Strcture And Thermoelectric Properties Of Ternary Cu-In-Te-based Chaocogenides

In this paper,three derivatives of Cu-In-Te,Cu_2.5In_4.5Te₈,Cu_3.52In_4.16Te₈ and CuIn₅Te₈,have been successfully prepared by powder metallurgy,along with spark plasma sintering?SPS?technique.Besides,the structures and thermoelectric properties of Cu_2.5+xIn_4.5Te₈?x=0,0.05,0.1,0.15?,?Cu₂Te?_x(Cu_3.52In_4.16Te₈)?x=0,0.03,0.05,0.08,0.11?and?Cu₂Te?_x?CuIn₅Te₈??x=0,0.05,0.1,0.2,0.3,0.4,0.5?were extensively studied upon different dopings.The findings are summarized below:When Cu is doped into Cu_2.5In_4.5Te₈,that is,Cu_2.5+xIn_4.5Te₈?x=0,0.05,0.1,0.15?,the Hall carrier concentration?n_H?effectively increases,and the lattice thermal conductivity??_L?reduces.The enhancement of carrier concentration?n_H?is attributed to degenerate impurity band at G point in the valence band maximum?VBM?,while the extremely low?_L results from the increased lattice disorder.We thus obtained the minimum?_L value of only 0.23 WK^-1m^-11 in the sample at x=0.1 and 820 K,which is in good agreement with the calculation using the Callaway model.The highest thermoelectric figure of merit ZT is 0.84 for the material at x=0.1,which is about 0.38higher than that of the pristine Cu_2.5In_4.5Te₈;In?Cu₂Te?_x(Cu_3.52In_4.16Te₈)?x=0,0.03,0.05,0.08,0.11?material system,the extra Te atom exists in the lattice as interstitial Te,which results in the change of local symmetry around it,thus optimizes the phonon transport through localized"rattling"and effectively reduces the lattice thermal conductivity,which is as low as only 0.3WK^-1m^-1.Although the Hall carrier concentration reduces upon Cu₂Te addition due to the unpinning of the Fermi level?E_f?towards the conduction band minimum?CBM?,the power factor remains stable.Therefore,this material shows a figure of merit?ZT?as high as 1.65?±0.15?at 815 K,which is a 1.5 fold enhancement as compared with x=0 compound.This indicates that the material in study has a great prospective to be applied in industry;Upon addition of Cu₂Te in CuIn₅Te₈,the thermoelectric performance of the materials?Cu₂Te?_x?CuIn₅Te₈??x=0,0.05,0.1,0.2,0.3,0.4,0.5?is effectively improved.At 814K,the value of?increases from 0.34?10³?^-1m^-11 for x=0 to 2.02?10³?^-1m^-11 at x=0.4.The maximum ZT value is about 0.3?x=0.4,814K?,which is 3 fold enhancement as compared with x=0 compound at the corresponding temperature.