Synthesis of (Ca,Ce3+,Ce4+)2Ti2O7:: a pyrochlore with mixed-valence cerium

被引：28

作者：

Garvie, LAJ ^{[1
]}

Xu, HF

Wang, YF

Putnam, RL

机构：

[1] Arizona State Univ, Dept Geol Sci, Tempe, AZ 85287 USA

[2] Univ New Mexico, Dept Earth & Planetary Sci, Transmiss Elect Microscopy Lab, Albuquerque, NM 87131 USA

[3] Sandia Natl Labs, Albuquerque, NM 87185 USA

[4] Los Alamos Natl Lab, Los Alamos, NM 87545 USA

来源：

JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS | 2005年 / 66卷 / 05期

基金：

美国国家科学基金会;

关键词：

ceramics; chemical synthesis; electron energy loss spectroscopy (EELS); electron microscopy;

D O I：

10.1016/j.jpcs.2004.10.012

中图分类号：

O6 [化学];

学科分类号：

0703 ;

摘要：

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 degrees 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+/Sigma Ce) of 0.80 giving (Ca0.87Ce0.213+ Ce-0.86(4+))Ti2.05O7. Cerium in the perovskite and cerianite is dominated by Ce3+ and Ce4+, respectively. High-resolution transmission electron microscope (FIRTEM) images show that the boundary between Ce-pyrochlore and Ce-rich perovskite is semicoherently bonded. The orientational relationship between the neighboring Ce-pyrochlore and Cc-rich perovskite is not random. Cepyrochlore (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. (c) 2005 Elsevier Ltd. All rights reserved.

引用

页码：902 / 905

页数：4

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