Phase Characterization, Thermal Stability, High-Temperature Transport Properties, and Electronic Structure of Rare-Earth Zintl Phosphides Eu3M2P4 (M = Ga, In)

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• 作者：Tanghong Yi ; Gaigong Zhang ; Naohito Tsujii ; Jean-Pierre Fleurial ; Alex Zevalkink ; G. Jeffrey Snyder ; Niels Gr酶nbech-Jensen ; Susan M. Kauzlarich
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：April 1, 2013
• 年：2013
• 卷：52
• 期：7
• 页码：3787-3794
• 全文大小：489K
• 年卷期：v.52,no.7(April 1, 2013)
• ISSN：1520-510X

文摘

Two rare-earth-containing ternary phosphides, Eu₃Ga₂P₄ and Eu₃In₂P₄, were synthesized by a two-step solid-state method with stoichiometric amounts of the constitutional elements. Refinements of the powder X-ray diffraction are consistent with the reported single-crystal structure with space group C2/c for Eu₃Ga₂P₄ and Pnnm for Eu₃In₂P₄. Thermal gravimetry and differential scanning calorimetry (TG-DSC) measurements reveal high thermal stability up to 1273 K. Thermal diffusivity measurements from room temperature to 800 K demonstrate thermal conductivity as low as 0.6 W/m路K for both compounds. Seebeck coefficient measurements from room temperature to 800 K indicate that both compounds are small band gap semiconductors. Eu₃Ga₂P₄ shows p-type conductivity and Eu₃In₂P₄ p-type conductivity in the temperature range 300鈥?00 K and n-type conductivity above 700 K. Electronic structure calculations result in band gaps of 0.60 and 0.29 eV for Eu₃Ga₂P₄ and Eu₃In₂P₄, respectively. As expected for a valence precise Zintl phase, electrical resistivity is large, approximately 2600 and 560 m惟路cm for Eu₃Ga₂P₄ and Eu₃In₂P₄ at room temperature, respectively. Measurements of transport properties suggest that these Zintl phosphides have potential for being good high-temperature thermoelectric materials with optimization of the charge carrier concentration by appropriate extrinsic dopants.