High-Quality Large Single-Crystal Growth and the Thermoelectric Properties of CsBi ₄ Te ₆

The CsBi₄Te₆ crystal is the most promising <i>p</i>-type thermoelectric material below room temperature due to its strongly anisotropic electrical transport and low thermal conductivity. In this work, the largest centimeter-sized single crystal (ø20 mm × 25 mm) of CsBi₄Te₆ with high quality, was successfully grown using the Bridgman method by precisely adjusting the growth temperature. This solution can effectively prevent the volatilization of Cs and avoid corrosion of the crucible. A peak figure of merit (<i>zT</i>) of 0.07 at 323 K was achieved based on the single crystal along the <i>b</i>-axis. Besides, the Vickers hardness (0.75 GPa) and the Young's modulus (23 GPa) of CsBi₄Te₆ were also investigated for the first time. The high-quality single-crystal growth in this study sheds light on the further exploration of the low-temperature thermoelectric material CsBi₄Te₆, which benefits the development of ultralow-temperature thermoelectric cooling technology.