Vacancy filling effect in thermoelectric NbO

Area of Science:

• Materials Science
• Solid State Physics
• Computational Materials Science

Background:

• Niobium oxide (NbO) is a promising material for thermoelectric applications.
• Optimizing the Seebeck coefficient is crucial for improving thermoelectric performance.

Purpose of the Study:

• To investigate the effect of vacancy filling in NbO with Niobium (Nb) and Nitrogen (N) on the Seebeck coefficient.
• To design novel NbO-based compounds with enhanced thermoelectric properties.

Main Methods:

• Systematic exploration using density functional theory (DFT) calculations.
• Investigating vacancy filling at 1a and 1b Wyckoff sites in NbO.
• Experimental validation using reactively sputtered thin films.

Main Results:

• Filling the 1b Wyckoff sites with Nitrogen (N) resulted in a fivefold increase in the Seebeck coefficient.
• Nb d-nonmetal p hybridization was identified as the mechanism, inducing quantum confinement.
• Electrically conductive oxynitrides showed a Seebeck coefficient of -70 µV K⁻¹ at 800 °C.

Conclusions:

• Nitrogen incorporation into NbO's 1b Wyckoff sites is a highly effective strategy for enhancing the Seebeck coefficient.
• The observed enhancement is attributed to quantum confinement effects arising from Nb d-nonmetal p hybridization.
• These findings establish a new record for the Seebeck coefficient in NbO-based compounds, paving the way for advanced thermoelectric materials.