Realizing enhanced thermoelectric performance in an n-type Mg3(Bi,Sb)2-based film

Abstract

Zintl phase Mg₃(Bi,Sb)₂-based materials have garnered significant interest in recent times due to their potential in room-temperature thermoelectric applications. Recently, bulk n-type Mg₃(Bi,Sb)₂ alloy materials with high thermoelectric performance have been extensively studied. However, achieving reliable n-type conduction in thin films of these materials remains a challenge due to the formation of negatively charged Mg vacancies. Herein, we report the successful growth of n-type Mg₃Bi_2−xSb_x based composite films by incorporating additional Mg through co-sputtering. The impact of sputtered power and deposition temperature on the thermoelectric properties and conduction behavior of single-sputtered thin films was thoroughly investigated. Experimental results, including X-ray diffraction analysis and transport properties characterization, reveal that increasing sputtering power and deposition temperature yield p-type Bi-rich Mg₃(Bi,Sb)₂ thin films. Besides, n-type conduction is achieved by co-sputtering with Mg by forming a Mg-rich region within the Mg₃Bi_2−xSb_x thin film. The resulting Mg₃Bi_2−xSb_x composite film demonstrates a high Seebeck coefficient of −375 μV K⁻¹ at 373 K, leading to a maximum power factor of 132 μW m⁻¹ K⁻² at the same temperature. Our research examines the key role of Bi or Mg concentration in finely tuning the conduction properties of Mg₃Bi_2−xSb_x-based thin films. This progressive-edge investigation promises to unlock new avenues for the utilization of Mg₃(Bi,Sb)₂ thin films in developing low temperature thermoelectric applications.