Magnetism and Thermoelectric Properties of the Zintl Semiconductor: Eu₂₁Zn₄As₁₈

High Resolution Image Download MS PowerPoint Slide Compositional diversity and intriguing structural features have made Zintl phases excellent candidates as thermoelectric materials. Zintl phase with 21-4-18 composition has shown high thermoelectric performance in the mid- to high-temperature ranges. The complex crystal structure and favorable transport properties of these compounds indicate the potential for high thermoelectric efficiency. Arsenic-based Eu 21 Zn 4 As 18, belonging to the Ca 21 Mn 4 Sb 18 structure type, exhibits a semiconductor-like p-type transport behavior and has a calculated band gap of 0.49 eV. The compound is paramagnetic at high temperatures, with an antiferromagnetic transition occurring at T N = ∼10 K. The moment obtained from the Curie–Weiss data fit aligns with Eu 2+ ions. At the same time, the field-dependent measurement at 2 K indicates complex magnetic ordering with a saturation moment consistent with Eu 2+ ions. Pristine Eu 21 Zn 4 As 18 exhibits an ultralow lattice thermal conductivity of 0.40 W m –1 K –1 at 873 K. Electronic transport properties measurement shows evidence of bipolar conduction across much of the measured temperature range (450–780 K). However, the Seebeck coefficient remains extremely high (>440 μV K –1 ) across this range, indicating the potential for high zT if an appropriate dopant is found. This work represents the first report on the temperature-dependent thermal conductivity, Seebeck coefficient, and thermoelectric efficiency of the arsenic-containing Zintl phase with 21-4-18 composition, showcasing its promise for further optimization of the thermoelectric performance.