Abstract
Owing to their unique crystal and band structures, in thermoelectrics increasing attention has recently been paid to compounds of the ternary I–III–VI chalcopyrite family. In this work, unequal bonding between cation and anion pairs in Cu1−yAgyIn3Se4.9Te0.1 solid solutions, which can be effectively used to disturb phonon transport, has been proposed. The unequal bonding, which is represented by the difference of bond lengths Δd, Δd = d(Cu–Se) − d(In–Se) and anion position displacement from its equilibrium position Δu = u − 0.25, is created by the isoelectronic substitution of Ag for Cu. At y = 0.2 both the Δd and Δu values reach their maxima, resulting in a remarkable reduction in lattice thermal conductivity (κL) and an improvement in TE performance. However, as the y value increase to 0.3 both Δd and Δu values decrease, causing the κL value to increase and the ZT value to decrease from 0.5 to 0.24 at 930 K. Accordingly, unequal bonding might be an alternative way to improve the TE performance of ternary chalcopyrites.
Highlights
Compounds of the ternary I–III–VI chalcopyrite family have been paid more and more attention in thermoelectrics (TE)[1,2,3] since they have two types of inherent feature structures, which are namely, crystal structure defects and band splitting
The unequal bonding, which is represented by the difference of bond lengths Dd, Dd 1⁄4 d(Cu–Se) À d(In–Se) and anion position displacement from its equilibrium position Du 1⁄4 u À 0.25, is created by the isoelectronic substitution of Ag for Cu
Based on the previous investigations,[16] in this work we have proposed an unequal bonding between Cu–Se and In–Se, which is inspired by the isoelectronic substitution Ag for Cu, in the Te– CuIn3Se5 system
Summary
Compounds of the ternary I–III–VI chalcopyrite family have been paid more and more attention in thermoelectrics (TE)[1,2,3] since they have two types of inherent feature structures, which are namely, crystal structure defects and band splitting. This alteration gives rise to a non-zero valence band split (DCF) along with the creation of the compression or tensile stress in the lattice. In this case, the anion position displacement u, u 1⁄4. In view of the above arguments, it is strongly necessary to clarify what role of the unequal bonding in ternary chalcopyrites plays in in uencing the carrier and phonon transport?. The existence of unequal bonding environment reduces the lattice thermal conductivity and improves the TE performance
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