Eutectic Microstructure and Thermoelectric Properties of Mg2Sn

Abstract

Ingots of undoped and Ag-doped Mg 2 Sn were prepared from the melt using a rocking Bridgman furnace at different cooling rates: slow cooling (0.1 K/min), moderate cooling (1 K/min), and rapid quenching. The ingots show very different microstructure and thermoelectric properties. Slow-cooled ingots consist of large Mg 2 Sn crystals with minor inclusions. Moderate-cooled ingots show significant variation in composition and microstructure, with Mg-rich material at the topmost section of the ingot and Sn-rich material at the bottom surface of the ingot. Rapid quenching results in ingots with finely dispersed Mg + Mg 2 Sn eutectic microstructure in the form of lamellae 200 nm to 500 nm in thickness. Measurements of the Seebeck coefficient and electrical conductivity in the temperature range of T = 80 K to 700 K were carried out to establish correlations between the microstructure and the thermoelectric properties.

High power factor in epitaxial Mg2Sn thin films via Ga doping

“…4(a). These values are comparable with those reported for the bulk single crystal, 11,16,31 suggesting high quality of our thin films. In the literature, Mg-based II-IV semiconductor thin films have been reported to have lower values than the bulk material.…”

High quality Mg2Sn crystals prepared by RF induction melting

“…Although to achieve p-type doping the silver atom must be incorporated at substitution sites, it appears some silver reacts with Mg to form finely dispersed MgAg eutectic clusters and/or MgAg precipitates at lower Ag-content (images c, d) or fine interconnected MgAg threads at the highest silver content (image e). By contrast the ingots grown by the Bridgman method at different cooling rates showed significant variation in composition and microstructure [16]. The Bridgman samples BR1-BR5, which were prepared at a very slow growth rate (0.1 mm/min), are less uniform in microstructure as compared with the RF samples.…”

“…Recently we reported on the preparation and properties of single and large-grain polycrystalline Mg 2 Sn thermoelectric materials prepared by the Bridgman method [8,9,16,17]. Here, we report on the preparation of Mg 2 Sn ingots doped with Ag (0-1 at%) prepared by the RF induction melting.…”

Control of the Thermoelectric Properties of Mg2Sn Single Crystals via Point-Defect Engineering

“…In the present study, we focus on Mg 2 Sn with the same crystal structure as Mg 2 Si. Mg 2 Sn has been studied extensively as a potential TE material [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] . Xin et al 31 reported that an Sb-doped n-type polycrystalline Mg 2 Sn, Mg 2.15 Sn 0.98 Sb 0.02 exhibited a zT value of 0.53 at 650 K (κ and PF are 4.7 W/mK and 3.9 W/mK 2 , respectively).…”

“…Regarding the TE properties of pristine Mg 2 Sn, single crystals exhibited different S values depending on the preparation method, as shown in Table 1 [18][19][20][21][22][23] . Generally, different S values reflect differences in carrier concentration.…”