Densifications and mechanical properties of single-phase Gd2Zr2O7 ceramic waste forms with improved TRPO waste load

A nitrate-citrate combustion method combined with microwave sintering was firstly employed for the rapid fabrication of the Gd2Zr2O7 matrix immobilizing various amounts of simulated nuclear wastes. Phase evolutions, microstructure changes, element distributions, densification processes and mechanical properties of the asprepared (1 - x)Gd2Zr2O7 center dot xTRPO (0.0 <= x <= 0.6) at various temperatures were investigated. Compared to the reported studies, we have increased the immobilization amount of simulated TRPO waste within a crystal structure from 45 to 60 wt%. T-d and T-g (the threshold temperatures to trigger accelerated densification and grain growth, respectively) were employed to divide the densification process into three stages. the mechanical properties and the densification stages of the (1 - x)Gd2Zr2O7 center dot xTRPO (0.0 <= x <= 0.6) ceramics sintered under microwave sintering at various temperatures were finally determined. Fine-grained (1 - x)Gd2Zr2O7 center dot xTRPO (0.0 <= x <= 0.6) ceramic waste forms with average grain size less than 200 nm and relative density higher than 90% can be obtained by microwave sintering at sintering temperature less than 1400 degrees C.