Elucidation of the Solution Synthesis and Growth of Non-Noble Metal TE3-Type Intermetallics (T = Fe, Co; E = Ga, In)

Abstract

Due to challenging synthetic routes, non-noble metal intermetallic nanomaterials are seldom studied despite having promising thermoelectric, magnetic, and catalytic properties. To initiate these materials’ further study, we present a facile, quick, and modifiable solution-based procedure for the synthesis of FeGa₃, CoGa₃, CoIn₃, and Fe_0.5Co_0.5Ga₃, which are characterized by pXRD, TEM, SEM, EDS, ICP-MS, and XPS. Reaction insights for these isostructural intermetallics demonstrate a reliance on long-chain secondary amines, fast injection rates, as well as select aluminum hydride reductants, such as diisobutylaluminum hydride (DIBAL-H), whereas other strong reductants like alkoxyaluminum hydrides and borohydrides inhibit the formation of Ga-containing intermetallics. Our results suggest that these reactions can be tailored to proceed through either a coreduction or rapid amalgamation (seeded growth) mechanism, in which liquid Ga nanoseeds are formed, followed by rapid diffusion of the first-row transition metals, leading to crystallization of a thermodynamically stable intermetallic. These results lay foundational groundwork for accessing and understanding other underexplored non-noble metal intermetallic nanomaterials, and we believe it may be succeeded by further developments to improve control over composition, morphology, and thus physical properties.