Empirical models for layered A‐site ordering in perovskite titanates

Abstract

AbstractIn industry and labs, predictive models describing processing‐structure relationships are inherently valuable, yet few exist for cation ordering in perovskites. In this work, 15 compositions in the [(NayLi1−y)(1−3x)/2La(1+x)/2]TiO3 (NLLT) system (y = 0.25, 0.5, and 0.75; x = 0, 0.0533, 0.1, 0.1733, and 0.225) were synthesized using a conventional solid‐state mixed‐oxide method. X‐ray diffraction data show that some degree of long‐range ordering of A‐site cations exists for x ≥ 0.1, although electron‐diffraction data indicate that short‐range ordering exists even for x < 0.1, with the degree of ordering decreasing as the value of x increases. Empirical models have been derived for the A‐site ordering parameter (η) as well as the resultant expansion (ΔrA) for each y series in the NLLT system, from which two general models were derived for perovskites with any arbitrary degree of 1:1 layered A‐site ordering. These general models allow for the prediction of the order parameter and resulting expansion using only published ionic radii data.