The effect of lithium oxide on the threshold field of ZnO varistors
Lithium oxide in form of Li 2CO 3 solution is added with contents of 0–200 ppm to two ZnO-based varistors standard formulations, once with Sb 2O 3 and the other without. According to Li 2CO 3 concentration, both threshold field and energy absorption capability evolution are studied. It is found that...
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Veröffentlicht in: | Ceramics international 2009-05, Vol.35 (4), p.1385-1389 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | Lithium oxide in form of Li
2CO
3 solution is added with contents of 0–200
ppm to two ZnO-based varistors standard formulations, once with Sb
2O
3 and the other without. According to Li
2CO
3 concentration, both threshold field and energy absorption capability evolution are studied. It is found that with the benefit of antimony, the lithium allows reaching high threshold field but concomitantly, low energy absorption capability. Without antimony, threshold fields up to 300
V/mm are attained, associated with a fair energy absorption capability. With 100
ppm of Li
2CO
3, optimum couple of values (315
V/mm; 115
J/cm
3) is achieved. With 200
ppm of Li
2CO
3, threshold field exceeds 500
V/mm but energy absorption capability falls below 50
J/cm
3. Correlations with SEM microstructures observations suggest that lithium increases voltage barrier height by decreasing donor density and that spinel phases (Zn
7Sb
2O
12) have detrimental effects on the electrical absorption capability by limiting the density of current, reducing the effective current path from one ZnO grain to another. |
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ISSN: | 0272-8842 1873-3956 |
DOI: | 10.1016/j.ceramint.2008.07.009 |