Abstract
Rock-salt scandium nitride has gained interest due to its thermoelectric properties including a relatively high Seebeck coefficient. This motivates research for other semiconductor materials that exhibit similar electronic structure features as ScN. Using density functional theory calculations, we have studied disordered solid solutions of (Zr0.5, Mg0.5)N and (Hf0.5, Mg0.5)N using the special quasi-random structure model. The results show that within a mean-field approximation for the configurational entropy, the order–disorder phase transformation between the monoclinic LiUN2 prototype structure and the rock-salt cubic random alloy of these mentioned solid solutions occur at 740 K and 1005 K for (Zr0.5, Mg0.5)N and (Hf0.5, Mg0.5)N, respectively. The density-of-states for the two ternary compounds is also calculated and predicts semiconducting behavior with band gaps of 0.75 eV for (Zr0.5, Mg0.5)N and 0.92 eV for (Hf0.5, Mg0.5)N. The thermoelectric properties of both compounds are also predicted. We find that in the range of a moderate change in the Fermi level, a high Seebeck coefficient value at room temperature can be achieved.
Highlights
The aim to decrease reliance on fossil fuels has led to research on energy harvesting, for example of thermal and solar energy
In addition to a high Seebeck coefficient and electrical conductivity, features such as chemical stability, non-toxicity and ease of manufacturing are of importance when choosing an appropriate thermoelectric material
We investigate the configurationally disordered solid solutions (Zr0.5, Mg0.5)N and (Hf0.5, Mg0.5)N using the special quasi-random structure (SQS) method in conjunction with density functional theory (DFT) calculations
Summary
The aim to decrease reliance on fossil fuels has led to research on energy harvesting, for example of thermal and solar energy. Predicted thermoelectric properties of the semiconducting compounds showed that in the range of a moderate change in the Fermi level, high room temperature Seebeck coefficient values can be achieved. By comparing the formation energy of the disordered alloys of (Zr0.5, Mg0.5)N and (Hf0.5, Mg0.5)N in the rock-salt cubic structure with that of its LiUN2 ordered structure counterparts, the order/ disorder transition temperature can be calculated within a mean-field approximation.
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