Microstructures of La-doped low thermal expansion cordierite ceramics

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

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Citation (Scopus)

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 languageEnglish
Title of host publicationMechanical 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
Pages153-162
Number of pages10
Volume33
Edition2
Publication statusPublished - Apr 8 2013
EventMechanical 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 2012Jan 27 2012

Other

OtherMechanical Properties and Performance of Engineering Ceramics and Composites VII - 36th International Conference on Advanced Ceramics and Composites, ICACC 2012
Country/TerritoryUnited States
CityDaytona Beach, FL
Period1/22/121/27/12

All Science Journal Classification (ASJC) codes

  • Ceramics and Composites
  • Materials Chemistry

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