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Effect of Doping on the Thermal Expansion of β-Eucryptite Prepared by Sol–Gel Methods

Authors

  • Subramanian Ramalingam,

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    • Colorado Center for Advanced Ceramics, Department of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, CO
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  • Ivar E. Reimanis

    1. Colorado Center for Advanced Ceramics, Department of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, CO
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Author to whom correspondence should be addressed. e-mail: reimanis@mines.edu

Abstract

The thermal expansion behavior of pure β-eucryptite and Zn-doped β-eucryptite (substituting Zn for Li), prepared using sol–gel methods and hot pressing, were investigated. β-eucryptite exhibits an anisotropic negative coefficient of thermal expansion (CTE), which leads to microcrack formation in sintered polycrystalline samples. This is manifested by the presence of a hysteresis in the thermal expansion curves. The hysteresis disappears when a small amount of Zn (0.5–3 mol% Zn) is present. Furthermore, the bulk CTE increases significantly in magnitude (from −4 × 10−6/°C for pure β-eucryptite to 1 × 10−6/°C to 2 × 10−6/°C), and is slightly positive in the range from 25°C to 1000°C. No difference in grain size was observed between the pure and doped samples, and all the ceramics exhibited high relative densities. It is likely that Zn substitutes for Li in the β-eucryptite structure and reduces the c-axis thermal expansion, thereby lowering the CTE anisotropy and lowering the tendency for microcracking.

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