新型锕系化合物Gd_0.95U_0.05FeAsO的制备与性能研究

Synthesis and Properties of Novel Actinide Compound Gd_0.95U_0.05FeAsO

摘要: 铁基超导体作为继铜氧化物超导体之后的第二类高温超导体系，因其独特的晶体结构与丰富的物理效应，在新型超导材料探索及超导机理研究中占据重要地位。本研究在GdFeAsO体系中采用铀(U)部分取代钆(Gd)，成功制备出一种新型锕系化合物Gd_0.95U_0.05FeAsO材料。X射线衍射测试结果表明，U掺杂会使晶体a轴与c轴晶格参数均收缩，证实U原子有效取代晶格中Gd原子。成分分析表征显示U元素在基体中均匀分布，仅生成微量UO₂杂质相。通过氩气及空气气氛对照实验及热力学分析可知，惰性气氛或真空储存可明显降低该材料氧化的风险，空气热处理时738 K (As₂O₃沸点)是需重点控制的临界温度，高于该温度会加速Fe位点氧化放热。母体化合物在128 K附近出现显著的电阻率反常现象，该特征与自旋密度波失稳行为密切相关；U掺杂可有效抑制自旋密度波失稳，并使Gd_0.95U_0.05FeAsO化合物出现零电阻现象。霍尔效应测试进一步证实，U掺杂会向该体系中引入电子型载流子。

Abstract: As the second family of high-temperature superconductors following cuprates, iron-based superconductors occupy a vital position in the exploration of novel superconducting materials and the investigation of superconducting mechanisms owing to their distinctive crystal structures and abundant physical phenomena. In this work, uranium (U) was adopted to partially substitute gadolinium (Gd) in the GdFeAsO system, and a new actinide compound Gd_0.95U_0.05FeAsO was successfully synthesized. X-ray diffraction measurements reveal that U doping induces lattice contraction along both the a-axis and c-axis, verifying that U atoms effectively replace Gd atoms in the crystal lattice. Elemental mapping characterizations demonstrate uniform distribution of U within the matrix, with only trace amounts of UO₂ impurity phase formed. Comparative experiments under argon and air atmospheres combined with thermodynamic analysis indicate that storage under an inert atmosphere or vacuum can substantially mitigate oxidation of the material. During thermal treatment in air, 738 K (the boiling point of As₂O₃) serves as a critical temperature requiring stringent control; temperatures above this threshold accelerate exothermic oxidation at Fe sites. The parent compound exhibits a prominent resistivity anomaly near 128 K, which is closely associated with spin-density-wave (SDW) instability. U doping effectively suppresses SDW instability and induces zero-resistance behavior in Gd_0.95U_0.05FeAsO. Hall effect measurements further confirm that U doping introduces electron-type charge carriers into the system.