Combinatorial screening of the crystal structure in Ba–Sr–Mn–Ce perovskite oxides with ABO3 stoichiometry

Abstract

ABO₃ oxides with perovskite-related structures are attracting significant interest due to their promising physical and chemical properties for many applications requiring tunable chemistry, including fuel cells, catalysis, and electrochemical water splitting. Here we report on the crystal structure of the entire family of perovskite oxides with ABO₃ stoichiometry, where A and B are Ba, Sr, Mn, and Ce. Given the vast size of this chemically complex material system, exploration for stable perovskite-related structures with respect to their constituent elements and annealing temperature is performed by combinatorial pulsed laser deposition and spatially resolved characterization of the composition and structure. As a result of this high-throughput experimental study, we identify hexagonal perovskite-related polytypic transformation as a function of composition in Ba_1−xSr_xMnO₃ oxides after annealing at different temperatures. Furthermore, a hexagonal perovskite-related polytype is observed in a narrow composition–temperature range of BaCe_xMn_1−xO₃ oxides. In contrast, a tetragonally distorted perovskite is observed across a wider range of chemical compositions and annealing temperatures in Sr_1−xCe_xMnO₃ oxides. This structural stability is further enhanced along the BaCe_xMn_1−xO₃–Sr_1−xCe_xMnO₃ pseudo-binary tie line at x = 0.25 by increasing Ba incorporation and annealing temperature. These results indicate that BaCe_xMn_1−xO₃–Sr_1−xCe_xMnO₃ pseudo-binary oxide alloys (solid solutions) with a tetragonal perovskite structure and broad composition–temperature range of stability are promising candidates for thermochemical water splitting applications.