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首页> 外文会议>Mechanical properties and performance of engineering ceramics and composites VII >MICROSTRUCTURES OF La-DOPED LOW THERMAL EXPANSION CORD1ER1TE CERAMICS
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MICROSTRUCTURES OF La-DOPED LOW THERMAL EXPANSION CORD1ER1TE CERAMICS

机译：La掺杂的低热膨胀率CORD1ER1TE陶瓷的微观结构

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Microstructures of a La_2O_3-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, ln-situ TEM observation heated up to 800 ℃ 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 ℃ 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.
机译：通过透射电子显微镜（TEM），包括能量分散光谱（EDS）和X射线衍射（XRD）分析，研究了用作低热膨胀材料的La_2O_3掺杂堇青石陶瓷的微观结构。 TEM和扫描透射电子显微镜（STEM）-EDS显示堇青石晶粒具有累积的致密应变，且晶界富含La和Si，形成晶间玻璃态相，原位TEM观察加热至800℃可推断出尽管微观结构几乎保持不变，但累积的晶格应变和晶格参数随温度的升高而变化。传统的和干涉式膨胀法表明，烧结材料的体积随着温度的升高而收缩，但随着温度的进一步升高而膨胀，从而在室温附近获得最小的热膨胀系数。 XRD分析表明，在800℃以下，堇青石晶粒的体积热膨胀与晶间相的体积热膨胀基本吻合，而在较高温度下，两者的膨胀都有显着差异。因此，如XRD分析所揭示的那样，由于沿a轴的收缩而引起的室温附近的晶粒体积的不均是烧结材料的热膨胀系数低的原因。我们认为，由高温下的热膨胀失配引起的残余应力对烧结材料的尺寸稳定性几乎没有影响，因为玻璃的存在将在高于玻璃化转变温度的条件下实现无应力条件。

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  • 会议地点 Daytona Beach FL(US);Daytona Beach FL(US);Daytona Beach FL(US)
  • 作者

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

  • 作者单位

    Ceramics Division, Krosaki Harima Corporation, Fukuoka 806-8586, Japan;

    HVEM Laboratory, Kyushu University, Fukuoka 819-0395, Japan;

    Ceramics Division, Krosaki Harima Corporation, Fukuoka 806-8586, Japan;

    Ceramics Division, Krosaki Harima Corporation, Fukuoka 806-8586, Japan;

    Department of Earth and Planetary Sciences, Kyushu University, Fukuoka 812-8581, Japan;

    HVEM Laboratory, Kyushu University, Fukuoka 819-0395, Japan,Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Fukuoka 819-0395, Japan;

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