Helium Incorporation into Scandium Fluoride, a Model Negative Thermal Expansion Material.

ABSTRACT: Scandium trifluoride is a model negative thermal expansion (NTE) material. Its simple structure can be described as an A-site vacant perovskite, and it shows isotropic NTE over a very wide temperature range (up to ∼1100 K), due to transverse vibrational motion of the fluoride. Like many framework NTE materials, it undergoes a phase transition at low pressures, adopting a rhombohedral (R3̅c) structure at >0.7 GPa and 300 K in commonly used nonpenetrating pressure media, such as silicone oil. High pressure X-ray diffraction data and gas uptake/release measurements indicate that, on compression in helium above ∼200 K, helium is inserted into ScF₃ to form the defect perovskite He _x ScF₃. The incorporation of helium stiffens the structure an

SUBMITTER: Ma S 

PROVIDER: S-EPMC11866548 | biostudies-literature | 2025 Feb

REPOSITORIES: biostudies-literature