Layered Hybrid Selenoantimonates with Reduced Thermal Conductivity

Four ternary selenoantimonates, Ag2SbSe3(enH) (I), KCu2SbSe3 (II), Cu2SbSe3(pdaH2)0.5 (III), and Cu2SbSe3(bdaH2)0.5 (IV) (en = ethylenediamine, pda = propanediamine, bda = butanediamine) were synthesized by solvothermal reactions using amines as solvents. The structures consist of M/Sb (M = Cu, Ag) intermetallic layers connected by either protonated amines or potassium ions. The optical bandgaps of these compounds were estimated from their optical absorption spectra (Kubelka-Munk function) with the values ranging from 0.9 to 1.8 eV. Thermal conductivity measurements were carried out on I, III, and IV, as well as on related compounds Cu2SbSe3(en)0.5 and Cu2SbSe3(en). In comparison with the inorganic counterpart compound CuSbSe2, the hybrid structures clearly show significantly reduced thermal conductivity, as a result of incorporation of inorganic-organic interface. The study demonstrates an effective approach to enhance the thermoelectric efficiency of such material systems.