First-order hybrid improper ferroelectric phase transition in (Sr,Ca)3Sn2O7 ceramics

Reference Presenter Authors
(Institution)
Abstract
08-083 Xiao Qiang Liu Liu, X.(Zhejiang University); Lu, J.(Zhejiang University); Chen, X.(Zhejiang University);      Improper ferroelectricity has been attracted many attentions because of its potential application in creating room temperature multiferroicity with strong magnetoelectric coupling. Recently, the hybrid improper ferroelectricity (HIF) has been proposed by the first-principle calculation, and the ferroelectricity is induced by a complex distortion pattern consisting of two oxygen octahedron tilting modes, such as a-a-c0 and a0a0c+ (in Glazer's notation) in perovskite [1]. The HIF should widely exist in the perovskites and layered perovskites since the oxygen octahedron rotations are ubiquitous distortions in the perovskite-related materials.
     In the present work, the experimental evidences of HIF in Ruddlesden-Popper (Sr,Ca)3Sn2O7 ceramics have been shown. The room temperature ferroelectric hysteresis loops are observed in these ceramics, and a polar orthorhombic structure with two oxygen tilting modes has been confirmed by the X-ray powder diffraction. A first-order improper ferroelectric phase transition was evidenced by the temperature-dependence of dielectric constant, and the Curie temperature increases linearly with increasing of the contents of Ca2+ ions. 
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