Structures And Thermoelectric Performance Of Ternary Cu-In-Te Based Semiconductors

In this work,Cu_1.15In_2.29Te₄ and Cu₃In₅Te₉ based compounds are successfully synthesized by powder metallurgy method,and their thermoelectric performance are markedly enhanced by alloying Cu₂Te and substitution of Ga for In.Specifically,in Cu₂Te alloyed Cu_1.15In_2.29Te₄,we have observed the unpinning of Fermi level?E_f?and an impurity level created near the valence band,which enhance the carrier concentration and electric conductivity.Besides,the localized modes of Te interstitial defects hybridize with the acoustic modes of host In and Te,which leads to the enhanced scattering of thermal phonons,and results in the significantly low lattice conductivity??_L?.Eventually,a high thermoelectric performance with the highest ZT value around¹.0 at 855 K was obtained.Besides,in Cu₃In₅Te₉ based solid solutions with excess Cu,we observed a significant improvement in electrical conductivity but with limited decreasing of Seebeck coefficient upon Ga substitution for In.Meanwhile,lattice anharmonicity enhances and the lattice thermal conductivity??_L?reduces,due to the lattice distortion through the formation of solid solution.As a consequence,the highest ZT value of 0.77 at 825K is obtained.Finally,in Cu alloyed Cu₃In₅Te₉,we observed the improvement in the carrier concentration and electric conductivity,but a limited decrease in Seebeck coefficient.Simultaneously,the reduction of V_Cuu concentration alters the phonon scattering,leading to a lower lattice thermal conductivity??_L?and a high ZT value?¹.0?at 825 K.