A simple chemical guide for finding novel n-type dopable Zintl pnictide thermoelectric materials

Abstract

Computations have predicted good thermoelectric performance of n-type doped Zintl phases. We present a simple, yet effective, chemical guide for finding n-type dopable Zintl pnictides and perform a large-scale search to identify candidate materials.

Doping by design: finding new n-type dopable ABX4 Zintl phases for thermoelectrics

“…The existence of cation vacancies with low formation energy is the primary cause of self p-type doping or difficulty in n-type doping in Zintl phases. 18 As such, Zintl phases where cation vacancies have high formation energies are considered n-type dopable. While n-type dopable Zintl phases are rare, we show here that our targeted search has enabled us to "design" as-yet-unknown Zintl phases with the desired doping characteristics as well as thermoelectric performance.…”

“…For example, DE don for Ca 5 Al 2 Sb 6 is -0.1 eV. 18 NaAlSb 4 : The formation energies (DH D,q ) of native point defects under Na-rich growth condition are shown in Figure 8(a). The lowest-energy acceptor defects are sodium vacancies V Na and donors are anti-site defects Sb Al and Na interstitials Na i .…”

High‐Density Frenkel Defects as Origin of N‐Type Thermoelectric Performance and Low Thermal Conductivity in Mg3Sb2‐Based Materials

“…[ 11 ] The discovery of n‐type Mg 3 Sb 2 was surprising because other numerous Zintl compounds are persistently p‐type due to charged cation vacancies that pin the Fermi level near valence bands. [ 12,13 ] The finding provided a striking example that, in intermetallic compounds, a slight deviation of nominal composition from stoichiometry notably changes a thermodynamic state and dopant stability. [ 4,14 ] To clarify how the off‐stoichiometry in composition influences defect formation and electronic structures of Mg 3 Sb 2 , a variety of mechanisms were proposed using defect calculations, [ 11,14–16 ] but these hypotheses lack experimental validation.…”

Computational discovery of promising new n-type dopable ABX Zintl thermoelectric materials

“…Within Zintl pnictides, it is not uncommon for both antimonide and bismuthide phases to exist. Examples include Mg 3 (Sb,Bi) 2 , 46 Yb 14 Mn(Sb,Bi) 11 , 9 K(Sb,Bi), 30 and Cs(Sb,Bi). 30 With underexploration comes opportunities.…”

“…Examples include Mg 3 (Sb,Bi) 2 , 46 Yb 14 Mn(Sb,Bi) 11 , 9 K(Sb,Bi), 30 and Cs(Sb,Bi). 30 With underexploration comes opportunities. Therefore, the chemical space considered in this study presents a fertile search landscape to discover new ABX Zintl phases.…”