Hybrid improper ferroelectrics (HIFs) have been studied intensively over the past few years to gain an understanding of their temperature-induced phase transitions and ferroelectric switching pathways. Here we report a switching from a first- to a second-order phase transition pathway for HIFs Ca3−xSrxTi2O7, which is driven by the differing entropies of the phases that we identify as being associated with the dynamic motion of octahedral tilts and rotations. A greater understanding of the transition pathways in this class of layered perovskites, which host many physical properties that are coupled to specific symmetries and octahedral rotation and tilt distortions—such as superconductivity, negative thermal expansion, fast ion conductivity, ferroelectricity, among others—is a crucial step in creating novel functional materials by design.
From first- to second-order phase transitions in hybrid improper ferroelectrics through entropy stabilization
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By Mark | Comments are ClosedAblitt C, Mostofi AA, Bristowe NC and Senn MS (2018) Control of Uniaxial Negative Thermal Expansion in Layered Perovskites by Tuning Layer Thickness. Front. Chem. 6:455. doi: 10.3389/fchem.2018.00455 Uniaxial negative thermal expansion (NTE) is known to occur in low $n$Read more
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