Systematic studies of the fundamental chemistry of pyrochlore oxides: An2Zr2O7 [An = Pu, Am, Cm, Bk and Cf]

Our efforts to pursue the fundamental science of actinide pyrochlore oxides, An2Zr2O7, (An = plutonium through californium), are presented. We have addressed their structural and chemical behavior via X-ray diffraction, Raman spectroscopy and by considering the pseudo-oxidation potentials of the actinides. The structures, fundamental chemistry, ionic radii and the electronic configuration of the specific actinide involved in these oxide systems all have a significant impact on their science. We are also exploring a calculational approach based on valence-bond relationships to assess the position of the oxygen atoms located at the general crystallographic position. The oxygen position is important regarding the chemical behavior and thermal stability of these materials. Also considered is the structural stability of the materials regarding self-irradiation, and with some compounds, their resistance towards oxidation. These aspects will be discussed using a systematic evaluation of the five-actinide systems together with comparable lanthanide systems studied. © 2002 Atomic Energy Society of Japan.