Li₃Sb₇Se₁₂: A Pavonite Homologue with Ultralow Thermal Conductivity

Lithium-containing semiconductors have applications in solid-state batteries, thermoelectrics, and neutron detectors. Li₃Sb₇Se₁₂ is a new ternary semiconductor isostructural to the mineral benjaminite (Ag₃Sb₇S₁₂) crystallizing in monoclinic space group C2/m. Benjaminite belongs to the pavonite mineral family with the general formula M_n+1(Bi/Sb)₂Q_n+5 (n = 0-8), where n is the octahedral building block length consisting of face-sharing octahedra. Li₃Sb₇Se₁₂ belongs to n = 7, and it differs from benjaminite by exhibiting occupancy disorder between Li⁺ and Sb³⁺ atoms. It exhibits exceptionally low lattice thermal conductivities of 0.53-0.37 W m^-1 K^-1 in the temperature range 300-873 K and is a p-type semiconductor. Chemical bonding analysis using DFT calculations indicates that hierarchical bonding and the distorted coordination environment of antimony play a prominent role in its heat transport properties, leading to ultralow lattice thermal conductivity, while selenium dominates the electronic structure near the bandgap.