In the present work, the crystal structure, ferroelectric and dielectric properties of the dense single-phase Li₂CaTa₂O₇ ceramics with A-site ordered double-layer Ruddlesden-Popper structures have been investigated by the experiments and first-principles calculations. A polar Pna2₁ phase was determined by the Rietveld refinement against the X-ray diffraction pattern at room temperature, and it was confirmed by its lowest calculated energy and rigid phonon modes. The ferroelectricity was found by observing the ferroelectric hysteresis loop at room temperature, and its remanent polarization was similar to the value calculated from the Berry phase and Born effective charge approaches. The ferroelectricity is a non-conventional proper one since its polarization is induced from the displacement of oxygen anions instead of tantalum cations based on the individual atomic polarization. A first-order transition from an antiferroelectric to paraelectric phase around 900 K was found by the DSC and variable-temperature dielectric measurements. From the present work, the room-temperature ferroelectricity is experimental confirmed in the present ceramics, inspiring the search for new ferroelectricity in the ceramics with A-site ordered Ruddlesden-Popper structures.

在本工作中，通过实验和第一性原理计算，研究了具有A-位有序双层Ruddlesden-Popper结构的致密单相Li ₂ CaTa ₂ O ₇陶瓷的晶体结构，铁电和介电性能。极地Pna 2 ₁在室温下，通过Rietveld细化对X射线衍射图谱确定了相，并由其最低的计算能量和刚性声子模态证实了这一点。通过在室温下观察铁电磁滞回线来发现铁电，其剩余极化强度类似于从Berry相和Born有效电荷法计算得出的值。铁电是一种非常规的合适的铁电，因为其极化是基于单个原子极化由氧阴离子而不是钽阳离子的置换引起的。通过DSC和可变温度电介质测量发现了从反铁电相到顺电相在900 K附近的一阶跃迁。从目前的工作来看，一个上门订购Ruddlesden -波普尔结构。