Importance of oxygen atmosphere to recover the ZnO-based varistors properties
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A methodology to recover the non-ohmic properties of ZnO based varistors after degradation with long and short duration pulses was proposed in this work. The basic idea consists in submitt the degraded ceramics at different temperatures and oxygen flows. Thermal treatment at 900 °C for 2 h with oxygen flow of 15 l/h allowed to obtain better non-linear coefficient (α = 52.5) compared to the standard sample. Rietveld refinement showed that with the thermal treatment, the oxygen species and the β-Bi2O3 phase, lost in the degradation process, are recovered in the grain boundary.
KeywordsBi2O3 Rietveld Refinement Oxygen Flow Bismuth Oxide Enrich Oxygen
Mastery in Engineering of Materials and Process, DIME, Faculty of Mines and Academic Direction of the National University of Colombia-Sede Medellín by the financial support of this research and the facilities offered by CMDMC-LIEC at the Chemistry Institute-UNESP and Department of Chemistry-UFSCar. The authors thank A.A Cavalheiro for his help with Rietveld’s analyze.
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