Thermoelectric properties of chalcogenide based Cu2+xZnSn1−xSe4

Abstract

Quaternary chalcogenide compounds Cu2+xZnSn1−xSe4 (0 ≤ x ≤ 0.15) were prepared by solid state synthesis. Rietveld powder X-ray diffraction (XRD) refinements combined with Electron Probe Micro Analyses (EPMA, WDS-Wavelength Dispersive Spectroscopy) and Raman spectra of all samples confirmed the stannite structure (Cu2FeSnS4-type) as the main phase. In addition to the main phase, small amounts of secondary phases like ZnSe, CuSe and SnSe were observed. Transport properties of all samples were measured as a function of temperature in the range from 300 K to 720 K. The electrical resistivity of all samples decreases with an increase in Cu content except for Cu2.1ZnSn0.9Se4, most likely due to a higher content of the ZnSe. All samples showed positive Seebeck coefficients indicating that holes are the majority charge carriers. The thermal conductivity of doped samples was high compared to Cu2ZnSnSe4 and this may be due to the larger electronic contribution and the presence of the ZnSe phase in the doped samples. The maximum zT = 0.3 at 720 K occurs for Cu2.05ZnSn0.95Se4 for which a high-pressure torsion treatment resulted in an enhancement of zT by 30% at 625 K.

The effect of Cu addition on the thermoelectric properties of Cu2CdGeSe4

“…Cu 2 Se 4 ) tetrahedral array acts as an electrical conducting unit and the other MTQ 4 (e.g. CdSnSe 4 ) tetrahedral array acts as an insulating unit [2]. This complexity in crystal structure leads to the suppression of thermal conductivity [1,2].…”

Heterovalent Substitution to Enrich Electrical Conductivity in Cu2CdSn1-xGaxSe4 Series for High Thermoelectric Performances

“…The reported ZT values for pure polycrystalline are 0.19 for Cu 2 CdSnSe 4 and 0.18 for Cu 2 ZnSnSe 4 4. Many efforts have been done to enhance the TE performance of these quaternary compounds by doping1467891011 and nanocrystalling3512131415161718. Nanocrystallization is an effective way to reduce the thermal conductivity, but the complex chemical procedure is not suitable for large scale production in commercial applications.…”

Enhanced Thermoelectric Performance of Cu2CdSnSe4 by Mn Doping: Experimental and First Principles Studies

“…Quaternary chalcogenides, especially, Cu 2 -II-IV-VI4 compounds have been investigated recently as promising lead free p -type thermoelectric materials for excellent thermoelectric power generation123456789. Cu 2 -II-IV-VI4 are also promising materials for the solar cell applications due to their suitable direct band gap E g ( E g = 1.44 eV for Cu 2 ZnSnSe 4 and E g = 0.96 eV for Cu 2 CdSnSe 4 ) and the high absorption coefficient for wave numbers around 105 cm −1 10.…”

“…These compounds are one of the members of the large chalcogen based zinc-blende derived structure compounds (such as Ga 2 Te 3 , AgGaTe 2 , AgInSnTe 4 , Cu 3 SbSe 4 , Cu 2 CdSnSe 4 , etc ) family, which are well known as the low thermal conductivity materials. What's more, the wide band gap property of such quaternary compounds also helps enhance their TE performances, because the conventional TE materials exhibit a narrow band gap in which a bipolar effect may reduce the thermoelectric efficiency8.…”

“…Those improvements include enhancing the electrical conductivity through doping/partial substitution and reducing the thermal conductivity by nanocrystalization5891112. Single crystal13, powder X-ray diffraction (XRD)14, and theoretical calculation15 reveal that Cu 2 CdSnSe 4 has a stannite type structure with the space group (S.G.) of I -42 m .…”