Incipient Ferroelectric Properties of NaTaO₃

Abstract

Microwave dielectric permittivity of NaTaO₃ ceramics exhibits increase on cooling and saturation at low temperatures, which is typical for incipient ferroelectrics. The temperature dependence of permittivity was successfully fit with the Barrett formula and explained by polar phonon softening detected in infrared reflectivity and THz transmision spectra. Solid solution of NaTaO₃ with Na_0.5Bi_0.5TiO₃ (NBT) exhibits increase of both permittivity and dielectric loss with rising Na_0.5Bi_0.5TiO₃ concentration. This is caused by increasing contribution of dielectric relaxation seen in THz dielectric spectra below phonon frequencies. The relaxation stems from dynamics of polar nanoclusters and ferroelectric domains in NBT.

Keywords:

• Incipient ferroelectricity
• infrared and THz spectroscopy
• phonons
• microwave ceramics

Acknowledgments

This work was supported by the Czech Science Foundation (Project 202/09/0682) and AVOZ 10100520.