CaCoSO diluted magnetic antiferromagnet semiconductor as efficient thermoelectric materials

Highlights: • CaCoSO exhibit direct (Γ^v- Γ^c) gap of about 2.187 eV for spin-up (↑). • CaCoSO exhibit direct (K^v-K^c) gap of about 1.187 eV for spin-down(↓). • An indirect gap (Γ^v-K^c) of about 0.4 eV for the spin-polarized CaCoSO. • Small gap turn CaCoSO to be as promising candidate for thermoelectric materials. - Abstract: We have reported the thermoelectric properties of the recently synthesized CaCoSO single crystal by Salter et al. in 2016. It is quite interesting to mention that CaCoSO single crystals exhibit a direct energy gap (Γ^v- Γ^c) of about 2.187 eV for the spin-up (↑) channel, which turns out to be a (K^v-K^c) direct gap of about 1.187 eV for the spin-down (↓) channel, resulting in an indirect gap (Γ^v-K^c) of about 0.4 eV for the spin-polarized CaCoSO single crystal. Such a small gap makes CaCoSO a promising candidate for thermoelectric materials. Calculations reveal a remarkable finding that the CaCoSO single crystal exhibits high electrical conductivity, low thermal conductivity and a large Seebeck coefficient; therefore, based on these findings, the CaCoSO single crystal may be considered an efficient thermoelectric material. The electron clouds of CaO₃S₄ and CoS₃O exhibit a planar shape with conjugated electron orbitals and exhibit a strong covalent Ca−O, Co−O bonding. This is another factor which makes CaCoSO a promising candidate for thermoelectric materials, since covalent bonding is more favorable for the transport of the carriers than ionic bonding. CaO₃S₄ and CoS₃O are the main sources for the thermoelectric generator in CaCoSO. Therefore, based on the above findings, we can conclude that CaCoSO could be a promising thermoelectric material.