PROCESSING AND CHARACTERIZATION OF LOW-VOLTAGE VARISTORS
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Data
1994-05-01
Autores
Cerri, J. A.
Steil, M. C.
Longo, Elson [UNESP]
Varela, José Arana [UNESP]
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Editor
Belgian Ceramic Society
Resumo
ZnO seed particles and Cr2O3 were used in this study to control the microstructure of ZnO varistors. The seed particles were prepared by adding 1.0 mol % BaO to ZnO. The powder was then calcined at 800-degrees-C for 2 h, pressed into pellets and sintered at 1400-degrees-C for 8 h. The sintered ZnO was ground and the BaO eliminated by washing in water. The remaining ZnO powder was classified into a size fraction ranging from 38 to 149 mum. The addition of a small amount (1 weight %) ZnO seed grains produces varistors with low breakdown voltages (7.6 V/mm) and an alpha coefficient of approximately 10. The addition of Cr2O3 stabilizes the spinel phase yielding a more homogeneous microstructure, but degraded electrical behaviour of the ZnO varistor.
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Como citar
Silicates Industriels. Mons: Belgian Ceramic Society, v. 59, n. 5-6, p. 214-216, 1994.