Stability Study on Crystal Structure of (La_1-yNd_y)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.