Effect of heat treatment on tolerance characteristic for electrical degradation of ZnO varistors with added Sb2O3
✍ Scribed by Masayuki Takada; Yuuki Sato; Shinzo Yoshikado
- Publisher
- John Wiley and Sons
- Year
- 2012
- Tongue
- English
- Weight
- 927 KB
- Volume
- 179
- Category
- Article
- ISSN
- 0424-7760
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✦ Synopsis
The effects of the heat treatment of ZnO varistors with added Bi-Mn-Co-Sb on their electrical degradation were investigated. Before heat treatment, the degree of the tolerance characteristics of varistors for electrical degradation was smallest for the sample with 0.12 mole-% of added Sb 2 O 3 . After heat treatment, the electrical degradation tolerance characteristic was markedly improved. It was found that the tolerance characteristics for electrical degradation after heat treatment strongly depend on the amount of added Sb 2 O 3 . For the samples with added Sb 2 O 3 , the tolerance characteristic for electrical degradation upon heat treatment is not affected by the intensity of the X-ray diffraction peak of the (004) plane for ZnO. For samples with 0.12 mole-% or less of added Sb 2 O 3 , the value of the nonlinearity index α of the voltage-current (V-I) characteristic after electrical degradation was proportional to the full width at half maximum (FWHM) of the X-ray diffraction peak at 29.4° for Zn 2.33 Sb 0.67 O 4 spinel particles in samples subjected to heat treatment under various conditions. Therefore, it is speculated that the increase in the FWHM for the spinel particles is due to the existence of fine spinel particles at grain boundaries or triple points of ZnO grains. Furthermore, it is speculated that the improvement of the electrical degradation tolerance characteristics is due to a decrease in the ion mobility of O 2-ions or Zn 2+ ions due to their blocking by uniformly dispersed fine spinel particles at grain boundaries.