High entropy oxide (Co,Cu,Mg,Ni,Zn)O exhibits grain size dependent room temperature deformation

Despite their vast composition space and promising properties, little is known about the fundamental mechanical behavior of high entropy oxides (HEOs). Here we provide experimental evidence of the nanoscale origin of room temperature deformation in (Co,Cu,Mg,Ni,Zn)O HEOs with different grain sizes. We find that micron-grain (Co,Cu,Mg,Ni,Zn)O deforms predominately through extensive <110>{1–10} dislocation slip manifesting as discrete slip bands. Nano-grain (Co,Cu,Mg,Ni,Zn)O, in addition to moderate dislocation slip activity, deforms through grain boundary sliding and intergranular cracking. The significant dislocation-mediated deformation and grain size dependent behavior demonstrates that HEOs have the potential for diverse and highly tailorable mechanical behavior. GRAPHICAL ABSTRACT IMPACT STATEMENT High entropy oxides (Co,Cu,Mg,Ni,Zn)O exhibit grain size dependent room temperature deformation, with micron-grain samples displaying significant potential for dislocation-mediated deformation and nanocrystalline samples exhibiting grain boundary sliding and micro-cracking.