烧绿石(La1-yNdy)2Zr2O7模拟固化241Am的晶体结构稳定性研究

为研究²⁴¹Am在La₂Zr₂O₇烧绿石中的固化行为及其对烧绿石晶体结构稳定性的影响，实验选用Nd作为²⁴¹Am的模拟物，采用Sol-喷雾热解法合成了(La_1-yNd_y)₂Zr₂O₇（0.0≤y≤1.0）系列样品，并借助X射线衍射和振动光谱手段对样品的晶体结构稳定性进行了研究。实验结果表明：随着Nd掺杂量的增加，O48f位置参数x_48f和I₍₁₁₁₎ /I₍₂₂₂₎均呈规律性增大，Raman谱逐渐展宽，IR谱发生蓝移，所有结果均证实用Nd不断替换La将导致烧绿石晶体结构有序化程度逐渐降低。另外，实验发现掺杂量y≈0.8是烧绿石晶体结构发生几何相变的逾渗阈值，超过该阈值有序的烧绿石结构将发生突变进而加速向无序萤石结构转变，该实验结果可为(La_1-yAm_y)2Zr2O7固溶体的结构稳定性研究提供参考。

Stability Study on Crystal Structure of(La1-yNdy)2Zr2O7 Pyrochlore Simulated Immobilizing 241Am

In order to study immobilization behavior and the effect of ²⁴¹Am to crystal structure stability of pyrochlore, Nd was used as surrogate element for ²⁴¹Am. A series of (La_1-yNd_y)₂Zr₂O₇(0.0≤y≤1.0) samples were synthesized by Sol-spray pyrolysis method. The crystal structure stability was characterized by powder X-ray diffraction and vibration spectrum. The results indicate that with the increase of Nd concentration in (La_1-yNd_y)₂Zr₂O₇, the values of the x48f parameter of the O48f and I₍₁₁₁₎/I₍₂₂₂₎ increase regularly and Raman spectrum gradually broadens as well as IR spectrum happens blue shift, which proves that the ordering degree of crystal structure in  (La_1-yNd_y)₂Zr₂O₇ gradually reduces with Nd constantly replacing La. In addition, experiments find that y≈0.8 is of the percolation threshold value to pyrochlore happening geometric phase transition, and order pyrochlore structure will have a sudden change and quickly transforms to the disordered fluorite structure with more than the threshold value. The experiment results can provide a reference to (La_1-yAm_y)₂Zr₂O₇ solid solution  structure stability.