Thermoelectric Properties of Polycrystalline SrZn2Sb2 Prepared by Spark Plasma Sintering

Abstract

Compact polycrystalline samples of SrZn 2 Sb 2 [space group P3m1, a = 4.503(1) Å , c = 7.721(1) Å ] were prepared by spark plasma sintering. Thermoelectric performance, Hall effect, and magnetic properties were investigated in the temperature range from 2 K to 650 K. The thermoelectric figure of merit ZT was found to increase with temperature up to ZT = 0.15 at 650 K. At this temperature the material showed a high Seebeck coefficient of +230 lV K À1 , low thermal conductivity of 1.3 W m À1 K À1 , but rather low electrical conductivity of 54 S cm À1 , together with a complex temperature behavior. SrZn 2 Sb 2 is a diamagnetic p-type conductor with a carrier concentration of 5 9 10 18 cm À3 at 300 K. The electronic structure was calculated within the density-functional theory (DFT), revealing a low density of states (DOS) of 0.43 states eV À1 cell À1 at the Fermi level.

Designing high-performance layered thermoelectric materials through orbital engineering

“…Combining the selection criterion −0.06≤ Δ ≤0.06 and band gap E g <1.5 eV, we start the search for promising TE candidates from Zintl compounds. Besides those that have been confirmed by previous references18192021222324252627282930313233, compounds such as SrMg 2 Sb 2 , BaMg 2 Sb 2 , SrMg 2 Bi 2 and BaMg 2 Bi 2 are expected to show good electronic transport properties as well as TE performance. It is worthwhile to note that among these compounds potential TE candidates SrMg 2 Sb 2 and BaMg 2 Sb 2 contain earth-abundant, nontoxic and inexpensive elements.…”

“…Using the single parabolic band model and the assumption of acoustic phonon scattering mechanism, the values of μ 0 ( m */ m e ) 3/2 and maximum zT at optimal carrier concentrations for many reported CaAl 2 Si 2 -type Zintl compounds18202122232526272831323337 are calculated from published Hall data (Supplementary Table 1). The correlation between μ 0 ( m */ m e ) 3/2 (optimum zT ) and Δ is demonstrated in Supplementary Fig.…”

“…τ is the constant carrier relaxation time. ( b ) Experimental power factors18192021222324252627282930313233 α 2 σ at 600 K as a function of the crystal field splitting energy Δ in CaAl 2 Si 2 -type Zintl compounds. Solid solutions YbCd 1.6 Zn 0.4 Sb 2 and EuZn 1.8 Cd 0.2 Sb 2 with zT values1819 above unity are marked in red.…”

“…Here, taking layered CaAl 2 Si 2 -type Zintl compounds as an example, we combine first principles calculations and reported experimental data18192021222324252627282930313233 to demonstrate how the TE properties can be rationalized in terms of a simple crystal field scheme of orbitals splitting. Thereby, a powerful selection rule only based on band structure parameters is established as a simplified descriptor of electrical transport performance.…”

Ternary CaCu4P2-type pnictides AAg4Pn2 (A=Sr, Eu; Pn=As, Sb)

“…However, CaAl 2 Si 2 -type compounds have the potential to exhibit physical properties that are just as interesting as the more heavily investigated ThCr 2 Si 2 -type compounds. Within the ternary pnictide systems A-Zn-Pn, the antimonides AZn 2 Sb 2 (A ¼alkaline-earth metals such as Sr or divalent rare-earth metals such as Eu) have been recently identified as promising thermoelectric materials [2][3][4][5][6][7][8][9]. Furthermore, CaAl 2 Si 2 -type phases serve as an attractive platform to design other structures.…”