Distribution of chemical elements in a zinc oxide ceramic for varistors
The authors used x-ray spectral microanalysis to investigate the distribution of Zn, Bi, Sb, Co, and Mn in a ceramic for varistors based on ZnO with additives. Specimens of composition (mole %) 97.5 ZnO, 1 Sb/sub 2/O/sub 3/, 0.5 Bi/sub 2/O/sub 3/, 0.5 Co/sub 3/O/sub 4/, and 0.5 MnO/sub 2/ were prepared by sintering under oxidative conditions. X-ray spectral microanalysis was carried out with a Cambridge Stereoscan S4 scanning electron microscopy with intersection of the specimen surface by the electron beam and superposition of the obtained distribution of the intensity surface region under conditions of secondary electron emission and also with fixation of the electron probe and comparison of the intensity of radiation of different elements in a chosen point of the specimen. The authors observed inhomogeneity of the chemical composition of the intergranular phases in the ceramic based on the ZnO-Bi/sub 2/O/sub 3/-Sb/sub 2/O/sub 3/-Co/sub 3/O/sub 4/-MnO/sub 2/ system and a higher content of CO and Mn in the intergranular phase than in the zinc oxide grains. An increase of the fraction of higher-valence transition-metal ions in the vitrifying and crystallizing intergranular phases during cooling of the body being sintered led to a decrease of the Fermi level in the grain-boundary region and to the formation of potential barriers determining the low conductivity in a weak field and the field dependence of the conductivity of the ceramic.
- Research Organization:
- Dnepropetrovsk State Univ. (USSR)
- OSTI ID:
- 6012034
- Journal Information:
- Inorg. Mater. (Engl. Transl.); (United States), Journal Name: Inorg. Mater. (Engl. Transl.); (United States) Vol. 24:7; ISSN INOMA
- Country of Publication:
- United States
- Language:
- English
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ANTIMONY
ANTIMONY COMPOUNDS
ANTIMONY OXIDES
BISMUTH
BISMUTH COMPOUNDS
BISMUTH OXIDES
CERAMICS
CHALCOGENIDES
CHEMICAL COMPOSITION
COBALT
COBALT COMPOUNDS
COBALT OXIDES
CRYSTAL STRUCTURE
DISTRIBUTION
ELECTRIC CONDUCTIVITY
ELECTRICAL EQUIPMENT
ELECTRICAL PROPERTIES
ELECTRON MICROSCOPY
ELEMENTS
EMISSION
EQUIPMENT
FABRICATION
GRAIN BOUNDARIES
MANGANESE
MANGANESE COMPOUNDS
MANGANESE OXIDES
MASS DISTRIBUTION
MATERIALS TESTING
METALLURGICAL EFFECTS
METALS
MICROSCOPY
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
PHYSICAL PROPERTIES
POROSITY
QUANTITY RATIO
RESISTORS
SCANNING ELECTRON MICROSCOPY
SECONDARY EMISSION
SEMICONDUCTOR DEVICES
SEMICONDUCTOR RESISTORS
SINTERING
SPATIAL DISTRIBUTION
SPECTROSCOPY
TESTING
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
X-RAY SPECTROSCOPY
ZINC
ZINC COMPOUNDS
ZINC OXIDES