Crystal Growth, Thermal Stability and Electrical Transport Property of Double‐Doping (SnCd) System in Single‐Crystal β‐Zn₄Sb₃

Abstract

In this work, the effect of Cd and Sn atoms partly substitution for Zn on among crystal growth, thermal stability, mechanical, and electrical transport property in β‐Zn4Sb3 is reported. In a series of samples prepared from the atomic ratios of Zn:Sb:Cd:Sn = 4.4:3:x:3 (x = 0.2, 0.4, 0.6, and 0.8). Carrier concentration of all samples varies from 4.52 × 1019 to 6.42 × 1019 cm−3 as carrier mobility changes from 58.27 to 67.93 cm2 V−1 s−1 at room temperature. As a result, electrical transport properties of the samples are optimized by CdSn co‐doped. The experimental density of all the samples varies from 6.26 × 103 to 6.34 × 103 kg m−3 consistent with the theoretical value. The weight loss and melting point of the sample are determined to discuss thermal stability in the heating process in air, indicating that the single crystals β‐Zn4Sb3 possess an excellent thermal stability and it is practical importance in the TE application at high temperature. Consequently, the maximal power factor of 1.70 × 10−3 W m−1 K−2 is achieved at 540 K for the sample with initial Cd content x = 0.2, which is enhanced by 40% compared with the single‐doping system in β‐Zn4Sb3.

High-Performance and Stable (Ag, Cd)-Containing ZnSb Thermoelectric Compounds

“…In the lattice, part of the Zn atoms is disorderly distributed among three crystallographically distinct interstitial sites ((0.0697, 0.2347, 0.1040), (0.2173, 0.0939, 0.0309), and (0.2310, 0.1170, 0.2320)) with low activation energies (11.07 kJ mol –1 ) that are comparable to that (9.16 kJ mol –1 ) of the diffusion of Ag in the fast ion conductor α-AgI. − Similar to Cu 2−δ X (X = S, Se, and Te), , Zn 4 Sb 3 satisfies the concept of “phonon-liquid electron-crystal”, displaying a very low lattice thermal conductivity (κ L ), e.g., 0.65 W K –1 m –1 , and decent electrical transport at room temperature . In the past decades, various dopants (e.g., Ag, Cu, Mg, Cd, Ga, In, Ge, and Pb) have been introduced into Zn 4 Sb 3 to optimize its TE performance. − High zT s above 1 were achieved at 550–700 K, making Zn 4 Sb 3 among the best intermediate temperature TE materials. However, Zn 4 Sb 3 is prone to decompose severely under an electric field and/or a temperature gradient, leading to the deposition of metallic Zn on the sample surface. ,, A similar phenomenon has also been observed in Cu 2−δ X-based compounds. , The poor stability under an electric field greatly limits the real applications of Zn 4 Sb 3 .…”