High thermoelectric performance of a defect in α-In₂Se₃-based solid solution upon substitution of Zn for In

Abstract

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 ).

Improvement of thermoelectric performance of α-In2Se3upon S incorporation

“…However, the S incorporation in In 2 Se 3 leads to the rearrangement of both the cationic and anionic disorders, such as those of nonstoichiometric V Se , V In , and/or interstitial In i , though we have difficulty in directly measuring the concentrations of such defects in the materials. The rearrangement of disorders facilitates the positional interchange between cations and vacancies, and avoids the annihilation of the defects, such as V In and interstitial In i acting as donors and thereby enhances the carrier concentration. To elucidate this phenomenon, we have specially measured the carrier concentrations ( n ) at RT, and the results are shown in Table .…”

“…The as‐solidified ingots were pulverized and then ball milled in stainless‐steel bowls containing benzinum at a rotation rate of 350 rpm for 5 h. The dried powders were sintered using a spark plasma sintering apparatus (SPS‐1030) under a pressure of 55 MPa and at the highest temperature of ∼923 K. The total sintering time is less than 2 min, which includes 20 s of holding time, 10 s each at ∼470 and 923 K, respectively. Such rapid cooling and sintering procedures could fix the impurity (S) in the Se L and V Se , and avoid the phase transition and annealing effect caused by the interdiffusion of elements . The densities ( d ) of the sintered samples (5.41–5.46 × 10 3 kg m −3 ), which are about 95% theoretical values , were measured using Archimedes' method.…”

“…The lattice contributions ( κ L ) were obtained by subtracting the electronic part ( κ e ) from the total κ , i.e., κ L = κ − κ e . Here, κ e is expressed by the Wiedemann–Franz law, κ e = L 0 σT , where L 0 is the Lorenz number, estimated at ∼1.5 × 10 −8 WΩK −2 , as the virgin α‐In 2 Se 3 with a simple parabolic band model are close to nondegenerate limit . The parameters were finalized after several repeated measurements using different samples.…”

Enhanced thermoelectric performance via the solid solution formation: The case of pseudobinary alloy (Cu2Te)(Ga2Te3)3 upon Sb substitution for Cu

“…), have been reported in earlier publications. 21,25 3. Results and discussion 3.1 X-ray diffraction patterns and chemical compositional analyses Fig.S1 shows the x-ray diffraction patterns of powders (Cu2(1-x)Sb2xTe)(Ga2Te3)3 with x=0~0.2, in which materials exhibit the pure phase of CTGT-based solid solution (PDF:058-0248) in the composition range x=0~0.1.…”

“…(Cu2Te)(Ga2Te3)3 (denominated as CTGT), one fifth of the cation sites are structural vacancies. The carrier concentration (nH) in CTGT at room temperature (RT) reaches 0.53～1.2×10 25 18 . While at y=0.5, none of the cation sites are structural vacancies, the nH value at RT is only 2.1×10 24 m -3 .In addition, the κ value of the former (κ≈1.1 Wm -1 K -1 ) is lower than that of the latter (κ≈2.2 Wm -1 K -1 ) at 750 K. 19 Hence, the former should have a more prospective to be a potential TE candidate than the latter.…”