Comparison Study on Crystalline Phases in Ce-bearing Titanate SYNROC Synthesized by Conventional and Spark Plasma Sintering

R. Nakazawa, S. Maruyama, R. Maki, M. Nakase

SYNROC is a promising waste form for immobilizing actinide (An)-bearing radioactive waste. This study examined the effect of spark plasma sintering (SPS) on the phase assemblage of An-bearing SYNROC by comparing  with  conventional  sintering  in air.  Using  Ce  as  a  surrogate  of  An,  CaTiO₃-CaZrTi₂O₇-CeO₂ SYNROC was sintered at 1773 K.  The  air-sintered sample contained zirconolite-2M and 4M polytypes, alongside  a  pyrochlore  phase,  whereas  SPS  yielded  only  perovskite  and  fluorite.  This  difference  is attributed  to the  reducing  environment  imposed  during SPS.  The effect  of  SPS  is  further  discussed  by comparing the results with previous SPS studies.

WM2025 Proceedings