ja6b08746_si_001.pdf (1.43 MB)
Atomic Linkage Flexibility Tuned Isotropic Negative, Zero, and Positive Thermal Expansion in MZrF6 (M = Ca, Mn, Fe, Co, Ni, and Zn)
journal contribution
posted on 2016-10-26, 00:00 authored by Lei Hu, Jun Chen, Jiale Xu, Na Wang, Fei Han, Yang Ren, Zhao Pan, Yangchun Rong, Rongjin Huang, Jinxia Deng, Laifeng Li, Xianran XingThe controllable
isotropic thermal expansion with a broad coefficient
of thermal expansion (CTE) window is intriguing but remains challenge.
Herein we report a cubic MZrF6 series (M = Ca, Mn, Fe,
Co, Ni and Zn), which exhibit controllable thermal expansion over
a wide temperature range and with a broader CTE window (−6.69
to +18.23 × 10–6/K). In particular, an isotropic
zero thermal expansion (ZTE) is achieved in ZnZrF6, which
is one of the rarely documented high-temperature isotropic ZTE compounds.
By utilizing temperature-dependent high-energy synchrotron X-ray total
scattering diffraction, it is found that the flexibility of metal···F
atomic linkages in MZrF6 plays a critical role in distinct
thermal expansions. The flexible metal···F atomic linkages
induce negative thermal expansion (NTE) for CaZrF6, whereas
the stiff ones bring positive thermal expansion (PTE) for NiZrF6. Thermal expansion could be transformed from striking negative,
to zero, and finally to considerable positive though tuning the flexibility
of metal···F atomic linkages by substitution with a
series of cations on M sites of MZrF6. The present study
not only extends the scope of NTE families and rare high-temperature
isotropic ZTE compounds but also proposes a new method to design systematically
controllable isotropic thermal expansion frameworks from the perspective
of atomic linkage flexibility.