Phase and microstructure evolution of 0.2Zr1-xCexO2/Zr1-yCeySiO4 (0 ≤ x + y ≤ 1) ceramics designed to immobilize tetravalent actinides

Zircon is important ceramic used widely due to its excellent properties, in particular for nuclear waste immobilization . However, it is difficult to obtain mono-phase zircon with high yield, usually result in double-phase ZrO 2 /ZrSiO 4 ceramics. Herein, Ce-doped double-phase 0.2Zr 1- x Ce x O 2 /Zr 1- y Ce y SiO 4 (0 ≤  x  +  y  ≤ 1) ceramics were fabricated and their phase and microstructure evolution were studied. The results demonstrated that Ce content has great influence on the phase composition and microstructure. The ceramics with 0 ≤ x  +  y  < 0.1 are tetragonal-ZrSiO 4 , monoclinic-ZrO 2 and tetragonal-ZrO 2 phases, with 0.1 ≤ x  +  y  ≤ 0.3 are tetragonal-ZrSiO 4 , monoclinic-ZrO 2 , tetragonal-ZrO 2 and cubic-ZrO 2 phases, with 0.3 < x  +  y  ≤ 0.6 are tetragonal-ZrSiO 4 , tetragonal-ZrO 2 and cubic-ZrO 2 phases, and with 0.6 < x  +  y  ≤ 1 are cubic-ZrO 2 and Ce 2 Si 2 O 7 phases. With increasing Ce-doping content, the ZrSiO 4 retained the tetragonal phase, while ZrO 2 transformed from monoclinic to stable cubic phase. Furthermore, lattice parameters , grain size and compactness increased with increasing Ce content.