Investigation of a ternary Zintl phase KBaBi: synthesis, crystal structure, and preliminary transport properties

The first experimental realization of KBaBi, a ternary Zintl compound theoretically predicted to exhibit promising thermoelectric properties, is reported. Single crystals were successfully synthesized from constituent elements, and structural analysis revealed that KBaBi crystallizes in a hexagonal ZrBeSi‐type structure (space group P63/mmc, Z = 2) with lattice parameters a = 6.0884(5) Å and c = 7.4868(6) Å at 300 K. In this structure, Ba and Bi atoms form planar honeycomb lattices stacked along the c‐axis with K‐atom layers sandwiched between them. Notably, K atoms exhibit remarkably large thermal vibrations, with the equivalent isotropic atomic displacement parameter approximately twice those of Ba and Bi atoms in the temperature range of 100–300 K, suggesting potential "rattling" behavior beneficial for thermoelectric performance. Transport measurements on a sintered polycrystalline sample (70% relative density) revealed electrical resistivity increasing from 3.89 to 8.56 mΩ cm and positive Seebeck coefficients ranging from 48.8 to 88.1 µV K−1between 296–486 K, indicating that KBaBi is a p‐type narrow‐gap semiconductor.