Abstract
Materials with negative coefficients of thermal expansion (CTEs) can be used to prepare composites with specific CTE values. Negative thermal expansion behavior can be primarily attributed to two types of mechanisms: phase transition- and framework-type mechanisms. This paper reports Zr2SP2O12, which has unique negative thermal expansion behavior involving both mechanisms. Zr2SP2O12 undergoes a framework-type mechanism at temperatures <393 K or >453 K and an isosymmetric phase transition at 393–453 K. The volumetric CTE of α-Zr2SP2O12 is ~−70 p.p.m./K during the isosymmetric phase transition, and this value can be decreased by decreasing the proportion of sulfur. The minimum volumetric CTE of α-Zr2S0.9P2O12-δ is ~−108 p.p.m./K in the temperature range of 393–453 K. Between 303 and 773 K, the volume of α-Zr2S0.9P2O12 − δ is reduced by ~1.3%. Finally, this paper presents methods for the hydrothermal synthesis of α-Zr2SP2O12 and for controlling the sulfur content.
Highlights
Materials with negative coefficients of thermal expansion (CTEs) are useful for preparing composites with controllable thermal expansion behaviors
The data suggest an enthalpy of ~−3.6 mJ/mol, much smaller than the phase transition enthalpies of typical ceramics (e.g., ~−35 J/mol for the tetragonal-to-monoclinic phase transition of ZrO2)[26]
To confirm the phase transition, changes in atomic coordination were estimated using the Rietveld method based on the powder X-ray diffraction (PXRD) patterns (Supplementary Tables S8– 18) and visualized in VESTA 327
Summary
Materials with negative coefficients of thermal expansion (CTEs) are useful for preparing composites with controllable thermal expansion behaviors. The mechanisms active in these materials with negative CTEs can be classified into three categories: atomic radius contraction, magneto-volume effect, and framework-type mechanisms[1,2,3,4,5,6,7]. The CTEs of these materials are positive at temperatures outside the temperature range of the phase transition, while they exhibit excellent performance within the temperature range of the phase transition[8]. These thermal properties might lead to problems when composites containing phase transition-type negative CTE fillers are exposed to unexpected temperatures.
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