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

Abstract

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 ZrO2/ZrSiO4 ceramics. Herein, Ce-doped double-phase 0.2Zr1-xCexO2/Zr1-yCeySiO4 (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-ZrSiO4, monoclinic-ZrO2 and tetragonal-ZrO2 phases, with 0.1 ≤ x + y ≤ 0.3 are tetragonal-ZrSiO4, monoclinic-ZrO2, tetragonal-ZrO2 and cubic-ZrO2 phases, with 0.3 <x + y ≤ 0.6 are tetragonal-ZrSiO4, tetragonal-ZrO2 and cubic-ZrO2 phases, and with 0.6 <x + y ≤ 1 are cubic-ZrO2 and Ce2Si2O7 phases. With increasing Ce-doping content, the ZrSiO4 retained the tetragonal phase, while ZrO2 transformed from monoclinic to stable cubic phase. Furthermore, lattice parameters, grain size and compactness increased with increasing Ce content.