Empirical Modeling of B-site Ordered Perovskites

Complex perovskites of the form AB _0.5 B’ _0.5 X ₃ , 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 (Sr _0.5 Ba _0.5 )(Mg _0.5 W _0.5 )O ₃ and (Ca _0.5 Sr _0.5 )(Mg _0.5 W _0.5 )O ₃ , K _0.5 La _0.5 TiO ₃ as well as several compositions in the [(Ca, Sr, Ba) _{1‑3 x} La _{2 x} ](Mg _0.5 W _0.5 )O ₃ and K _{(1-3 x )/2} La _{(1+ x )/2} TiO ₃ series were made via conventional techniques. In particular, the [(Ca, Sr, Ba) _{1‑3 x} La _{2 x} ](Mg _0.5 W _0.5 )O ₃ 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, D r _B . 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.