Effect of Zn substitution at a Cu site on the transport behavior and thermoelectric properties in Cu3SbSe4

Abstract

An attempt is made in this study to find the effect of substitution of Zn at a Cu site in copper antimony selenide (Cu_3−xZn_xSbSe₄; x = 0, 0.5, 1.0), prepared using a conventional melt growth followed by spark plasma sintering, with the aim of investigating the transport behavior and thermoelectric properties. A single parabolic band model with acoustic phonon scattering approximation was used to explain the transport phenomenon and density of states effective mass. The intrinsic samples (x = 0) show unipolar transport with holes as majority charge carriers. It was found that both the effective mass and carrier concentration decreased with increase in Zn concentration. From thermal conductivity measurements, evidence of bipolar carrier transport is found above 475 K in Zn containing samples and thus the possibility of involvement of other scattering mechanisms along with acoustic phonons is not ruled out. The Seebeck coefficient of the samples containing Zn show a negative value above 600 K whereby it is observed that substitution of Cu with Zn contributes electronic charge carriers in Cu_3−xZn_xSbSe₄. The value of the thermoelectric figure of merit (ZT) in Zn substituted samples first increases till 475 K and then starts to decrease sharply due to bipolar charge transport, however, Cu_2.5Zn_0.5SbSe₄ (x = 0.5) shows the highest ZT compared to other samples.