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Micrograph 152 and full record

Link to image file for micrograph 152
Micrograph no
152
Brief description
Barium Hexaferrite
Keywords
barium, barium hexaferrite, carbon, ceramic Link to MATTER Glossary entry for ceramic, ferrite Link to MATTER Glossary entry for ferrite, granule, hard magnet Link to MATTER Glossary entry for hard magnet, iron, oxygen Link to MATTER Glossary entry for oxygen
Categories
Ceramic
System
BaO-Fe2O3
Composition
BaO . 6Fe2O3
Standard codes
Reaction
Processing
BaCO3 and Fe2O3 powders are calcined to form BaO.6Fe2O3 and then spray dried to produce granules or controlled spherical agglomerates which pack well during die pressing. After shape forming the green compact is fired at about 1250 °C.
Applications
Magnetically hard ferrites (confusingly the general name for magnetic ceramics) have strong permanent magnetisation. Uses are many but include mixing with plastic to provide a flexible strip seal around e.g. refrigerators and in electricity meters to support the rotor to reduce bearing wear.
Sample preparation
Polished but unetched.
Technique
Reflected light microscopy
Length bar
100 μm
Further information
The porosity (dark) level is high since in use strength is not a priority. The original granule size (about 30 micrometre diameter) is easily visualised since extensive intergranular porosity is present.
Contributor
Prof W E Lee
Organisation
Department of Engineering Materials, University of Sheffield
Date
10/05/02
Licence for re-use
Attribution-NonCommercial-ShareAlike 4.0 International

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