Rapid Molten Salt Synthesis of Isotropic Negative Thermal Expansion ScF3

With a simple ReO₃‐type structure, ScF₃ exhibits a rare property of isotropic negative thermal expansion over a large temperature range. In this study, a rapid and low‐temperature synthesis route has been developed to prepare pure phase of ScF₃ in which NaNO₃ or KNO₃ as reaction media and Sc(NO₃)₃ and NH₄HF₂ as precursors (i.e., 30 min and 310°C). The sample of ScF₃ has relatively regular morphology and shows high crystallinity as well as single‐crystalline nature. The type of molten salts has obvious impact on morphologies of the particles. Substituting NaNO₃ with KNO₃, cubes of ScF₃ turns to be nanosticks. The thermal stability of the as‐prepared ScF₃ was investigated by thermal analysis. Molten salts play a significant role in eliminating the nonstoichiometric impurity of ScF_2.76 which is a common impurity during the conventional chemical reaction. This study reveals that molten salt is in favor of preparing those fluorides and relatives which is inert with moisture.