Perovskite ferroelectrics play an essential role in modern science and technology. The excellent properties of perovskites are closely related to their lattice dynamics. Potassium tantalate niobate (KTaNbO, abbreviated as KTN) is a typical solid-solution perovskite with superior properties. Although the optical and electrical performances of KTN crystals have been widely explored, information on their lattice dynamics is still scarce, which partially limits the research and performance optimization of KTN. As a solid-solution, spontaneous polarization of KTN exhibits strong tunability, and there is stress within KTN. Here, we performed first-principles calculations in conjunction with experiments to investigate the polarization- and stress-related lattice dynamics in KTN. We assigned the vibration modes of observed Raman peaks, and established the relationship between spontaneous polarization and vibration. Especially, the lattice dynamics evolution of KTN crystal under stress was investigated. And the results provide insights into the regulatory effect of stress on dielectric property from the perspective of lattice dynamics. Finally, the variation trends of phonons under stress, as well as the mechanism of stress effect in tetragonal perovskites were explained. The conclusions drawn for KTN crystal were generalized to tetragonal ferroelectric systems. Our results help to reflect spontaneous polarization and structural characteristics distribution through non-destructive Raman spectra, and give a reference for improving performance by regulating lattice dynamics. The findings will hopefully guide research on performance origin and refined design of perovskite functional materials.

中文翻译：

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固溶体钙钛矿铁电体中与极化和应力相关的晶格动力学


钙钛矿铁电体在现代科学技术中发挥着重要作用。钙钛矿的优异性能与其晶格动力学密切相关。钽酸铌酸钾（KTaNbO，简称KTN）是一种典型的固溶体钙钛矿，具有优越的性能。尽管KTN晶体的光学和电学性能已被广泛探索，但其晶格动力学信息仍然匮乏，这在一定程度上限制了KTN的研究和性能优化。作为固溶体，KTN的自发极化表现出很强的可调性，并且KTN内部存在应力。在这里，我们结合实验进行了第一性原理计算，以研究 KTN 中与极化和应力相关的晶格动力学。我们指定了观察到的拉曼峰的振动模式，并建立了自发极化和振动之间的关系。特别是，研究了 KTN 晶体在应力作用下的晶格动力学演化。研究结果从晶格动力学的角度揭示了应力对介电性能的调节作用。最后，解释了四方钙钛矿中声子在应力作用下的变化趋势以及应力效应的机制。对 KTN 晶体得出的结论被推广到四方铁电系统。我们的研究结果有助于通过无损拉曼光谱反映自发极化和结构特征分布，并为通过调节晶格动力学来提高性能提供参考。这些发现有望指导钙钛矿功能材料的性能起源和精细设计研究。