Thermoelectric Properties of Ba1.9Ca2.4Mg9.7Si7: A New Silicide Zintl Phase with the Zr2Fe12P7 Structure Type

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• 作者：Kurt Silsby ; Fan Sui ; Xiaowei Ma ; Susan M. Kauzlarich ; Susan E. Latturner
• 刊名：Chemistry of Materials
• 出版年：2015
• 出版时间：October 13, 2015
• 年：2015
• 卷：27
• 期：19
• 页码：6708-6716
• 全文大小：523K
• ISSN：1520-5002

文摘

Ba_1.9Ca_2.4Mg_9.7Si₇ was grown as large crystals from the reaction of silicon with barium and calcium in Mg/Al flux. This compound is a charge-balanced Zintl phase with the Zr₂Fe₁₂P₇ structure type in hexagonal space group P6虆 (a = 11.196(2) 脜, c = 4.4595(9) 脜); barium occupies the Zr sites, the lighter alkaline earths (Mg, Ca) mix on the Fe sites, and silicon occupies the phosphorus sites. An isostructural germanide (Ba_1.2Sr_0.9Mg_11.9Ge₇, a = 11.064(1) 脜, c = 4.3709(6) 脜)) was similarly synthesized from reactions of germanium with barium and strontium in Mg/Al flux. Density of states calculations indicate these phases are semimetals, in agreement with their charge-balanced nature. Measurements of electrical resistivity, thermal conductivity, and Seebeck coefficient were carried out from 300鈥?000 K to investigate the thermoelectric properties of Ba_1.9Ca_2.4Mg_9.7Si₇. This compound is an n-type semimetal with low thermal conductivity (2 W/(m路K)), moderate Seebeck coefficient (鈭?00 渭V/K at 900 K), and a thermoelectric figure of merit ZT of 0.35 at 900 K.