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Deep Levels Near the Grain Boundary in a Zinc Oxide Varistor: Energy Change Due to Electrical Degradation
Author(s) -
Tanaka Junzo,
Hishita Shunichi,
Okushi Hideyo
Publication year - 1990
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.1151-2916.1990.tb05217.x
Subject(s) - varistor , grain boundary , materials science , isothermal process , deep level transient spectroscopy , degradation (telecommunications) , zinc , thermal conduction , capacitance , activation energy , condensed matter physics , mineralogy , composite material , metallurgy , chemistry , electrical engineering , electrode , thermodynamics , voltage , microstructure , physics , organic chemistry , silicon , engineering
Localized deep levels in a ZnO varistor were investigated by isothermal capacitance transient spectroscopy, in relation to a degradation of nonlinear electrical characteristics caused by thermal treatment in a slightly reduced atmosphere. Two discrete deep levels were observed near the grain boundary. Before the degradation, they were located at 0.36 and 0.19 eV below a conduction band. After the degradation, they shifted toward the conduction band by 0.16 and 0.09 eV, respectively: the energy shift was not identical for the two levels. It was suggested that the energy shift of the localized levels reflected lattice disorders originally existing near the grain boundary or proper changes of chemical states induced by the reduction.