Rapid Microwave Preparation of Thermoelectric TiNiSn and TiCoSb Half-Heusler Compounds

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• 作者：Christina S. Birkel ; Wolfgang G. Zeier ; Jason E. Douglas ; Bethany R. Lettiere ; Carolyn E. Mills ; Gareth Seward ; Alexander Birkel ; Matthew L. Snedaker ; Yichi Zhang ; G. Jeffrey Snyder ; Tresa M. Pollock ; Ram Seshadri ; Galen D. Stucky
• 刊名：Chemistry of Materials
• 出版年：2012
• 出版时间：July 10, 2012
• 年：2012
• 卷：24
• 期：13
• 页码：2558-2565
• 全文大小：454K
• 年卷期：v.24,no.13(July 10, 2012)
• ISSN：1520-5002

文摘

The 18-electron ternary intermetallic systems TiNiSn and TiCoSb are promising for applications as high-temperature thermoelectrics and comprise earth-abundant, and relatively nontoxic elements. Heusler and half-Heusler compounds are usually prepared by conventional solid state methods involving arc-melting and annealing at high temperatures for an extended period of time. Here, we report an energy-saving preparation route using a domestic microwave oven, reducing the reaction time significantly from more than a week to one minute. A microwave susceptor material rapidly heats the elemental starting materials inside an evacuated quartz tube resulting in near single phase compounds. The initial preparation is followed by a densification step involving hot-pressing, which reduces the amount of secondary phases, as verified by synchrotron X-ray diffraction, leading to the desired half-Heusler compounds, demonstrating that hot-pressing should be treated as part of the preparative process. For TiNiSn, high thermoelectric power factors of 2 mW/mK² at temperatures in the 700 to 800 K range, and zT values of around 0.4 are found, with the microwave-prepared sample displaying somewhat superior properties to conventionally prepared half-Heuslers due to lower thermal conductivity. The TiCoSb sample shows a lower thermoelectric figure of merit when prepared using microwave methods because of a metallic second phase.

Keywords:

ler&qsSearchArea=searchText">Heusler; llics&qsSearchArea=searchText">intermetallics; microwave synthesis; lectrics&qsSearchArea=searchText">thermoelectrics; TiNiSn; TiCoSb