| Thermoelectric materials, which can realize transformation between the electricalenergy and the heat energy directly, are of great advantage for some special utilities. Theyhave been widely used in aerospace, defense industry, medical treatment, electronictechnology, and many other fields. However, most Bi2Te3-based bulks are prepared byzone melting process which is high energy consumption, high cost and long productionperiod. So it’s very urgent and necessary to improve a traditional process forthermoelectric materials. Based on a detailed review on the research status and developingtrend of thermoelectric materials, the research topic of this thesis is focused on exploringthe vacuum melting process of Bi2Te3-based bulk thermoelectric materials.In this paper, p-type （Bi0.26Sb0.74）2Te3+3%Te thermoelctric materials were preparedby a traditional vacuum melting method. The phase, microstructure and chemicalcomposition of the ingots are characterized by XRD, SEM, EDAX, respectively. Thethermoelectric properties of ingots, including Seebeck coefficient, electrical resistivity andthermal conductivity, are also measured and analysised. Effect of processing parameters ofvacuum melting on thermoelctric properties was explored, and the main results wereobtained as follows:With increase of cooling rates, the amount and size of Te-rich phase increases, theelectrical resistivity and the Seebeck coefficient both decreases. While thermalconductivities of all ingots are about1.0W/mK. The p-type（Bi0.26Sb0.74）2Te3+3%Te ingot,which was prepared at a cooling rate of4K/min, achieves a maximum ZT of1.12（T=298K）.Melting for a proper duration is good for thermoelectric properties of the ingots. Incomparison with the1h melting sample, the thermoelectric properties of the3h melting sample were greatly improved. Stirring the alloy liquid during melting can get rid of gasabsorption in the inner surface of the mold, thus the appearance qulity of the ingots can begreatly improved. |
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