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<p>In this research work, Ge- and Te-doped Bi<sub>2.5</sub>Se<sub>2.5</sub> thermoelectric materials were successfully synthesized using a solid-state reaction route, and their structural, microstructural, thermal, and electrical transport properties were systematically investigated. Powder X-ray diffraction confirmed the formation of a single-phase rhombohedral structure (space group R-3̅m) for all compositions, indicating successful incorporation of Ge and Te dopants without altering the host crystal symmetry, while EDS analysis verified the intended elemental composition and absence of secondary phases. FESEM studies revealed grain refinement and increased defect density in the doped samples, particularly in the Ge–Te co-doped BGST system, suggesting enhanced carrier and phonon scattering. Temperature-dependent electrical resistivity and Seebeck coefficient measurements in the 30–400&#xa0;°C range demonstrated <i>n</i>-type semiconducting behavior for all samples. Te-doped Bi<sub>2.5</sub>Se<sub>2.5</sub> exhibited the lowest electrical resistivity due to enhanced carrier mobility, whereas Ge doping increased thermopower through carrier filtering effects. Notably, the BGST co-doped sample showed the highest Seebeck coefficient (~ − 112&#xa0;µV&#xa0;K<sup>−1</sup> at 300&#xa0;°C), representing an enhancement of ~ 22% over pristine Bi<sub>2.5</sub>Se<sub>2.5</sub>, while BST achieved the highest power factor (~ 800&#xa0;µW&#xa0;m⁻<sup>1</sup>&#xa0;K<sup>−2</sup>) at elevated temperatures. Charge transport analysis based on the small polaron hopping model revealed thermally activated defect-mediated conduction with low activation energies. Theoretical thermal conductivity analysis further demonstrated significant suppression of phonon transport in the BGST sample (~ 1.0 W m⁻<sup>1</sup>&#xa0;K<sup>−1</sup>) due to enhanced lattice distortion, alloy disorder, and defect scattering. Hall transport analysis indicated optimized carrier concentration and moderate Hall mobility in the co-doped system, confirming that dual-site defect engineering effectively tailors charge and thermal transport behavior in Bi<sub>2.5</sub>Se<sub>2.5</sub>-based thermoelectric materials.</p>

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Synergistic effects of Ge and Te doping on structural, electrical, and thermoelectric properties of Bi2.5Se2.5

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年6月3日

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  • Suchitra Puthran,
  • A. N. Prabhu,
  • Ashok Rao,
  • G. Poojitha,
  • Ganesh Shridhar Hegde

摘要

In this research work, Ge- and Te-doped Bi2.5Se2.5 thermoelectric materials were successfully synthesized using a solid-state reaction route, and their structural, microstructural, thermal, and electrical transport properties were systematically investigated. Powder X-ray diffraction confirmed the formation of a single-phase rhombohedral structure (space group R-3̅m) for all compositions, indicating successful incorporation of Ge and Te dopants without altering the host crystal symmetry, while EDS analysis verified the intended elemental composition and absence of secondary phases. FESEM studies revealed grain refinement and increased defect density in the doped samples, particularly in the Ge–Te co-doped BGST system, suggesting enhanced carrier and phonon scattering. Temperature-dependent electrical resistivity and Seebeck coefficient measurements in the 30–400 °C range demonstrated n-type semiconducting behavior for all samples. Te-doped Bi2.5Se2.5 exhibited the lowest electrical resistivity due to enhanced carrier mobility, whereas Ge doping increased thermopower through carrier filtering effects. Notably, the BGST co-doped sample showed the highest Seebeck coefficient (~ − 112 µV K−1 at 300 °C), representing an enhancement of ~ 22% over pristine Bi2.5Se2.5, while BST achieved the highest power factor (~ 800 µW m⁻1 K−2) at elevated temperatures. Charge transport analysis based on the small polaron hopping model revealed thermally activated defect-mediated conduction with low activation energies. Theoretical thermal conductivity analysis further demonstrated significant suppression of phonon transport in the BGST sample (~ 1.0 W m⁻1 K−1) due to enhanced lattice distortion, alloy disorder, and defect scattering. Hall transport analysis indicated optimized carrier concentration and moderate Hall mobility in the co-doped system, confirming that dual-site defect engineering effectively tailors charge and thermal transport behavior in Bi2.5Se2.5-based thermoelectric materials.