Self-propagating high-temperature synthesis of ZrO2 incorporated Gd2Ti2O7 pyrochlore

Abstract

In this research, Zr-doped Gd 2 Ti 2 O 7 pyrochlores, with the composition of Gd 2 (Ti 1x Zr x) 2 O 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 2 Ti 2 O 7 pyrochlore (Gd 2 (Ti 0.75 Zr 0.35) 2 O 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.

Synchrotron x‐ray spectroscopy investigation of the Ca1−xLnxZrTi2−x(Al, Fe)xO7 zirconolite ceramics (Ln = La, Nd, Gd, Ho, Yb)

“…After decades of research, the SYNROC, glass-ceramic, and single-phase ceramic minerals (zirconolite, pyrochlore, monazite and so on) have been employed to immobilize HLW which contains considerable minor actinides due to their advantages in physicalchemical properties and high solubility of actinides. 1,3,[6][7][8][9][10][11][12][13][14][15][16] As one of the advanced ceramic waste forms, zirconolite has excellent properties in radiation resistance, mechanical stability, high waste loading, high thermal conductivity, and low leach rate and has been considered to be a potential candidate for the disposal of HLW. 9 As a promising matrix of HLW ceramic waste forms, zirconolite has several polymorphs.…”

Corrosion resistance of non-stoichiometric gadolinium zirconate fabricated by laser-enhanced chemical vapor deposition

“…Gadolinium zirconate (GZ) is a promising candidate of TBCs for the next-generation turbine engines [10][11][12][13]. The crystal structure of GZ can be described as a Zr 4 O 12 framework with an imbricated Gd 4 O 2 polyhedron inside [14][15][16].…”

Self-Propagating Synthesis and Characterization Studies of Gd-Bearing Hf-Zirconolite Ceramic Waste Forms

“…Because of its special advantages [35], SHS technique has been considered as a candidate approach for environment protection, such as stabilization of radioactive and toxic wastes. In recent years, we have explored the rapid synthesis of zirconolite and pyrochlore based waste forms using SHS [36,37,38,39,40,41]. Quick pressing (QP) was also introduced to obtain highly densified samples.…”