Abstract Scope |
In complex oxides such as spinels, there are extra degrees of freedom related to the chemical order, or arrangement, of cations in the structure. This complicates the structure of grain boundaries, where we have seen that grain boundaries exhibit a higher intrinsic degree of chemical disorder than the surrounding matrix. Using atomistic modeling, we find that cation “inversion” is higher at grain boundaries in spinels, but that this level of inversion, which is sensitive to temperature, is also sensitive to the chemistry, with Fe-Cr spinels exhibiting lower levels of disorder at grain boundaries than Ni-Cr spinels. This is contrast to the bulk behavior. Further, when considering mixed Fe-Ni-Cr spinels, we find that there is a competition between chemical segregation and disorder at the grain boundaries. This has ramifications for functional properties, such as atomic transport, and thus must be accounted for when considering the structure-property relationships of these materials. |