Low-Temperature Fabrication of Cordierite Ceramics from Kaolinite and Magnesium Hydroxide Mixtures with Boron Oxide Additions |
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Authors: | Katsuhiro Sumi Yuichi Kobayashi Etsuro Kato |
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Affiliation: | Department of Applied Chemistry, Aichi Institute of Technology, Yachigusa, Aichi 470–0392, Japan |
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Abstract: | Thermal reactions of mixtures of ultrafine particles of magnesium hydroxide (Mg(OH)2) and kaolinite in a composition of MgO:Al2O3:2SiO2 were investigated to obtain dense cordierite ceramics at temperatures <1000°C. While heating the mixture of kaolinite and Mg(OH)2 with the equivalent of 2 mass% of boron oxide (B2O3) (in the form of magnesium borate, 2MgOB2O3), an amorphous phase formed at a temperature of ~850°C after thermal decomposition. Firing the mixture at a temperature of 900°C yielded dense ceramics with an apparent porosity of almost zero. The addition of B2O3 promoted the densification at 850°-900°C and accelerated the crystallization of alpha-cordierite. The specimen with 3 mass% of B2O3 that was fired at a temperature of 950°C showed a linear thermal expansion coefficient of ~3 × 10?6 K?1, a bending strength of >200 MPa, and a relative dielectric constant of 5.5 at 1 MHz. These cordierite ceramics may be used as substrate materials for semiconductor interconnection applications. |
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