Non-technical summary Innovations in materials are at the center of recent technological advances. The ability to modify and control material structures, and understand their structure-property relationships can lead to exciting scientific discoveries and new technologies. In addition to pushing the boundaries of science, such advances lead to the improved prosperity of society. An important family of oxide materials are perovskite oxides. The structure and functional properties of these materials can be modified by different synthesis methods. With support from the Solid State and Materials Chemistry program in NSF’s Division of Materials Research and the Office of Strategic Initiatives, Prof. Ramezanipour at the University of Louisville, investigates the incorporation of oxygen-vacancies into perovskite oxides, where some of the positions that would typically be occupied by oxygen atoms are vacant. The distribution of these vacant sites in the material structure can be either random or ordered. In this project, several hypotheses are evaluated in an effort to understand how the ordering of oxygen-vacancies can be induced and controlled. Several chemical principles are used, such as the effect of electronic properties and geometric stability. Based on these criteria, a wide range of oxygen-deficient perovskites with different vacancy-arrangements and ordering patterns are synthesized, helping to establish guidelines for rational design of vacancy-ordered materials. Broad