Authors : A. Djelloul , A. Boumaza , N. Bouzid , A. Mahdjoub and L. Hadjeris
Abstract: ZnO-Bi2O3-based varistor samples doped with 2.0 mol% of (Cr2O3+SiO2) and varying amounts of Al2O3 in the range from 7.0 to 1.0 mol% were fired at 1200�C for 2h. Anew process is described for achieving the current-voltage characteristics ofa low voltage ZnO varistor. Second phases, segregated and precipitated in ZnO-based varistors, encountered in triple junctions and grain boundaries regions were identified using XRD, SEM and energy dispersive spectrometry. Using IR spectroscopy we have observed OH and H2O molecular stretch modes at 3444.24 cm-1 with a width of 273.53 cm-1 and near 1637.27 cm-1 with a width of 42.64 cm-1 respectively. The hydrogen in Al doped ZnO-Bi2O3-based varistor may have a one site preference, resulting in a wider OH peak. The band at 662 cm-1 should be due to the presence of the ZnAl2O4 spinel, undoubtedly identified in the XRD patterns of sintered ceramics. Addition of hydrogen to aluminium doped varistors slow down the grain growth effect.
A. Djelloul , A. Boumaza , N. Bouzid , A. Mahdjoub and L. Hadjeris , 2006. Microstructural and Characteristics Study of Low Voltage ZnO-Bi2O3-Based Varistor Doped with Cr2O3, SiO2 and Varying Amounts of Al2O3. Asian Journal of Information Technology, 5: 1248-1255.