School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
J Am Chem Soc. 2010 Nov 10;132(44):15496-8. doi: 10.1021/ja106711v.
Scandium trifluoride maintains a cubic ReO(3) type structure down to at least 10 K, although the pressure at which its cubic to rhombohedral phase transition occurs drops from >0.5 GPa at ∼300 K to 0.1-0.2 GPa at 50 K. At low temperatures it shows strong negative thermal expansion (NTE) (60-110 K, α(l) ≈ -14 ppm K(-1)). On heating, its coefficient of thermal expansion (CTE) smoothly increases, leading to a room temperature CTE that is similar to that of ZrW(2)O(8) and positive thermal expansion above ∼1100 K. While the cubic ReO(3) structure type is often used as a simple illustration of how negative thermal expansion can arise from the thermally induced rocking of rigid structural units, ScF(3) is the first material with this structure to provide a clear experimental illustration of this mechanism for NTE.
三氟化钪在至少 10 K 下保持立方 ReO(3) 型结构，尽管其立方相向菱方相转变发生的压力从约 300 K 时的>0.5 GPa 下降到 50 K 时的 0.1-0.2 GPa。在低温下，它表现出强烈的负热膨胀（NTE）（60-110 K，α(l) ≈ -14 ppm K(-1)）。在加热过程中，其热膨胀系数（CTE）平滑增加，导致室温 CTE 与 ZrW(2)O(8)相似，在约 1100 K 以上出现正热膨胀。虽然立方 ReO(3)结构类型通常被用作热诱导刚性结构单元的摇摆如何导致负热膨胀的简单说明，但 ScF(3) 是第一个具有这种结构的材料，为 NTE 的这种机制提供了明确的实验说明。
