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Microstructure and Crystal Structure of Bismuth Oxide Phases in Zinc Oxide Varistor Ceramics
Author(s) -
CERVA HANS,
RUSSWURM WINFRIED
Publication year - 1988
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.1151-2916.1988.tb05915.x
Subject(s) - materials science , bismuth , microstructure , tetragonal crystal system , ceramic , oxide , crystal structure , transmission electron microscopy , phase (matter) , crystallography , stoichiometry , mineralogy , metallurgy , nanotechnology , chemistry , organic chemistry
The microstructure and crystal structure of bismuth oxide phases of as‐sintered and additionally heat‐treated ZnO varistor ceramics was examined by means of transmission electron microscopy and X‐ray powder diffraction. Grains of β‐Bi 2 O 3 present in as‐sintered samples were found to consist of two types of domains which have the same basic tetragonal lattice. They can, however, be distinguished by the contrast between local strain centers due to microdefects present in one domain. Some multiple‐grain junctions contained both α‐ and β‐Bi 2 O 3 grains. Heat treatment induces a transformation of the α‐ and β‐Bi 2 O 3 phases into γ‐Bi 2 O 3 . A clear crystallographic relationship between the transforming phases β to γ is shown. The β‐Bi 2 O 3 phase was also found to transform into the non‐stoichiometric crystalline Bi 2 O 2.33 phase.