Development of EuTiNbO₆ Euxenite Glass/Ceramic Composites as Potential Wasteforms For Immobilisation of Minor Actinide Wastes

The long-term immobilisation of actinide-rich radioactive wastes poses a major technical challenge. The present work explores euxenite glass/ceramic composites (GCCs) as potential wasteforms for minor actinides and lanthanide fission products. The aim was to generate dense dispersions of euxenite (EuTiNbO₆) stabilised in glass (NaAl_0.5B_0.5Si₃O₈). Sintering parameters were varied by temperature (1100°–1300°C), time (3–24 h), cooling rate (quenching, 5°–20 °C/min), and glass content (10–50 wt%). A fifth parameter involved adding excess oxides to suppress Ti and/or Nb leaching from euxenite by a reverse chemical gradient. The effects of these variables on structures, compositions, microstructures, phase assemblages, and densities were investigated. Higher temperatures promoted secondary-phase (EuNbO₄, TiO₂) formation, while longer sintering time promoted grain growth. Quenching suppressed secondary phases and increased glass content reduced porosity. Excess oxide addition revealed that Ti leaching initiates euxenite destabilisation. The results highlight the flexibility of these GCCs for immobilising minor actinide wastes.