Mg₃(Bi,Sb)₂ single crystals towards high thermoelectric performance

Abstract

Ternary Mg3(Bi,Sb)2 single crystals showing high thermoelectric performance are for the first time grown by the Mg flux method.

High-Performance Mg 3 Sb 2- x Bi x Thermoelectrics: Progress and Perspective

“…Additionally, a direct revelation of the E g for a semiconductor is possible by carrying out the angle-resolved photoemission spectroscopy (ARPES) on its n -type single crystals [ 26 ]. Pan et al recently reported the ARPES study on n -type Mg 3 Sb 2 single crystal, from which a forbidden gap is clearly observed ( Figure 3(b) ) and an E g > 0.6eV is estimated for Mg 3 Sb 2 [ 48 ]. But since the conduction band was not observed, further study is necessary to accurately determine the real E g .…”

“…However, the relatively scarce element tellurium (see Table 1 ) is a potential impediment for the large-scale TE applications of V 2 VI 3 compounds. In recent years, Mg-based semiconductors, e.g., p -type α -MgAgSb [ 44 – 46 ] and n -type Mg 3 Sb 2- x Bi x [ 33 , 47 , 48 ], have been discovered with good TE performance near RT, comparable to V 2 VI 3 compounds. Magnesium is the 8th most abundant element in the earth's crust [ 49 ].…”

“…Fortunately, even near RT, n -type Mg 3 Sb 2- x Bi x also shows good zT of around 0.8 ( Figure 1(b) ), making it a promising alternative to the state-of-the-art n -type Bi 2 Te 3- x Se x for solid-state cooling application. Although only 4 years have passed since the discovery of n -type Mg 3 Sb 2- x Bi x , there are already many important advances achieved, including the improvement of TE performance [ 33 , 48 , 70 – 73 , 78 – 80 , 82 , 92 , 93 ], the understanding of the origin for good power factor [ 70 , 71 ] and intrinsically low κ [ 94 ], the revelation of the carrier scattering mechanism near RT [ 82 , 95 , 96 ], the increasing awareness of Mg defect chemistry [ 70 , 97 , 98 ], and even the successful attempt of TE module [ 33 ].…”

N-Type Mg 3 Sb 2- x Bi x Alloys as Promising Thermoelectric Materials

“…Therefore, the alloying concentration of Mg 3 Bi 2 is crucial for balancing the carrier mobility and the Seebeck coefficient, as well as the bipolar effect. Pan et al [ 33 ] showed the band evolution from Mg 3 Bi 2 to Mg 3 Sb 2 through angle-resolved photoemission spectroscopy (ARPES) combined with density functional theory (DFT) calculations, which also indicated the effectiveness of adjusting the Bi/Sb ratio in improving thermoelectric performance.…”

“…As discussed above, a Mg deficiency could easily induce a high Mg vacancy ( V Mg 2- ) concentration in the vicinity of the boundary and result in the depletion of free n-type carriers since V Mg 2- serves as an effective electron-killing defect ( Figure 3(d) ). Single-crystal n-type Mg 3 Sb 2 was thus grown and used to investigate the underlying charge-scattering mechanism [ 33 , 57 , 58 ]. As indicated in Figure 3(e) , acoustic phonon scattering dominates the charge transport in the single-crystal sample that lacks grain boundary electrical resistance, resulting in the sample's significantly increased weighted mobility near room temperature.…”