Abstract
Microstructures of a La2O3-doped cordierite ceramic used as a low thermal expansion material were investigated by transmission electron microscopy (TEM) including energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analyses in connection with the thermal expansion properties. TEM and scanning transmission electron microscopy (STEM)-EDS revealed that cordierite grains possess accumulated dense strain, and the grain boundaries are enriched with La and Si, forming an intergranular glassy phase. In-situ TEM observation heated up to 800°C deduced that the accumulated lattice strain and the lattice parameters change with increase of temperature, although the microstructure remains almost unchanged. It was shown by conventional and interferometric dilatometry that the volume of sintered material contracts with increase of temperature, but it expands with further rise in temperature, drawing a minimum thermal expansion coefficient at around room temperature. XRD analyses revealed that the volume thermal expansion of cordierite grains is in reasonable agreement with that of the intergranular phase at a temperature of 800°C or lower, while there is a significant difference in both the expansions at higher temperature. Therefore, the unchanged grain volume around room temperature, which is caused by the contraction along the a-axis as revealed by XRD analyses, is the reason for the low thermal expansion coefficient of the sintered material. We considered that residual stresses resulting from the thermal expansion mismatches at higher temperature has little effect on the dimensional stability of the sintered material, because the presence of glass would enable stress-free conditions at temperatures above the glass transition.
| Original language | English |
|---|---|
| Title of host publication | Mechanical Properties and Performance of Engineering Ceramics and Composites VII - A Collection of Papers Presented at the 36th International Conference on Advanced Ceramics and Composites, ICACC 2012 |
| Pages | 153-162 |
| Number of pages | 10 |
| Volume | 33 |
| Edition | 2 |
| Publication status | Published - Apr 8 2013 |
| Event | Mechanical Properties and Performance of Engineering Ceramics and Composites VII - 36th International Conference on Advanced Ceramics and Composites, ICACC 2012 - Daytona Beach, FL, United States Duration: Jan 22 2012 → Jan 27 2012 |
Other
| Other | Mechanical Properties and Performance of Engineering Ceramics and Composites VII - 36th International Conference on Advanced Ceramics and Composites, ICACC 2012 |
|---|---|
| Country | United States |
| City | Daytona Beach, FL |
| Period | 1/22/12 → 1/27/12 |
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All Science Journal Classification (ASJC) codes
- Ceramics and Composites
- Materials Chemistry
Cite this
Microstructures of La-doped low thermal expansion cordierite ceramics. / Unno, Hiroto; Toh, Shoichi; Sugawara, Jun; Hattori, Kensaku; Uehara, Seiichiro; Matsumura, Syo.
Mechanical Properties and Performance of Engineering Ceramics and Composites VII - A Collection of Papers Presented at the 36th International Conference on Advanced Ceramics and Composites, ICACC 2012. Vol. 33 2. ed. 2013. p. 153-162.Research output: Chapter in Book/Report/Conference proceeding › Conference contribution
}
TY - GEN
T1 - Microstructures of La-doped low thermal expansion cordierite ceramics
AU - Unno, Hiroto
AU - Toh, Shoichi
AU - Sugawara, Jun
AU - Hattori, Kensaku
AU - Uehara, Seiichiro
AU - Matsumura, Syo
PY - 2013/4/8
Y1 - 2013/4/8
N2 - Microstructures of a La2O3-doped cordierite ceramic used as a low thermal expansion material were investigated by transmission electron microscopy (TEM) including energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analyses in connection with the thermal expansion properties. TEM and scanning transmission electron microscopy (STEM)-EDS revealed that cordierite grains possess accumulated dense strain, and the grain boundaries are enriched with La and Si, forming an intergranular glassy phase. In-situ TEM observation heated up to 800°C deduced that the accumulated lattice strain and the lattice parameters change with increase of temperature, although the microstructure remains almost unchanged. It was shown by conventional and interferometric dilatometry that the volume of sintered material contracts with increase of temperature, but it expands with further rise in temperature, drawing a minimum thermal expansion coefficient at around room temperature. XRD analyses revealed that the volume thermal expansion of cordierite grains is in reasonable agreement with that of the intergranular phase at a temperature of 800°C or lower, while there is a significant difference in both the expansions at higher temperature. Therefore, the unchanged grain volume around room temperature, which is caused by the contraction along the a-axis as revealed by XRD analyses, is the reason for the low thermal expansion coefficient of the sintered material. We considered that residual stresses resulting from the thermal expansion mismatches at higher temperature has little effect on the dimensional stability of the sintered material, because the presence of glass would enable stress-free conditions at temperatures above the glass transition.
AB - Microstructures of a La2O3-doped cordierite ceramic used as a low thermal expansion material were investigated by transmission electron microscopy (TEM) including energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analyses in connection with the thermal expansion properties. TEM and scanning transmission electron microscopy (STEM)-EDS revealed that cordierite grains possess accumulated dense strain, and the grain boundaries are enriched with La and Si, forming an intergranular glassy phase. In-situ TEM observation heated up to 800°C deduced that the accumulated lattice strain and the lattice parameters change with increase of temperature, although the microstructure remains almost unchanged. It was shown by conventional and interferometric dilatometry that the volume of sintered material contracts with increase of temperature, but it expands with further rise in temperature, drawing a minimum thermal expansion coefficient at around room temperature. XRD analyses revealed that the volume thermal expansion of cordierite grains is in reasonable agreement with that of the intergranular phase at a temperature of 800°C or lower, while there is a significant difference in both the expansions at higher temperature. Therefore, the unchanged grain volume around room temperature, which is caused by the contraction along the a-axis as revealed by XRD analyses, is the reason for the low thermal expansion coefficient of the sintered material. We considered that residual stresses resulting from the thermal expansion mismatches at higher temperature has little effect on the dimensional stability of the sintered material, because the presence of glass would enable stress-free conditions at temperatures above the glass transition.
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M3 - Conference contribution
AN - SCOPUS:84875713785
SN - 9781118205884
VL - 33
SP - 153
EP - 162
BT - Mechanical Properties and Performance of Engineering Ceramics and Composites VII - A Collection of Papers Presented at the 36th International Conference on Advanced Ceramics and Composites, ICACC 2012
ER -