Stabilizing ferroelectricity in alkaline‐earth‐metal‐based perovskites (ABO3) via A‐ (Ca2+/Sr2+/Ba2+) and B‐site (Ti4+) cationic radius ratio (RA/RB)

Various distortion parameters for alkaline‐earth‐metal‐based perovskites (A2+B4+O3) have been analyzed as a function of A‐ and B‐site cationic radii RA and RB. The observed octahedral rotations and their associated mode amplitudes have shown an increasing trend with larger B‐site cations, while a decreasing trend has been observed with larger A‐site cations. Moreover, the analysis demonstrates that for incipient ferroelectrics like CaTiO3 and SrTiO3, having respective space groups Pnma (a−0b+0a−0) and Pm3m (a00a00a00), ferroelectric displacements are achieved via cation manipulation, which is governed by the RA/RB parameter. The increase in RA/RB through substitutions on the A site may suppress octahedral rotations as well as A‐site anti‐polar displacements in CaTiO3 and can consequently lead to a ferroelectrically distorted BaTiO3‐like P4mm (a00a00c0+) phase via a cubic phase of SrTiO3, which has an intermediate RA/RB parameter. These results have been further corroborated by the calculated amplitudes of various frozen phonon modes associated with the cubic Pm3m Brillouin zone, responsible for symmetry breaking to tilt‐oriented non‐ferroelectric Pnma and ferroelectric P4mm phases. This study establishes the structure–property correlation that eases the initial optimization process for various alkaline‐earth‐metal‐based perovskites.