Interfacial Cation Mixing and Microstructural Changes in Bilayer GTO/GZO Thin Films After Irradiation.

In many applications involving functional oxides, composite structures consisting of multiple oxides and interfaces between the two are of particular interest, as they provide enhanced properties over the individual phases. Often, materials intended for radioisotope immobilization are composite structures, consisting of multiple chemistries and structures. In this work, two pyrochlore materials, Gd 2 Zr 2 O 7 (GZO) and Gd 2 Ti 2 O 7 (GTO) are interfaced in a bilayer structure and irradiated to test the composite's capacity to accommodate lattice point defects and the potential for cation transport across the interface. Using x-ray energy dispersive spectroscopy after the pristine bilayer was irradiated to damage levels of 0.2–0.8 dpa using a 12 MeV Cu 4 + ion beam, significant cation intermixing was observed by the highest dose. While, as might be expected, the bulk of the GTO layer easily amorphized, surprisingly, the GZO layer also amorphized with arelatively small dose. More interestingly, the structure maintained a crystalline layer at the original interface between the two pyrochlores, even though the interface moved significantly during the irradiation. These results are explained through a physical model for ballistic mixing in pyrochlore. These results highlight the complex structural response of oxide heterostructures under extreme conditions. [ABSTRACT FROM AUTHOR]