Improvement of thermoelectric performance in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Sb</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>Te</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:mtext>/</mml:mtext><mml:mi>Te</mml:mi></mml:mrow></mml:math> composites

Te-impurity-incorporated ${\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}$, i.e., ${\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}+x\phantom{\rule{0.16em}{0ex}}\mathrm{mol}\phantom{\rule{0.16em}{0ex}}%$ Te ($x=0$, 4, 6, and 9) composites were synthesized by solid-state reaction technique. Analysis of x-ray diffraction indicates not only impurity as a second phase but also doping via suppression inherent vacancies in the ${\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}$ matrix. As result this change formation energy different types native defects due to synthesis Te-rich condition, carrier concentration $({n}_{\mathrm{H}})$ lower than pristine sample was observed. Low ${n}_{\mathrm{H}}$ along with gradual convergence valence bands progressive increases Seebeck coefficient $(S)$ Te-incorporated samples. Even though impurities increase electrical resistivity (\ensuremath{\rho}), enhanced texturing lattice planes ensures that charge mobility does degrade addition. result, maximum power factor $=17\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{W}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}2}$ at $T=480$ K for $x=6$ has been achieved. In addition, addition strengthens phonon scattering an phonon-phonon Umklapp point-defect-induced phonons. Due such strong scattering, thermal conductivity $(\ensuremath{\kappa})$ decreases, reduced $({\ensuremath{\kappa}}_{\mathrm{L}})$, low $0.28\phantom{\rule{0.16em}{0ex}}\mathrm{W}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ 500 $x=6$, simultaneous $S$ decrease \ensuremath{\kappa}, high $ZT\ensuremath{\sim}0.87$ 480 K, almost 33% higher host material,