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<p>Increasing the Te content in stoichiometric Bi<sub>0.5</sub>Sb<sub>1.5</sub>Te<sub>3</sub> facilitates effective control over the anti-site defects and nanostructure; however, arresting excess Te in the host matrix is challenging. Herein, we report the success of a saturation-annealing treatment in a vacuum, followed by air-quenching as a promising approach for synthesizing high figure-of-merit (<i>zT</i>) Bi<sub>0.5</sub>Sb<sub>1.5</sub>Te<sub>3</sub>+xTe (x = 0, 2, 5 and 10 wt%) materials. A remarkably high-power factor (<i>α</i><sup><i>2</i></sup><i>σ</i> ~ 6 mW at 300&#xa0;K) is achieved in <i>p</i>-type Bi<sub>0.5</sub>Sb<sub>1.5</sub>Te<sub>3</sub> + 5 wt% Te composition due to high carrier concentration (<i>n</i>) and good carrier mobility (<i>µ</i>). Microstructural analysis revealed the formation of densely interconnected polycrystalline grains featuring fine grain boundaries, planar/point defects, and strain field domains, contributing towards wide-length scale phonon scattering. The cumulative effect of drastically reduced thermal conductivity (κ ~ 0.8&#xa0;W/m-K at 300&#xa0;K), and enhanced power factor resulted in a record <i>zT</i> value ~ 2.2 at 300&#xa0;K in Bi<sub>0.5</sub>Sb<sub>1.5</sub>Te<sub>3</sub> + 5 wt% Te, with an average <i>zT</i> value up to 1.35 in temperatures ranging from 303 to 573&#xa0;K. The COMSOL simulations predict a maximum conversion efficiency (<i>η</i><sub><i>max</i></sub>) of ~ 15%, at a temperature gradient (<i>∆T</i>) of 270&#xa0;K, for a single-leg thermoelectric generator (TEG) developed using this material.</p>

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Strategic control of excess tellurium to achieve high figure-of-merit in Te-rich Bi0.5Sb1.5Te3

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  • 发表日期：

    2025年2月6日

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  • Ranu Bhatt,
  • Rishikesh Kumar,
  • Pramod Bhatt,
  • Pankaj Patro,
  • Shovit Bhattacharya,
  • Mani Navaneethan,
  • Soumen Samanta,
  • Ajay Singh

摘要

Increasing the Te content in stoichiometric Bi0.5Sb1.5Te3 facilitates effective control over the anti-site defects and nanostructure; however, arresting excess Te in the host matrix is challenging. Herein, we report the success of a saturation-annealing treatment in a vacuum, followed by air-quenching as a promising approach for synthesizing high figure-of-merit (zT) Bi0.5Sb1.5Te3+xTe (x = 0, 2, 5 and 10 wt%) materials. A remarkably high-power factor (α2σ ~ 6 mW at 300 K) is achieved in p-type Bi0.5Sb1.5Te3 + 5 wt% Te composition due to high carrier concentration (n) and good carrier mobility (µ). Microstructural analysis revealed the formation of densely interconnected polycrystalline grains featuring fine grain boundaries, planar/point defects, and strain field domains, contributing towards wide-length scale phonon scattering. The cumulative effect of drastically reduced thermal conductivity (κ ~ 0.8 W/m-K at 300 K), and enhanced power factor resulted in a record zT value ~ 2.2 at 300 K in Bi0.5Sb1.5Te3 + 5 wt% Te, with an average zT value up to 1.35 in temperatures ranging from 303 to 573 K. The COMSOL simulations predict a maximum conversion efficiency (ηmax) of ~ 15%, at a temperature gradient (∆T) of 270 K, for a single-leg thermoelectric generator (TEG) developed using this material.