Effect of Ce4+-substitution at A and B sites of Nd2Zr2O7: A study for plutonium incorporation in pyrochlores

Controllable sites and high-capacity immobilization of uranium in Nd2Zr2O7 pyrochlore

“…Peaks a and b/c correspond to the electronic transition from the 1s to 4d orbital and the dipole-allowed transition from the 1s to 5p orbital, respectively (Komyoji et al, 1992;Popov et al, 2019). These features of all samples are close to those in the pyrochlore phase rather than in the defect-fluorite phase (Nandi et al, 2020). In Zr K-edge XANES, the pre-edge feature a for all samples is significant, which indicates tetrahedral distortion of the ZrO 6 coordination polyhedron .…”

“…A noticeable change in the coordination number (CN) is observed for Zr-O 48f bonds during uranium doping. Compared with that in NZO, the CN values of Zr-O increased slightly in the AÀ 0.1 and B À 0.1 samples, which may be caused by the introduction of anions to maintain charge balance and preferentially fill the unoccupied 8a site in the pyrochlore structure (Hess et al, 2002;Na ¨stren et al, 2009). Since Zr is located at the 16c site (adjacent to the 8a site), the addition of Zr-O CN has little effect on the polyhedral structure of Zr-O 48f .…”

“…Among them, O 48f has special properties concerning the adjustment of oxygen disorder and structural distortion in pyrochlore (Hagiwara et al, 2019;Martin et al, 2009). Previous studies pointed out that the introduction of high-valent ions will cause the 8a oxygen vacancies to be partially filled and cause the anion disorder of Gd 2 Zr x Ti 2-x O 7+ pyrochlore (Na ¨stren et al, 2009). In the Nd L 3 -edge XANES, the strong white line originates from a dipole-allowed transition from core level 2p to 5d, and the spectral profile is related to the unoccupied Nd 5d states (Rao et al, 1983).…”

Radiation response of Y3Al5O12 and Nd3+–Y3Al5O12 to Swift heavy ions: insight into structural damage and defect dynamics

“…The effect of fission fragments on materials may be simulated by employing high energy heavy ion beams (swift heavy ions; SHI) from accelerators. 7 Various ceramic matrices have been researched over the last few years to assess their suitability for MA transmutation, such as stabilized cubic zirconia, 5,[8][9][10][11][12][13] pyrochlores (A 2 B 2 O 7 ), 14 carbides, metals, ceramic composites, etc. Y 3 Al 5 O 12 (YAG) garnet has also been proposed as one of the inert matrices.…”

“…Various ceramic matrices have been researched over the last few years to assess their suitability for MA transmutation, such as stabilized cubic zirconia, 5,8–13 pyrochlores (A 2 B 2 O 7 ), 14 carbides, metals, ceramic composites, etc. Y 3 Al 5 O 12 (YAG) garnet has also been proposed as one of the inert matrices.…”