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For decades, the bismuth telluride (Bi2Te3)-based materials have been well-established thermoelectric materials used in thermoelectric cooler, which crystalizes in a layered rhombohedral lattice and shows strong anisotropic transport properties. Herein, we demonstrate that the addition of Ga in Bi2Te3 reveals the changeover of conduction type with respect to the doping ratios, which can be further elaborated by the transition in phase regions. The 523K isothermal section of ternary Bi-Te-Ga, which is constructed by experiments, acts as a roadmap and provides adequate information for phase boundaries and alloying selections. As a consequence, the Bridgman-grown Ga-doped Bi2Te3 achieved a high zT of 1.5 at 300K, which is attributed to the enhanced power factor (=S2/ρ) and reduced electrical conductivity.
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