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Characterization of Ultra-fine Grained and Nanocrystalline Materials Using Transmission Kikuchi Diffraction
Published on: April 1, 2017
Lattice parameter determination of mullite by energy-filtered needle-texture electron diffraction pattern
Sujeong Lee1, Yoon Joong Kim, Hyeong-Tae Jou
1Reliability Assessment & Materials Evaluation Center, Korea Institute of Ceramic Engineering and Technology, Seoul 153-801, Korea. crystal@kicet.re.kr
Journal of Electron Microscopy
|February 8, 2005
Summary
Pyrophyllite transforms into mullite through topotaxy upon heating. This study fully interpreted mullite
Area of Science:
- Mineralogy
- Materials Science
- Solid-State Chemistry
Background:
- Pyrophyllite is a 2:1 phyllosilicate mineral.
- Mullite is a key ceramic material known for its high-temperature stability.
- Understanding the transformation pathway is crucial for controlling material properties.
Purpose of the Study:
- To re-examine the thermal transformation of pyrophyllite to mullite.
- To fully interpret the texture electron diffraction pattern of mullite.
- To elucidate the topotactic transformation mechanism.
Main Methods:
- Energy-filtering transmission electron microscopy (EFTEM)
- Texture electron diffraction pattern analysis
- High-temperature heating experiments
Main Results:
- Pyrophyllite dehydroxylate maintains long-range order up to 1000°C.
- Topotactic transformation to mullite occurs gradually.
- Mullite needles grow rapidly and randomly at 1200°C.
- Amorphous silica crystallizes to cristobalite at 1300°C.
- Mullite needles align along the b(*)-axis of pyrophyllite dehydroxylate.
- Mullite exhibits monoclinic symmetry, differing from orthorhombic 3/2-mullite.
Conclusions:
- The thermal transformation of pyrophyllite to mullite is a topotactic process.
- The structural affiliation to pyrophyllite dehydroxylate influences the resulting mullite structure.
- Detailed microstructural analysis provides insights into ceramic phase transformations.
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