LaFeAsO纳米晶的中低温合成与表征

研究了铁基超导母体化合物LaFeAsO的低温固相反应合成及表征。实验以La₂O₃、LaCl₃以及BaFe₂As₂为原料, 通过球磨混合, 成功地在中低温(~500℃)下实现固相反应, 从而获得LaFeAsO纳米晶。采用X射线衍射Scherrer公式, 估算其平均晶粒尺寸小于100 nm。低温电阻测量表明, LaFeAsO纳米晶的自旋密度波反常变得不显著, 且其转变温度明显下降。采用晶粒尺寸效应和晶胞参数影响对这种现象进行了解释。

Low-temperature Synthesis and Characterizations of LaFeAsO Nanocrystals

LaFeAsO as a parent compound of iron-based superconductor was synthesized at low temperatures. The mixtures of La₂O₃, LaCl₃ and BaFe₂As₂ were ball-milled and the pressed pellets were sintered at 500℃ in vacuum. And nanocrystals of LaFeAsO were formed during the solid-state reaction. The solid-state reaction temperature for preparing LaFeAsO is 200℃ lower than the literature reported. The average crystallite size of the as-prepared LaFeAsO is less than 100 nm, as estimated by the X-ray diffraction Scherrer formula. Meanwhile, the c axis of the unit cell is increased by 0.001 nm, primarily stemming from the nanosize effect. Electrical resistivity measurement shows that the spin-density-wave anomaly becomes unremarkable, accompanied by a significant decrease in the transition temperature. The phenomena are discussed in terms of crystallite-size effect and the influence of lattice parameters.