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Deep Level Transient Spectroscopy of Zinc Oxide Varistors Doped with Aluminum Oxide and/or Silver Oxide
Author(s) -
Fan Jiwei,
Freer Robert
Publication year - 1994
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1994.tb04659.x
Subject(s) - varistor , doping , materials science , zinc , deep level transient spectroscopy , analytical chemistry (journal) , dopant , penning trap , oxide , aluminium , trap (plumbing) , chemistry , metallurgy , silicon , optoelectronics , ion , electrical engineering , environmental engineering , engineering , organic chemistry , chromatography , voltage
Deep level transient spectroscopy was employed to investigate the effect of two different dopants (aluminum and silver) on the electronic states of ZnO varistors. The base composition was a typical commercial formulation, and specimens were prepared by the mixed oxide route. Two electron traps were detected: trap L 1 , ( E c − 0.15 ± 0.01 eV) and trap L 2 ( E c − 0.25 ± 0.01 eV). Doping specimens with trivalent Al increased the densities of both traps; such varistors have improved nonlinearity characteristics, but lower stability. In contrast, doping with monovalent Ag decreased the trap densities, reduced the nonlinearity exponents, but increased stability. Specimens containing an optimum combination of Al and Ag doping had a high L 1 , trap density, a low L 2 trap density, and exhibited good nonlinearity and stability characteristics. The L 1 , trap appears to be associated with extrinsic donor defects, reflecting varistor non‐linearity; L 1 , trap density increased with nonlinearity exponents. The L 2 trap appears to be associated with varistor stability. As the L 2 trap density decreased, the sample stability increased; this may reflect the concentration of zinc interstitial defects.