Ferroelectricity vs Antiferroelectricity in n = 2 Ruddlesden–Popper Phases

Ferroelectric materials – those with a spontaneous, switchable electric polarization – find application in a wide range of electronic devices. We are investigating a new class of ferroelectric materials, the hybrid improper ferroelectrics, which gain their electric polarization through subtle structural distortions. We have observed that while LiSrTa2O7 adopts an improper ferroelectric structure down to the lowest temperatures measured (5 K), the closely related phase Li2SrNb2O7 switches from an improper ferroelectric to proper ferroelectric structure at low temperature. To better understand the competition between the proper and improper ferroelectric states and how the composition of materials favours one or the other, we have prepared a series of related materials and wish to collect high-resolution neutron powder diffraction data to determine their structures.

铁电材料（Ferroelectric materials）—— 指具有自发且可切换电极化特性的材料 —— 广泛应用于各类电子器件中。我们正在研究一类新型铁电材料——混合型非本征铁电体（hybrid improper ferroelectrics），其电极化源于细微的结构畸变。我们观察到，LiSrTa₂O₇在低至所测最低温度（5 K）时仍保持非本征铁电结构（improper ferroelectric structure），而与其密切相关的物相Li₂SrNb₂O₇则会在低温下从非本征铁电结构转变为本征铁电结构（proper ferroelectric structure）。为了深入理解本征与非本征铁电态之间的竞争关系，以及材料组成如何倾向于其中某一状态，我们制备了一系列相关材料，并希望采集高分辨率中子粉末衍射数据（high-resolution neutron powder diffraction data）以确定其结构。