Enhanced Thermoelectric Efficiency in P-Type Mg3Sb2: Role of Monovalent Atoms Codoping at Mg sites

Minati Tiadi; Vikrant Trivedi; Santosh Kumar; P K Jain; Satyesh Kumar Yadav; R Gopalan; Dillip K Satapathy; Manjusha Battabyal

doi:10.1021/acsami.3c02151

Enhanced Thermoelectric Efficiency in P-Type Mg₃Sb₂: Role of Monovalent Atoms Codoping at Mg sites

ACS Appl Mater Interfaces. 2023 Apr 26;15(16):20175-20190. doi: 10.1021/acsami.3c02151. Epub 2023 Apr 17.

Authors

Minati Tiadi^{1

2}, Vikrant Trivedi^{1

3}, Santosh Kumar², P K Jain⁴, Satyesh Kumar Yadav⁵, R Gopalan^{1

3}, Dillip K Satapathy², Manjusha Battabyal¹

Affiliations

¹ International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), IIT M Research Park, Chennai 600113, India.
² Soft Materials Laboratory, Department of Physics, Indian Institute of Technology Madras, Chennai 600036, India.
³ Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600036, India.
⁴ International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005, Telangana, India.
⁵ Center for Atomistic Modeling and Materials Design, Indian Institute of Technology Madras, Chennai 600036, India.

PMID: 37067866
DOI: 10.1021/acsami.3c02151

Abstract

Due to natural abundance, low cost, and compatibility with sustainable green technology, Mg₃Sb₂-based Zintl compounds are comprehensively explored as potential thermoelectric materials for near-room temperature applications. The effective use of these materials in thermoelectric devices requires both p and n-type Mg₃Sb₂ having comparable thermoelectric efficiency. However, p-type Mg₃Sb₂ has inferior thermoelectric efficiency efficiency compared to its n-type counterpart due to low electrical conductivity $(\sim 10^{3} S m^{- 1})$ . Here, we show that codoping of monovalent atoms (Li-Ag, and Na-Ag) at the Mg site of Mg₃Sb₂ produces a synergistic effect and boosts the electrical conductivity, which enhances the thermoelectric properties of p-type Mg₃Sb₂. While, Ag prefers to occupy the Mg2 site, Li and Na are favorable at the Mg1 site of Mg₃Sb₂ lattice. Compared to Li-Ag codoping, Na-Ag codoping in Mg₃Sb₂ is found to be more effective for increasing the charge carrier concentration and significantly augmenting the electrical conductivity. The dominance of the three-phonon scattering mechanism in Li and Li-Ag doped Mg₃Sb₂ and the four-phonon scattering process for the Na and Na-Ag doped Mg₃Sb₂ are confirmed. Due to the simultaneous increase in electrical conductivity and decrease in thermal conductivity, the zT value ∼0.8 at 675 K achieved for Mg_2.975Na_0.02Ag_0.005Sb₂ is the highest value among p-type Mg₃Sb₂. Our work shows a constructive approach to enhance the zT of p-type Mg₃Sb₂ via monovalent atoms codoping at the Mg sites.

Keywords: Seebeck coefficient; formation energy; monovalent atoms codoping; p-type Mg3Sb2; phonon scattering mechanism; power factor; thermoelectric figure of merit.