Enhanced thermoelectric performance of n-type Mg3.2Sb1.5Bi0.5 by rare-earth elements (Er, Tb, Tm) doping into Mg site.

The n-type Mg 3.2 Sb 1.5 Bi 0.5 has emerged as a promising candidate for thermoelectric materials and has attracted significant research interest. However, effective n-type dopants have been predominantly limited to chalcogens. In our work, we found that rare-earth elements (Er, Tb, Tm) are highly effective dopants for n-type Mg 3.2 Sb 1.5 Bi 0.5. Through a combination of theoretical predictions and experimental validations, we demonstrate that these dopants significantly enhance the carrier concentration, leading to improved thermoelectric performance. Specifically, we employed direct ball milling and spark plasma sintering to introduce rare-earth elements at the Mg sites. Experimental results show that doping rare-earth elements in n-type Mg 3.2 Sb 1.5 Bi 0.5 has a higher carrier concentration (≈ 8.4 × 1019 cm−3), which is higher than that of chalcogen-doped samples (≈ 2 × 1019 cm−3). High power factor (S 2 σ) ≈ 16 μ W cm−1K−2 was obtained in rare-earth elements (Er, Tb, Tm) doped samples. Combined with the lowered lattice thermal conductivity due to the introduction of effective phonon scattering centers in Mg 3.2− x A x Sb 1.5 Bi 0.5 (A= Er, Tb, Tm) sample. Finally, the ZT values of all doped samples reached ≈ 1.44 at 750 K. The highest peak ZT is ≈ 1.65 at 750 K for Mg 3.195 Er 0.005 Sb 1.5 Bi 0.5. The rare-earth elements (Er, Tb, Tm) doped n-type Mg 3 Sb 1.5 Bi 0.5 has comparable thermoelectric performance with the chalcogen-doped n-type Mg 3 Sb 1.5 Bi 0.5 , exhibiting promising potential for practical applications. This present work offers a comprehensive understanding of the effect of cation site doping improves the thermoelectric properties of n-type Mg 3 Sb 2. [Display omitted] • Introducing Er, Tb, and Tm into Mg 3.2 Sb 1.5 Bi 0.5 shifts the Fermi level, enhancing electron provision. • Lanthanide doping at Mg sites is more effective than chalcogens at Sb sites for n-type doping. • Er doping creates point defects, scattering high-frequency phonons and reducing lattice conductivity. • The highest peak ZT is approx 1.65 at 750 K for Mg 3.195 Er 0.005 Sb 1.5 Bi 0.5. [ABSTRACT FROM AUTHOR]