|
|||||
|
|
Synthesis of (Ca,Ce,Ce)2Ti2O7: a pyrochlore with mixed-valence cerium |
|
| Authors: | Laurence AJ Garvie Huifang Xu Yifeng Wang Robert L Putnam |
| Institution: | a Department of Geological Sciences, Arizona State University, Tempe, AZ 85287-1404, USA b Transmission Electron Microscopy Laboratory, Department of Earth and Planetary Sciences, The University of New Mexico, Albuquerque, NM 87131, USA c Sandia National Laboratories, Albuquerque, NM 87185, USA d Los Alamos National Laboratory, Los Alamos, NM 87545, USA |
| Abstract: | Pyrochlore with mixed-valence Ce was synthesized by firing and annealing Ce(NO3)4, TiO2, and Ca(OH)2 with a stoichiometry of CaCeTi2O7 at 1300 °C. The product contains Ce-pyrochlore, Ce-rich perovskite, CeO2 (cerianite), and minor CaO. Electron energy-loss spectroscopy (EELS) revealed both Ce4+ and Ce3+ in the Ce-pyrochlore with a Ce4+ to total Ce (Ce4+/ΣCe) of 0.80 giving  . Cerium in the perovskite and cerianite is dominated by Ce3+ and Ce4+, respectively. High-resolution transmission electron microscope (HRTEM) images show that the boundary between Ce-pyrochlore and Ce-rich perovskite is semi-coherently bonded. The orientational relationship between the neighboring Ce-pyrochlore and Ce-rich perovskite is not random. Ce-pyrochlore (CaCeTi2O7) is a chemical analogue for CaPuTi2O7, which is a proposed ceramic waste form for deposition of excess weapons-usable Pu in geological repositories. It is postulated, based on the presence of Ce3+ in the Ce-pyrochlore, that neutron poisons such as Gd can be incorporated into the CaPuTi2O7 phase. |
| Keywords: | A Ceramics B Chemical synthesis C Electron energy loss spectroscopy (EELS) C Electron microscopy |
| 本文献已被 ScienceDirect 等数据库收录！ | |