Effect of alloying on thermal conductivity and thermoelectric properties of CoAsS and CoSbS

Abstract

The effect of alloying on the thermoelectric properties of cobaltite, CoAsS, and paracostibite, CoSbS, has been investigated in this study. Density functional theory and the Boltzmann transport equation have been applied to explore the role of phonon-phonon scattering and atomistic scattering due to alloying in phonon transport. An almost 44% reduction in thermal conductivity of CoAsSbS alloy compared to pure CoAsS and an ∼15% reduction in thermal conductivity of CoAsSbS compared to pure CoSbS were found. Simultaneously, the thermoelectric (TE) figure of merit (ZT) increased by ∼11% in p-type CoAsSbS alloy and ∼8% in n-type CoAsSbS alloy as compared to their base pure materials at 800 K. We found that by tuning the composition of CoAsSbS alloy, very similar ZT values for both p-type and n-type can be achieved in a large temperature range. We also calculated the TE properties of CoAsSeS and CoSbSSe alloys. This study will help in designing CoAsSbS based alloys for efficient thermoelectric devices.

Investigation of Some Physical Properties of CoAsS Crystal Under Pressure

“…The obtained result for the indirect band gap is 1.0583 eV for ground state, so cubic CoAsS has a semiconducting structure. The band gap values found in the literature are 0.75 eV (Kaura, 2017) and 0.849 eV (Jain, 2013). Figure 1 (a) shows that the main contribution for the density of states comes from the valence bands.…”

“…Fleet and Burns (Fleet, 1990) have studied twin boundaries that are incoherent and coherent toward X-ray diffraction in cobaltite. Kaur and Bera (Kaura, 2017) theoretically investigated the effect of alloying on the thermal conductivity and the thermoelectric properties of cobaltite, CoAsS. Here, we studied on cubic CoAsS in order to understand the effect of pressure on structural, electronic, optical, elastic and thermodynamic properties.…”

Copper Sulfides: Earth‐Abundant and Low‐Cost Thermoelectric Materials

“…Several approaches are introduced as modern concepts to improve the thermoelectric performance; these are design of alloys, [36][37][38][39][40][41][42][43][44] fabrication of heavy element compound, [12,[45][46][47] complex crystal structuring, [48,49] resonant level doping, [13,50] and so on, aiming to create PGEC. Despite all these classical approaches, there is one more important strategy called nanostructurization, which is proven to be very promising.…”

“…It has been proved on many compounds that, for illustration, alloying effects on thermoelectric properties of CoAsS have been studied recently where nearly 44% reduction in the thermal conductivity is observed in the CoAs 0.8 Sb 0.2 S alloy as compared to pure CoAsS, and as a result, the value of zT is increased almost by 11%. [36] Similarly, new kinds of materials such as high-entropy alloys are introduced to have reduced lattice thermal conductivity. Furthermore, the large crystals with a complex microstructure lower both total and the lattice thermal conductivities.…”

“…Alloying effect not only works for elemental mixtures but also for further alloying of the binary and ternary compounds. It has been proved on many compounds that, for illustration, alloying effects on thermoelectric properties of CoAsS have been studied recently where nearly 44% reduction in the thermal conductivity is observed in the CoAs 0.8 Sb 0.2 S alloy as compared to pure CoAsS, and as a result, the value of zT is increased almost by 11% . Similarly, new kinds of materials such as high‐entropy alloys are introduced to have reduced lattice thermal conductivity.…”