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
Hauptverfasser: Houabes, Mourad, Metz, Renaud
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.
ISSN:0272-8842
1873-3956
DOI:10.1016/j.ceramint.2008.07.009