Crystal growth, thermoelectric properties, and electronic structure of AgBi ₃S ₅ and AgSb _xBi _3-xS ₅ (x = 0.3)

The compound AgBi ₃S ₅ (I) (synthetic pavonite) and its solid solution AgSb _xBi _3-xS ₅ (x = 0.3) (II) were prepared by direct combination of elemental Ag, Bi, Sb, and S. They crystallize in the monoclinic space group C2/m with a = 13.345(3) Å,b = 4.0416(8) Å, c = 16.439(3) Å, and β= 94.158(3)° for I and a = 13.302(4) Å, b = 4.0381(11) Å, c = 16.388(5) Å, and β= 94.347(5)° for II. The Bridgman technique was used to grow bulk crystals of these materials. The crystal structure refinements, physicochemical properties, and thermoelectric properties of these materials are presented. The thermoelectric power for AgBi ₃S ₅ and AgSb _0.3Bi _2.7S ₅ showed -64 and -98 μV/K, respectively, with room-temperature electrical conductivity of 489 and 260 S/cm. The thermal conductivity for both compounds at room temperature was measured to be very low at ∼1 W/m·K, respectively. Electronic band structure calculations for AgBi ₃S ₅ suggest the importance of silver d-states to the charge transport and also indicate the presence of an indirect energy gap.