Synthesis of (Ca,Ce3+,Ce4+)2Ti 2O7: A pyrochlore with mixed-valence cerium

Laurence Garvie, Huifang Xu, Yifeng Wang, Robert L. Putnam

Research output: Contribution to journalArticle

27 Scopus citations

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 Ce 4+ and Ce3+ in the Ce-pyrochlore with a Ce4+ to total Ce (Ce4+/ΣCe) of 0.80 giving (Ca0.87Ce0.213+Ce0.864+) Ti2.05O7. 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 CaPuTi2O 7 phase.

Original languageEnglish (US)
Pages (from-to)902-905
Number of pages4
JournalJournal of Physics and Chemistry of Solids
Volume66
Issue number5
DOIs
StatePublished - May 1 2005

Keywords

  • A. Ceramics
  • B. Chemical synthesis
  • C. Electron energy loss spectroscopy (EELS)
  • C. Electron microscopy

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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