Empirical Modeling of B-site Ordered Perovskites

Complex perovskites of the form AB0.5B’0.5X3, where A, B, and B’ are cations and X is an anion, abound in technological applications. In most cases B and B’ cations chemically order on crystallographically unique sites, influencing properties and resulting in a volume shrinkage. In this work, various compounds including (Sr0.5Ba0.5)(Mg0.5W0.5)O3 and (Ca0.5Sr0.5)(Mg0.5W0.5)O3, K0.5La0.5TiO3 as well as several compositions in the [(Ca, Sr, Ba)1‑3xLa2x](Mg0.5W0.5)O3 and K(1-3x)/2La(1+x)/2TiO3 series were made via conventional techniques. In particular, the [(Ca, Sr, Ba)1‑3xLa2x](Mg0.5W0.5)O3 system allows the effect of A cation size on B-site shrinkage to be studied as a function of A cation size as the host crystal changes from cubic (A=Ba) to tetragonal (A=Sr) to monoclinic (A=Ca). Data mining was also employed to include the host of other reported ordered perovskites in a model for the prediction of the B-site shrinkage, DrB. Such a model would allow the prediction of structures with little or no experimental data, thus eliminating much of the trial and error and drastically reducing material-development time and costs. The goal of this project is to establish a generic numerical model for the effective ionic radii and lattice constants for complex perovskites containing B-site ordering.