High thermoelectric performance of n-type Mg3Bi2 films deposited by magnetron sputtering

Abstract

Mg3Bi2 are of great interest for thermoelectric applications near room temperature. In this paper, A metastable cubic phase(c-Mg3Bi2) films were prepared on glass substrate using Mg and Bi elemental targets by magnetron sputtering. Investigations were done on the phase composition, microstructure and thermoelectric properties of films that were deposited with various atomic ratios of Bi to Mg. When the atomic ratio of Mg/Bi exceeded the stoichiometry of 3:2, the films displayed a metastable cubic phase (c-Mg3Bi2) with a highly (111) preferred orientation. The deposited (c-Mg3Bi2) films possess n-type conductivity characteristics with high carrier mobility. In the temperature range of 300–490 K, a state-of-the-art average PF of 3.11 μW cm−1K−2 is attained in a 23 at.% Bi film. A fully Mg3Bi2 thermoelectric device consisting of both n-type and p-type Mg3Bi2 thin films is fabricated. It demonstrates a maximum output power density of 239 μW cm−2 at a temperature difference of 20 K. This work offers an effective approach to development of thermoelectric devices based on Mg3Bi2 materials.