Electronic and transport properties of zintl phase AeMg2Pn2, Ae = Ca,Sr,Ba, Pn = As,Sb,Bi in relation to Mg3Sb2

Abstract

A combined high-pressure experimental and theoretical study of the electronic band-structure of scheelite-type AWO4 (A = Ca, Sr, Ba, Pb) compounds J. Appl. Phys. 110, 043703 (2011); 10.1063/1.3622322High-temperature electrical and thermal transport properties of fully filled skutterudites RFe4Sb12 (R = Ca, Sr, Ba, La, Ce, Pr, Nd, Eu, and Yb) J. Appl. Phys. 109, 063713 (2011); 10.1063/1.3553842 n -type electrical conduction in transparent thin films of delafossite-type AgInO 2First principles calculations of the electronic structure and transport properties of Zintl phase AeMg 2 Pn 2 , Ae ¼ Ca,Sr,Ba, Pn ¼ As,Sb,Bi compounds and Mg 3 Sb 2 are reported. These are discussed in relation to the thermoelectric performance of the compounds and specifically the optimization of carrier concentration. It is found that there are several promising compositions and that the materials that have been studied to date are not fully optimized in terms of carrier concentration and may not ultimately be the best thermoelectrics in this family. We additionally report optical properties and show that there are significant differences among the compounds arising from differences in electronic structure and that these differences should be accessible to experiment. This provides a way to test the trends observed here. V C 2013 AIP Publishing LLC.

Insights into the design of thermoelectric Mg3Sb2 and its analogs by combining theory and experiment

“…The electronic structure of Mg 3 Sb 2 has been studied using different theoretical methods in various reports. Traditional functionals such as GGA 108 or LDA 109 are known to underestimate band gaps while recent calculations 54,74 with the TB-mBJ potential 110 gives more accurate band gaps close to the experimental values. However, band structures in all earlier reports are typically calculated along the high-symmetry k paths, [74][75][76][77] which often overlook the actual CBM at the lowsymmetry k point.…”

“…Traditional functionals such as GGA 108 or LDA 109 are known to underestimate band gaps while recent calculations 54,74 with the TB-mBJ potential 110 gives more accurate band gaps close to the experimental values. However, band structures in all earlier reports are typically calculated along the high-symmetry k paths, [74][75][76][77] which often overlook the actual CBM at the lowsymmetry k point. As revealed in the recent calculations including SOC by Zhang et al, 57 the accurate CBM in Mg 3 Sb 2 is located at the CB 1 point (0, 0.417, 0.333), which is along the M * -L * line inside the first Brillouin zone (see Fig.…”

Advances in Thermoelectric Mg3Sb2 and Its Derivatives

“…For instance, native defects do not enable sufficiently high carrier concentration in both n‐ and p‐type binary Mg 3 Sb 2 , even with the highest possible defect concentration . Actually, ternary AB 2 C 2 Zintl compounds have so far not been reported to show a n‐type conduction and some of them show a hole concentration being higher than that required for optimal thermoelectric performance by an order of magnitude. This indicates the necessity of additional extrinsic defects in Mg 3 Sb 2 and its derivatives (AB 2 C 2 ), to locate the carrier concentration in the optimal range for both conduction types in order to maximize the thermoelectric performance.…”

“…The promising thermoelectric performance realized in these compounds is enabled by the richness in composition for further manipulation of both electronic and thermal properties as well as by the intrinsic low lattice thermal conductivity. The general formula for this class of Zintl compounds can be written as AB 2 C 2 , where A can be alkaline earth or rare‐earth elements (e.g., Mg, Ca, Sr, Ba, Eu, Yb), B can be transition metals or main‐group elements (e.g., Cd, Zn, Mg, Mn, Al), and C can be Group IV/V elements (e.g., Sb, Bi). Such a broad variety in composition enables either a very low lattice thermal conductivity or a very high band degeneracy, as well as great availabilities for further manipulating the phonon and charge transport properties through the formation of solid solution .…”

Enhancing thermoelectric properties of a p-type Mg3Sb2- based Zintl phase compound by Pb substitution in the anionic framework

“…ZT z 0.55 at 600 K by Kajikawa et al 55 and ZT z 0.21 at 875 K by Condron et al 56 ) no signicant progress has been made towards its viability for thermoelectric applications. However, recently, Singh et al 57 theoretically investigated the detailed electronic structure and transport properties of Zinlt phase Mg 3 Sb 2 and a series of alloys (AeMg 2 ) Pn 2 (Ae ¼ Ca, Sr, Ba; Pn ¼ As, Sb, Bi) compounds in relation to their thermoelectric performance. They claimed that the several promising compositions in this family are not fully optimized in terms of carrier concentration.…”