| 소성온도에 따른 ZnO계 적층형 칩 바리스터의 미세구조와 전기적 특성의 변화 |
| 김철홍, 김진호 |
| 경북대학교 무기재료공학과 |
| Effect of Firing Temperature on Microstructure and the Electrical Properties of a ZnO-based Multilayered Chip Type Varistor(MLV) |
| Chul-Hong Kim, Jin-Ho Kim |
| Department of Inorganic Materials Engineering, Kyungpook National University |
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| ABSTRACT |
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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. |
| Key words:
Multilayered Chip Varistor(MLV), ESD, Firing temperature, Varistor characteristics |
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