Bi2Te3ySey

Bi2Te3ySey is an alloy of bismuth, tellurium, and selenium forming a solid solution that modifies the electronic band structure of the classic thermoelectric material Bi2Te3. The variable y in the formula denotes the fraction of tellurium atoms replaced by selenium, typically ranging from 0 to 1. The substitution introduces lattice strain and disorder, which reduces lattice thermal conductivity while preserving high carrier mobility. Because the thermoelectric figure of merit, ZT = S²σT/κ, is sensitive to both electrical and thermal transport, Bi2Te3ySey alloys reach peak ZT values near y ≈ 0.4–0.5 at room temperature. Synthesis methods include vacuum melting, mechanical alloying, and sol–gel processes, followed by hot‑pressing or spark plasma sintering to achieve dense bulk samples.

In terms of properties, the Seebeck coefficient of Bi2Te3ySey remains comparable to pure Bi2Te3, but the electrical conductivity shows a modest decrease with increasing selenium content, which balances the decrease in thermal conductivity. The alloy shows excellent stability in vacuum and inert atmospheres; however, exposure to moisture can lead to surface oxidation. Commercially, Bi2Te3ySey is used in small cooling devices, thermoelectric generators for automotive waste‑heat recovery, and in research for power conversion at low temperatures. Future studies focus on nanostructuring, alloying with other elements, and optimizing doping levels to further enhance performance.