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Issue 7, 2017
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Defect control in Ca1−δCeδAg1−δSb (δ ≈ 0.15) through Nb doping

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Zintl phases with the nominal compositions Ca1−δREδAg1−δSb (RE = La, Ce, Pr, Nd, Sm; δ ≈ 0.15) are interesting due to their unique crystal structures and potential as high temperature thermoelectrics. Their structures generally feature the LiGaGe type structure with substantial vacancies on the Ag sites. The formation of such defects can be explained by the electronic effects, with which 18 electrons are required to stabilize the CaAgSb Zintl system. Since the substitution of Ca2+ with RE3+ will lead to electron excess, the formation of Ag defects will be an intrinsic character of such compounds to maintain their electron precise nature. In this work, the material Ca0.85Ce0.15Ag0.85Sb was selected for a detailed study on defect chemistry. In order to better understand the mechanism related to the defect formation and control in this system, we conducted a series of experiments aimed at controlling the point defects in Ca0.85Ce0.15Ag0.85Sb. This strategy was realized by intentionally doping Nb, which resulted in the discovery of a series of low defect density materials Ca0.725+xNb0.1−xCe0.15AgSb (0 ≤ x ≤ 0.05). In this work, an interesting defect controlling strategy on Zintl phases was demonstrated, which suggested the high flexibility of Ca1−δREδAg1−δSb in the optimization of thermoelectric properties.

Graphical abstract: Defect control in Ca1−δCeδAg1−δSb (δ ≈ 0.15) through Nb doping

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Publication details

The article was received on 01 Mar 2017, accepted on 24 Apr 2017 and first published on 02 May 2017

Article type: Research Article
DOI: 10.1039/C7QI00121E
Citation: Inorg. Chem. Front., 2017,4, 1113-1119
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    Defect control in Ca1−δCeδAg1−δSb (δ ≈ 0.15) through Nb doping

    X. Li, J. Yu, Y. Liu, Z. Wu, J. Guo, T. Zhu, X. Zhao, X. Tao and S. Xia, Inorg. Chem. Front., 2017, 4, 1113
    DOI: 10.1039/C7QI00121E

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