Kinetic control of A-site cation disorder and its impact on the ferroelectric phase transition in La2SrSc2O7 layered perovskite oxide

Abstract

We demonstrate a strategy for tuning the Curie temperature (TC) of hybrid improper ferroelectric La2SrSc2O7, an n = 2 Ruddlesden–Popper-type perovskite oxide. By kinetically controlling the distribution of A-site cations (La/Sr) through different post-sintering cooling rates, TC can be varied widely from ∼400 to ∼700 K. Structural mode analysis reveals that increasing A-site cation disorder weakens ScO6 octahedral deformation and enhances octahedral rotation, thereby stabilizing the polar phase and leading to a higher TC. A linear correlation between TC and A-site cation disorder is established, highlighting A-site cation disorder as a key descriptor for tailoring ferroelectricity in La2SrSc2O7. Consequently, controlling the cooling rate provides an effective, composition-independent pathway for designing hybrid improper ferroelectrics with tunable functionalities, offering a distinct alternative to conventional compositional design.