| Abstract Scope |
Entropy-stabilized oxides (ESOs) provide a model system for studying how minor compositional heterogeneities influence phase transformations. In the (Co,Cu,Mg,Ni,Zn)O ESO, decomposition from a metastable single-phase rocksalt structure occurs through precipitation of a Cu-rich tenorite phase. Here, we report the effects of impurities during continuous cooling of (Co,Cu,Mg,Ni,Zn)O ESO through the transformation regime using electron microscopy. Precipitation occurs preferentially by heterogeneous nucleation in regions adjacent to impurities, pores and grain boundaries, demonstrating that minor chemical heterogeneities strongly influence nucleation behavior and transformation pathways. The resulting tenorite precipitates exhibit paired high-aspect-ratio laths emanating from a central spheroidal nucleus. Our observations indicate that impurities promote heterogeneous nucleation of a Cu-rich precursor phase at local Cu-rich regions, followed by transformation to spheroidal tenorite with a multi-domain structure that partially accommodates the transformation strains, and then branched growth of the domains to form laths in response to the differences in elastic moduli of the phases. |