Robert Aughterson

The development of radionuclide-containing matrixmaterials, for ceramic-based high-level nuclear wasteforms or neutron absorbent fuel components, requires both a robust matrix material and a neutron absorbent isotope. Here, we fabricated a series of compounds Gd2(Ti1-xZrx)O5 (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5) using the conventional oxide route of mixing oxide precursors, pressing, and sintering in air to various maximum temperatures. Crystal structure refinement of x-ray diffraction data indicates zirconium-containing compounds to be of the defect-fluorite form, Fm-3m space group. There is sequential decrease in the cell parameter with increasing titanium content from Gd2Ti0.5Zr0.5O5, a = 5.27795 (4) Å to Gd2Ti0.8Zr0.2O5, a = 5.2475 (4) Å. However, electron diffraction analysis highlights greater crystal structure complexity, including a 4× fluorite superstructure and additional diffuse diffraction features. The Argonne National Laboratory IVEM-Tandem in situ irradiation facility has been utilized to characterize the 1 MeV krypton irradiation response for this system of compounds. The addition of zirconium has improved the radiation response, increasing the fluence required for amorphization and lowering the temperature for maintaining the crystalline structure. For the Gd2Ti0.8Zr0.2O5, a critical temperature of 936 K was found, while for Gd2Ti0.5Zr0.5O5, the Tc was 565 K.