Synthesis and Characterization of Multinary Selenides A₄B₁₀Se₁₉ (A=Sn, Pb; B=Sb, Bi)

Multinary selenides A₄B₁₀Se₁₉ (A=Sn/Pb; B=Sb/Bi), including Sn₄Bi₁₀Se₁₉, Pb₄Sb_6.71Bi_3.29Se₁₉, and Pb₄Sb_3.43Bi_6.57Se₁₉, were prepared by solid-state reactions. These compounds adopt the Felbertalite structure type that crystallizes in the monoclinic space group C2/m (No. 12). Single-crystal and powder X-ray diffraction measurements studied the crystal structure and site preference of metal sites. They exhibit stacking of stepped layers (Formula presented.) (NaCl¹¹¹-type) and ribbon-shape (Formula presented.) (NaCl¹⁰⁰-type) units that are connected via shared Se²⁻ ions. Electronic structure calculations indicated semiconducting properties and were verified by temperature-dependent conductivity and Seebeck coefficient measurements. The thermoelectric properties show a maximum power factor of 1.06 μW ⋅ m⁻¹ ⋅ K⁻² at 550 K for Pb₄Sb₆Bi₄Se₁₉.