Microstructures of La-doped low thermal expansion cordierite ceramics

Hiroto Unno, Shoichi Toh, Jun Sugawara, Kensaku Hattori, Seiichiro Uehara, Syo Matsumura

研究成果: Chapter in Book/Report/Conference proceedingConference contribution

1 被引用数 (Scopus)

抄録

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.

本文言語英語
ホスト出版物のタイトル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
ページ153-162
ページ数10
33
2
出版ステータス出版済み - 4 8 2013
イベントMechanical Properties and Performance of Engineering Ceramics and Composites VII - 36th International Conference on Advanced Ceramics and Composites, ICACC 2012 - Daytona Beach, FL, 米国
継続期間: 1 22 20121 27 2012

その他

その他Mechanical Properties and Performance of Engineering Ceramics and Composites VII - 36th International Conference on Advanced Ceramics and Composites, ICACC 2012
国/地域米国
CityDaytona Beach, FL
Period1/22/121/27/12

All Science Journal Classification (ASJC) codes

  • セラミックおよび複合材料
  • 材料化学

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