Experimental and theoretical investigation of Cr1-xScxN solid solutions for thermoelectrics

The ScN- and CrN-based transition-metal nitrides have recently emerged as a novel and unexpected class of materials forthermoelectrics. These materials constitute well-defined model systems for investigating mixing thermodynamics, phase stability, and band structure aiming for property tailoring. Here, we demonstrate an approach to tailor theirthermoelectric properties bysolid solutions. The trends in mixing thermodynamics and densities-of-states (DOS) of rocksalt-Cr1-xScxNsolid solutions (0  ≤ x ≤ 1) are investigated by first-principles calculations, and Cr1-xScxNthin films are synthesized by magnetron sputtering. Pure CrN exhibits a high power factor, 1.7  × 10−3 W m−1 K−2 at 720  K, enabled by a high electron concentration thermally activated from N vacancies. Disordered rocksalt-Cr1-xScxNsolid solutions are thermodynamically stable, and calculated DOS suggest the possibility for power-factor improvement by Sc3d orbital delocalization on Cr3d electrons giving decreasingelectrical resistivity, while localized Cr3d orbitals with a large DOS slope may yield an improved Seebeck coefficient. Sc-richsolid solutions show a large improvement in power factor compared to pure ScN, and allfilms have power factors above that expected from the rule-of-mixture. These results corroborate the theoretical predictions and enable tailoring and understanding ofstructure-transport-property correlations of Cr1-xScxN.

Source: Journal of Applied Physics - December 1, 2016 Category: Physics Authors: Sit Kerdsongpanya, Bo Sun, Fredrik Eriksson, Jens Jensen, Jun Lu, Yee Kan Koh, Ngo Van Nong, Benjamin Balke, Bj örn Alling and Per Eklund Source Type: research