Distribution of chemical elements in a zinc oxide ceramic for varistors

Journal Article · Thu Dec 01 00:00:00 EST 1988 · Inorg. Mater. (Engl. Transl.); (United States)

OSTI ID:6012034

Glot, A B

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), Vol. 24:7; Other Information: Translated from Izv. Akad. Nauk. SSSR, Neorg. Mater.; 24: No. 7, 1231-1232 (Jul 1988)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
METALS
MASS DISTRIBUTION
SEMICONDUCTOR RESISTORS
MATERIALS TESTING
ZINC OXIDES
GRAIN BOUNDARIES
ANTIMONY
ANTIMONY OXIDES
BISMUTH
BISMUTH OXIDES
CERAMICS
CHEMICAL COMPOSITION
COBALT
COBALT OXIDES
ELECTRIC CONDUCTIVITY
MANGANESE
MANGANESE OXIDES
METALLURGICAL EFFECTS
PHASE STUDIES
POROSITY
QUANTITY RATIO
SCANNING ELECTRON MICROSCOPY
SECONDARY EMISSION
SINTERING
X-RAY SPECTROSCOPY
ZINC
ANTIMONY COMPOUNDS
BISMUTH COMPOUNDS
CHALCOGENIDES
COBALT COMPOUNDS
CRYSTAL STRUCTURE
DISTRIBUTION
ELECTRICAL EQUIPMENT
ELECTRICAL PROPERTIES
ELECTRON MICROSCOPY
ELEMENTS
EMISSION
EQUIPMENT
FABRICATION
MANGANESE COMPOUNDS
MICROSCOPY
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RESISTORS
SEMICONDUCTOR DEVICES
SPATIAL DISTRIBUTION
SPECTROSCOPY
TESTING
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
ZINC COMPOUNDS
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies
360204 - Ceramics
Cermets
& Refractories- Physical Properties