Otro
Microstructural development of ZnO varistor during reactive liquid phase sintering
Registro en:
Journal of Materials Science, v. 31, n. 20, p. 5391-5398, 1996.
0022-2461
10.1007/BF01159308
WOS:A1996VP57100015
2-s2.0-0030261880
0000-0003-4843-3975
Autor
Leite, E. R.
Nobre, Marcos Augusto Lima
Longo, Elson
Varela, José Arana
Resumen
The microstructural evolution, grain growth and densification for the varistor systems ZnO-Bi2O3 (ZB), ZnO-Bi2O3-Sb2O3 (ZBS), ZnO-Bi2O3-Sb2O3-MnO-Cr 2O3-CoO (ZBSCCM) were studied using constant heating rate sintering, scanning electron microscopy (SEM) and in situ phase formation measurement by high temperature X-ray diffraction (HT-XRD). The results showed that the densifying process is controlled by the formation and decomposition of the Zn2Bi3Sb3O14 pyrochlore (PY) phase for the ZBS and ZBSCCM systems. The addition of transition metals (ZBSCCM system) alters the formation and decomposition reaction temperatures of the pyrochlore phase and the morphology of the Zn7Sb2O12 spinel phase. Thus, the spinel grains act as inclusions and decrease the ZnO grain growth rate. Spinel grain growth kinetics in the ZBSCCM system showed an n value of 2.6, and SEM and HT-XRD results indicate two grain growth mechanisms based on coalescence and Ostwald ripening. © 1996 Chapman & Hall.