Bridgman Growth of Mg₂Sn_1–xBi_xSingle Crystals and Anisotropic Thermoelectric Properties

Abstract

Mg 2 X-based (X = Si, Ge, Sn) phases are promising for thermoelectric applications due to their nontoxicity, low cost, and high performance. Substantial experimental work has already been carried out based on the polycrystalline samples; however, studies on related single-crystal growth and corresponding properties are still very limited owing to the high volatility and reactivity of Mg, which makes it very challenging to obtain highquality single crystals with big sizes. In this report, for the first time, the Bridgman method was successfully applied in the single-crystal growth of the Bi-doped Mg 2 Sn materials. The crystals are of high quality and related anisotropic thermoelectric properties were systematically investigated. The Bi-doped Mg 2 Sn 0.99 Bi 0.01 single crystal exhibited a maximum zT value of 0.58 along the [111] orientation at 623 K, which is about 30 times that of the pristine Mg 2 Sn single crystal.

Mg-Defect Compensation to Realize High Performance at Room Temperature in Mg3Bi2-Based Thermoelectric Single Crystals

“…Thermoelectric materials can directly realize the energy conversion between electricity and heat and are promising in applications of recovering low-grade heat resources and improving the utilization efficiency of current fossil fuels. − The energy conversion efficiency of a thermoelectric material is evaluated through the dimensionless thermoelectric value zT , defined by zT = S 2 σT/ κ, where S is the Seebeck coefficient, σ is the electrical conductivity, κ is the thermal conductivity, and T is the absolute temperature. By a simple examination of the above equation, high-performance thermoelectric materials should possess high electrical conductivity and Seebeck coefficient and, meanwhile, very low thermal conductivity. − …”