Fabrication and phase transition of Gd2Zr2O7 ceramics immobilized various simulated radionuclides

Abstract

To investigate the feasibility of Gd2Zr2O7 used for disposal waste of multi-nuclides with multi-valence, simulated trialkyl phosphine oxides (TRPO) waste was chosen to research the fabrication method and phase evolution. A series of (Gd,A)2(Zr,B)2O7 ceramics were successfully fabricated through a solid-state reaction sintering at 1500°C for 72h. XRD studies reveal that the compositions containing up to 35wt.% simulated TRPO waste exhibit a single pyrochlore structure, while the doping content varies from 35 to 65wt.%, the samples adopt a single defect fluorite structure. In the discussed range, the lattice parameter decreases with the increased doping content, and the rA/rB ratio decreases from 1.43 to 1.27, while the degree order increases in turn. Furthermore, the densification and grain growth in pyrochlore structure are promoted by an enhanced doping content.