(134d) Effects of Crystal Structure, Oxidation State, Vacancy Concentration and Composition On Perovskite Reactivity

Perovskites (ABO3) are oxides with highly tunable reactivity through the composition (A and B). We have systematically investigated how the A (K, Sr, La)and B (Ti, V, Cr, Mn, Fe, Co, Ni, Cu) sites modify the reducibility of perovskites in different crystal structures for applications as chemical looping oxygen carriers.  We will show how to systematically modify the reducibility by changing the d-band filling of the B-atom, by changing the oxidation state of the B-atom through choice of the A-atom, and the effects of changing crystal structure. We found a strong oxygen vacancy concentration dependence of the reducibility; the oxides get more difficult to reduce with increasing vacancy concentration. Finally, there was a moderate dependence of the reducibility on the crystal structure (cubic, rhombohedral and orthorhombic). We will also show how the surface reactivity of these materials is affected by these variables. In conclusion, there is a broad range of reducible perovskite oxides, providing opportunities to tune their performance in chemical looping applications.