Experimental investigation of the predicted band structure modification of Mg2X (X: Si, Sn) thermoelectric materials due to scandium addition

Abstract

Experimental investigation of the predicted band structure modification of Mg 2 X (X: Si, Sn) thermoelectric materials due to scandium addition

Developing a two-parabolic band model for thermoelectric transport modelling using Mg2Sn as an example

“…Data for four Li-doped p-type [53] and four Sc-and/or Sb-doped n-type Mg 2 Sn [52] samples were taken from literature. Among the p-type samples, Li 0.03 Mg were identified as low doped.…”

“…n-type samples chosen for this work were nominally Sc-doped. However, Sc was found to be ineffective as a dopant and basically without effect on the electronic properties as it forms secondary phases (ScSn and ScSi) in the Mg 2 Sn matrix, presumably without dissolving into Mg 2 (Si,Sn) [52].…”

“…While the effect of ScSn or ScSi phases cannot be excluded, the effect is expected to be small as they form distinct islands and have a small volume percentage and therefore should not be of great consequence while attempting two-band modelling. Additionally, data for an undoped Mg 2 Sn sample [52] was available which showed p-type behavior in a large part of the temperature range and is displayed together with the Li-doped samples' data. were used to determine the DOS masses and deformation potential constants for the VB and CB respectively.…”

“…With respect to the second CB, the reported inter-band separation between the two CBs from ab-initio calculations for Mg 2 Sn ranges from 0.16 to 0.4 eV at 0 K [51], justifying neglecting the upper band at least as a starting point. Additionally, TE property data for Mg 2 Sn is available for both p-and n-type materials [52,53] in a wide range of carrier concentrations and temperatures. Finally, it should be pointed out that a 2PB modelling of Mg 2 Sn is not merely a theoretical exercise, because studying end members can lead to insights helpful for their more practically interesting solid solutions.…”

“…Finally, it should be pointed out that a 2PB modelling of Mg 2 Sn is not merely a theoretical exercise, because studying end members can lead to insights helpful for their more practically interesting solid solutions. Moreover, Mg 2 Sn has sparked some interest as a potential TE material in its own right due to its relatively high power factor for both n-and p-type material [40,[52][53][54].…”