合成与铀烧绿石型 beta 钙钛矿 [(Ca,U)(Ti,Nb,Ta))₂O₇] 的结构表征。

Synthesis and characterisation of the uranium pyrochlore betafite [(Ca,U)₂(Ti,Nb,Ta)₂O₇].

机构信息

Centre for Advanced Materials and Industrial Chemistry, School of Applied Sciences RMIT University, GPO Box 2476, Melbourne, Vic 3001, Australia.

CSIRO Process Science and Engineering, Bayview Avenue Clayton, Victoria 3168, Australia.

出版信息

J Hazard Mater. 2014 Sep 15;280:478-86. doi: 10.1016/j.jhazmat.2014.07.062. Epub 2014 Aug 7.

DOI:10.1016/j.jhazmat.2014.07.062

PMID:25199504

Abstract

Betafite of composition [(Ca,U)2(Ti,Nb,Ta)2O7] was prepared via a solid state synthesis route. The synthesis was shown to be sensitive to initial reactant ratios, the atmosphere used (oxidising, neutral, reducing) and time. The optimum conditions for the synthesis of betafite were found to be heating the reactants required at 1150°C for 48 h under an inert gas atmosphere. XRD characterisation revealed that the synthesised betafite contained minor impurities. EPMA analysis of a sectioned surface showed very small regions of Ca-free betafite on grain boundaries as well as minor rutile impurities. Some heterogeneity between the Nb:Ta ratio was observed by quantitative EPMA but was generally within the nomenclature requirements stated for betafite. SEM analysis revealed the synthesised betafite was comprised mostly of hexaoctohedral crystals of ∼ 3 μm in diameter. XPS analysis of the sample showed that the uranium in the synthesised betafite was predominately present in the U(5+) oxidation state. A minor amount of U(6+) was also detected which was possibly due to surface oxidation.

摘要

β-钙钛矿[(Ca,U)2(Ti,Nb,Ta)2O7]通过固态合成法制备。结果表明，该合成对初始反应物比例、使用的气氛（氧化、中性、还原）和时间敏感。β-钙钛矿合成的最佳条件为在惰性气体气氛下，将反应物加热至 1150°C 并持续 48 小时。XRD 特征分析表明，所合成的β-钙钛矿含有少量杂质。对截面的 EPMA 分析表明，在晶界处存在少量无钙β-钙钛矿以及少量金红石杂质。通过定量 EPMA 观察到 Nb:Ta 比值存在一定的不均匀性，但总体上符合β-钙钛矿的命名要求。SEM 分析表明，所合成的β-钙钛矿主要由直径约为 3μm 的六八面体晶体组成。XPS 分析表明，所合成的β-钙钛矿中铀主要以 U(5+)氧化态存在。还检测到少量的 U(6+)，这可能是由于表面氧化所致。