Higher valency ion substitution causing different fluorite-derived structures in CaZr1-xNdxTi2-xNbxO7 (0.05 <= x <= 1) solid solution

doi:10.1016/j.ceramint.2020.09.119

	Higher valency ion substitution causing different fluorite-derived structures in CaZr1-xNdxTi2-xNbxO7 (0.05 <= x <= 1) solid solution
	Ji, Shiyin 1,4,5,6; Liao, Chang-Zhong 3,5; Chen, Shuangqiang 4; Zhang, Kuibao 5; Shih, Kaimin 3; Chang, Chung-Kai 2; Sheu, Hwo-shuenn 2; Yan, Shan 4; Li, Yuhong 4; Wang, Zhiguang 1,6
刊名	CERAMICS INTERNATIONAL
	2021-01-15
卷号	47 期号:2 页码:2694-2704
关键词	Fluorite-derived structures Substitution mechanism Evolutions of crystal structure X-ray methods
ISSN号	0272-8842
DOI	10.1016/j.ceramint.2020.09.119
通讯作者	Liao, Chang-Zhong(liaocz29@connect.hku.hk) ; Li, Yuhong(Liyuhong@lzu.edu.cn)
英文摘要	Fluorite-derived A(2)B(2)O(7) and ABC(2)O(7) structures, i.e. pyrochlore and zirconolite, are promising ceramic matrices for high-level radioactive waste immobilization, especially for minor actinides. Though substitutions of low valent cations were reported by many studies, fewer researches were carried out on the incorporation of high valency elements on these fluorite-derived matrices. In this study, a series of CaZr1-xNdxTi2-xNbxO7 (x = 0.05-1.0) ceramics was investigated to unravel the effect of Nb5+ - one of the main impurities in natural zirconolite, on the evolutions of crystal structure, substitution mechanism and phase transformation. X-ray photoelectron spectroscopy was used to confirm the existence of Nb5+ in the samples. Fluorite-derived structures (zirconolite-2M, 3T, 4 M and pyrochlore) with increasing Nb5+ contents simultaneously appeared as single-phase or multi-phase assemblages in the matrices, revealed by the combination of synchrotron X-ray diffraction and scanning electron microscopy-energy dispersive x-ray spectroscopy. Almost single-phase zirconolite-2M and pyrochlore were observed only in the ranges of 0.05 <= x <= 0.1 and 0.5 <= x <= 0.9, respectively. Rietveld structural analysis of the zirconolite-2M phase showed that Nd3+ ions preferably occupied the Zr sites while Nb5+ ions substituted the Ti sites. This result is different from the mechanisms reported in the literature when lower valency (<=+3) was as charge compensator or there was no charge compensator in the REE doped zirconolite (REE = rare earth element). In the pyrochlore structure, the Ca2+, Nd3+ and Zr4+ ions occupied the A sublattice while Ti4+ and Nb5+ ions filled in the B sublattice, and there is charge compensation between A and B sublattices. The results in this study showed a different charge compensation mechanism of the fluorite-derived structures when higher valency elements incorporate into the lattice and will be very helpful for high-level radioactive waste immobilization.
资助项目	National Natural Science Foundation of China of China[41701560] ; National Natural Science Foundation of China of China[11775102] ; National Natural Science Foundation of China of China[11805088] ; Open Project of State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials[17kffk05] ; Fundamental Research Funds for the Central Universities (Lanzhou University)[lzujbky-2018-19]
WOS研究方向	Materials Science
语种	英语
出版者	ELSEVIER SCI LTD
WOS记录号	WOS:000598469300005
资助机构	National Natural Science Foundation of China of China ; Open Project of State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials ; Fundamental Research Funds for the Central Universities (Lanzhou University)
内容类型	期刊论文
源URL	[http://119.78.100.186/handle/113462/138486]
专题	中国科学院近代物理研究所
通讯作者	Liao, Chang-Zhong; Li, Yuhong
作者单位	1.Chinese Acad Sci, Inst Modern Phys, Lanzhou 730000, Peoples R China 2.Natl Synchrotron Radiat Res Ctr, Hsinchu Sci Pk, Hsinchu 30076, Taiwan 3.Univ Hong Kong, Dept Civil Engn, Hong Kong, Peoples R China 4.Lanzhou Univ, Sch Nucl Sci & Technol, Lanzhou 730000, Peoples R China 5.Southwest Univ Sci & Technol, State Key Lab Environm Friendly Energy Mat, Mianyang 621010, Sichuan, Peoples R China 6.Univ Chinese Acad Sci, Sch Nucl Sci & Technol, Beijing 100049, Peoples R China
推荐引用方式 GB/T 7714	Ji, Shiyin,Liao, Chang-Zhong,Chen, Shuangqiang,et al. Higher valency ion substitution causing different fluorite-derived structures in CaZr1-xNdxTi2-xNbxO7 (0.05 <= x <= 1) solid solution[J]. CERAMICS INTERNATIONAL,2021,47(2):2694-2704.
APA	Ji, Shiyin.,Liao, Chang-Zhong.,Chen, Shuangqiang.,Zhang, Kuibao.,Shih, Kaimin.,...&Wang, Zhiguang.(2021).Higher valency ion substitution causing different fluorite-derived structures in CaZr1-xNdxTi2-xNbxO7 (0.05 <= x <= 1) solid solution.CERAMICS INTERNATIONAL,47(2),2694-2704.
MLA	Ji, Shiyin,et al."Higher valency ion substitution causing different fluorite-derived structures in CaZr1-xNdxTi2-xNbxO7 (0.05 <= x <= 1) solid solution".CERAMICS INTERNATIONAL 47.2(2021):2694-2704.