No abstract

Through coordination of the Seebeck coefficient and carrier concentration in Cu3SnS4, TE performance improves significantly with the ZT value of 0.75 at 790 K.

I-III-VI2 chalcopyrites have unique inherent crystal structure defects, and hence are potential candidates for thermoelectric materials. Here, we identified mixed polyanionic/polycationic site defects (ZnIn(-), VCu(-), InCu(2+) and/or ZnCu(+)) upon Zn substitution for either Cu or In or both in CuInTe2, with the ZnIn(-) species originating from the preference of Zn for the cation 4b site. Because of the mutual reactions among these charged defects, Zn substitution in CuInTe2 alters the basic conducting mechanism, and simultaneously changes the lattice structure. The alteration of the lattice structure can be embodied in an increased anion position displacement (u) or a reduced bond length difference (Δd) between d(Cu-Te)4a and d(In-Te)4b with increasing Zn content. Because of this, the lattice distortion is diminished and the lattice thermal conductivity (κL) is enhanced. The material with simultaneous Zn substitution for both Cu and In had a low κL, thereby we attained the highest ZT value of 0.69 at 737 K, which is 1.65 times that of Zn-free CuInTe2.

In this project, we have successfully manipulated the lattice defects in α-In 2 Se 3 -based solid solutions (In 2-x Zn x Se 3 ) upon proper substitutions of Zn for In, via a non-equilibrium fabrication technology of materials (NEFT). The manipulation of the defects centers on reducing the number of interstitial In atoms (In i ) and Se vacancies (V Se ), and creating a new antisite defect Zn In as a donor. By such means, the lattice structure tends to be ordering, and also more stabilized than that of pure α-In 2 Se 3 . At the meantime, the carrier concentration (n) and mobility (µ) have increased by 1~2 orders of magnitude. As a consequence, the solid solution at x=0.01 gives the 10 highest TE figure of merit (ZT) of 1.23(±0.22) in the pressing direction at 916K, which is about 4.7 times that of virgin α-In 2 Se 3 (ZT=0.26). This achieved TE performance is mainly due to the remarkable improvement of the electrical conductivity that increases from 0.53×10 3 (Ω -1 m -1 ) at x=0 to 4.88×10 3 (Ω -1 m -1 ) at x=0.01 at 916K, in spite of the enhancement of the lattice thermal conductivity (κ L ) from 0.26 (wm -1 k -1 ) to 0.32 (wm -1 k -1 ).

We synthesized the solid solutions CuGa1−xInxTe2 (x = 0–1.0) by isoelectronic substitution of element In (Ga) for Ga(In) in the CuMTe2 (M = Ga, In) lattices and examined their thermoelectric properties. The structure upon substitution provides much high Seebeck coefficient (α), relatively low thermal (κ), and electrical conductivity (σ). AT 701 K, the α, σ, and κ are 283.15 µV K−1, 1.15 × 104 Ω−1 m−1, and 0.71 W m−1 K−1, respectively, for CuGa0.36In0.64Te2, which give the figure of merit (ZT) of 0.91, about two times those of the mother compounds CuGaTe2 and CuInTe2. This material holds great application perspectives at intermediate temperatures.