Self-propagating high-temperature synthesis of ZrO ₂ incorporated Gd ₂Ti ₂O ₇ pyrochlore

Abstract

In this research, Zr-doped Gd ₂Ti ₂O ₇ pyrochlores, with the composition of Gd ₂(Ti _{1- x} Zr _x ) ₂O ₇, were firstly synthesized by self-propagating high-temperature synthesis plus quick pressing (SHS/QP) using CuO as the oxidant and Ti as the reductant. To improve the radiation resistance of titanate–pyrochlore, up to 35 at% Zr was incorporated to substitute the Ti site of Gd ₂Ti ₂O ₇ pyrochlore (Gd ₂(Ti _0.75Zr _0.35) ₂O ₇). XRD and SEM microstructural characterizations showed the formation of a composite ceramic with the major pyrochlore phase and the minor Cu phase. The generated temperature of samples decreased from 1702 to 1011 ℃ with increasing Zr content. The effects of sintering temperature and pressure time on phase composition and microstructure were systematically studied. Besides, the influence of thermal transmission on the whole combustion process was also explored. The pyrochlore-based waste form possessed high bulk density of 6.25 g/cm ³ and Vickers hardness of 10.81 GPa. The MCC-1 leaching test showed the normalized elemental leaching rates (42 d) of Cu, Gd, and Zr are 1.27×10 ^-2, 1.33×10 ^-3, and 8.44×10 ^-7 g·m ^-2·d ^-1, respectively.