Dissemination of IT for the Promotion of Materials Science (DoITPoMS)

DoITPoMS Micrograph Library Full Record for Micrograph 199

Full Record for Micrograph 199

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Micrograph no
199
Brief description
BaTiO3 Temperature-stable dielectric capacitor
Keywords
alumina Link to MATTER Glossary entry for alumina, ceramic Link to MATTER Glossary entry for ceramic, engineering ceramic
Categories
Ceramic
System
BaTiO3 + other oxides such as Nb2O5, Bi2O3
Composition
BaTiO3 95-97 (wt%)
Standard codes
Reaction
Processing
Fine oxide additives react with BaTiO3 powder forming a series of phases which act as the source for the dopants.
Applications
Temperature stable X7R capacitors in millions of electrical circuits.
Sample preparation
Grind, polish, ion thin and carbon coat.
Technique
Bright-field TEM
Length bar
1 μm
Further information
The image shows a single representative grain within the polycrystalline ceramic. The core region shows ferroelectric domains from the pure, tetragonal BaTiO3 centre. The shell region contains Nb and Bi dopant which make it cubic, paraelectric and also stacking faults associated with their presence. The heterogeneous nature of the microstructure confers the temperature stability on the ceramic.
Contributor
Prof W E Lee
Organisation
Department of Engineering Materials, University of Sheffield
Date
02/09/02
Licence for re-use
Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales