Stability and properties of the friendly environmental Zintl phases: Ca₃Si₄ and Ca₁₄Si₁₉

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• 作者：Adrien Moll^a ; Romain Viennois^a ; Patrick Hermet^a ; Abel Haidoux^a ; Jean-Louis Bantignies^b ; Micka&euml ; l Beaudhuin^a ; ^{mickael.beaudhuin@umontpellier.fr}
• 关键词：Semiconductors ; Stability ; Raman spectroscopy ; Ab initio calculation ; Phase diagram
• 刊名：Acta Materialia
• 出版年：2017
• 出版时间：15 February 2017
• 年：2017
• 卷：125
• 期：Complete
• 页码：490-497
• 全文大小：2367 K
• 卷排序：125

文摘

We report the synthesis, stability, lattice dynamics and electronic properties of two Zintl phases, Ca3Si4 and Ca14Si19, made of abundant and non-toxic elements in order to evaluate their potential applications. A simple two-step synthesis approach has permitted (i) to reach good purity of these two silicide phases and (ii) to reinvestigate their coexistence domain which permits to lift the uncertainty of the phase diagram within the 50–70 at. % Si region. Our first-principles calculations are able to well describe for the first time both the experimental vibrational properties studied by Raman spectroscopy and the energy bandgap determined by diffuse reflectance experiments. The two compounds are narrow-gap intrinsic semiconductors with indirect energy bandgaps about 0.56 eV and smaller than 0.1 eV for Ca3Si4 and Ca14Si19, respectively. Their Seebeck coefficient has been measured to 42 μV/K (Ca3Si4) and −183 μV/K (Ca14Si19) at room temperature which suggests their p- and n-type semiconducting behavior, respectively.