The structure, composition, and thermoelectric properties of cobalt monosilicide obtained by crystallization from a supersaturated solution–melt in tin are studied. A technique for the synthesis and directional solidification of microcrystalline and bulk textured materials in a single technological cycle is developed.
High values of the thermoelectric figure of merit ( ZT = 1.5) in Mg_2Si–Mg_2Sn solid solutions are caused by a low thermal conductivity and a complex band structure, which is optimal at the ratio of solid-solution components of 40% Mg_2Si and 60% Mg_2Sn. However, the presence of magnesium stannide in a high concentration impairs the mechanical properties and chemical stability of the material limiting its application at high temperatures. Magnesium silicide has a higher stability but a lower figure of merit. The figure of merit is much lower in Mg_2Si-rich solid solutions and amounts to ZT ~ 1. The possibility of increasing ZT in the Mg_2Si_0.8Sn_0.2 solid solution with the additional inclusion of Mg_2Ge in small quantities is investigated here. Samples of Mg_2(Si_1 –_ x Ge_ x )_0.8Sn_0.2 ( x < 0.03) solid solution are prepared by hot pressing. The temperature dependences of the coefficients of the thermoelectric power, electrical conductivity, and thermal conductivity are measured in the range of 300–800 K. An increase in the thermoelectric figure of merit to ZT = 1.1 is shown at T = 800 K in the Mg_2Si_0.78Ge_0.02Sn_0.2〈Sb〉 solid solution.
Исследованы термоэлектрические свойства твердого раствора Mg2Ge0.3Sn0.7, легированного Ga и Li. Получены образцы с концентрацией дырок до 5·1020 см-3. Измерены температурные зависимости термоэдс, электропроводности и теплопроводности от комнатной температуры до 800 K. Наблюдается более высокая подвижность свободных носителей на образцах, легированных литием, чем в образцах с галлием. Максимальная безразмерная термоэлектрическая добротность на исследованных образцах составила 0.42 при 700 K. DOI: 10.21883/FTP.2017.08.44785.54
In this work, we study the properties of GeTe -based alloys, doped with bismuth, with partial substitution of lead for germanium: Ge0.86Pb0.1Bi0.04Te. The aim of the study is to explore the possibility of increasing the thermoelectric efficiency of a compound by combining optimal doping and isovalent substitution to improve the electronic properties with a simultaneous decrease of the lattice thermal conductivity. We studied alloy samples prepared in two different research laboratories using similar, but not completely identical procedures. It is shown that the electronic (thermoelectric power and electrical conductivity) properties of the samples of the two groups are in good agreement with each other. The properties of alloys depend on the thermal history of the samples due to the presence at temperatures of 600–800 K of a phase transition from a low-temperature rhombohedral to a high-temperature cubic structural modification. The thermoelectric figure of merit of alloys reaches a maximum value of 1.5 at a temperature of about 750 K.
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