrode pattern, the reaction between electrode materials and ZnO-based ceramics, and the volatilization of $Bi_2O_3$. Throughout the firing temperature range of 950∼1100$^{\circ}$C, capacitance and leakage current increased while breakdown voltage and peak current decreased with the increase of firing temperature, but nonlinear coefficient and clamping ratio kept almost constant at ∼30 and 1.4, respectively. In particular, those fired between 1000$^{\circ}$C and 1050$^{\circ}$C showed stable varistor characteristics with high reproducibility. It seems that Ag/Pd(7:3) alloy is one of the electrode materials applicable to most ZnO-based MLVs incorporating with $Bi_2O_3$ when cofired up to 1050$^{\circ}$C.
Keywords
Multilayered Chip Varistor(MLV); ESD; Firing temperature; Varistor characteristics;
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Times Cited By KSCI : 1  (Citation Analysis)
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