Role of annealing atmosphere on the crystal structure and composition of tetrahedrite–tennantite alloy nanoparticles†
Tetrahedrite–tennantite (TET–TEN, Cu12Sb4S13–Cu12As4S13) nanoparticle (NP) alloys spanning the entire Sb–As composition range were synthesized using a hot-injection method without any detectable impurities. Thin films of TET–TEN NPs were prepared from colloidal NP inks and heat treated in sulfur vapor, hydrogen sulfide, and nitrogen atmospheres. Under sulfur, the TET–TEN films were oxidized to tetragonal famatinite–luzonite (Cu3As1−xSbxS4). Heat treating under a reducing hydrogen sulfide atmosphere stabilized the mixed TET–TEN alloy compositions, though the endmember compositions partially decomposed via loss of volatile pnictogen sulfides. Losses of pnictogen and sulfur atoms were most significant when heat treating under an inert nitrogen atmosphere. Collectively, these results suggest that TET–TEN materials can be reversibly interconverted to famatinite–luzonite by selecting an appropriate annealing atmosphere. Our work serves as the foundation for both the synthesis and production of device-quality TET–TEN and related chalcogenide NP thin films.