Effect of improved trialkyl phosphine oxides waste content on phase composition and density of spark plasma sintered Gd 2 Zr 2 O 7 ceramics

Abstract

As a rapid sintering method, spark plasma sintering (SPS) process has been widely applied to immobilize nuclear waste. In this work, trialkyl phosphine oxides (TRPO) were immobilized by the mixture of Gd2O3 and ZrO2 with SPS proceedings at 1650°C in 3 minutes. X-ray diffraction results present that the solid solubility is 10 to 20 wt% and all the sintered samples show a fluorite structure. Raman spectroscopy results show that the order degree of structure decreases as waste content increases. The lattice parameters decrease with the increasing doped waste content indicating the success of waste immobilization. Densities decrease for the sample with higher waste content which mainly caused by the existence of pores. Scanning electron microscope-energy dispersive X-ray spectroscopy and backscattered electron results perform the microstructure of the sintered sample. Furthermore, the leaching test shows that the sample has a considerable chemical stability. This study confirmed the possibility of rapid consolidation of Gd2Zr2O7 bulk, dense ceramic with up to 10 ~ 20 wt% of immobilized TRPO waste. Highlights Multi-nuclides waste was rapidly immobilized by Gd2Zr2O7 via SPS process. Phase transition happened with enhanced doping content. Density results decreased with the higher waste content. The order degree of structure decreased as waste content increased. The sintered matrix represented considerable chemical stability.