Terahertz and infrared studies of antiferroelectric phase transition in multiferroic Bi 0.85 Nd 0.15 FeO 3

• Published in: Journal of applied physics 2011-10, Vol.110 (7), p.074112-074112-7
• Main Authors: Goian, V., Kamba, S., Greicius, S., Nuzhnyy, D., Karimi, S., Reaney, I. M.
• Format: Article
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.3650241

High-frequency dielectric studies of Bi 0.85 Nd 0.15 FeO 3 ceramics performed betweeen 100 and 900 K reveal hardening of most polar phonons on cooling below antiferroelectric phase transition, which occurs near 600 K. Moreover, a strong THz dielectric relaxation is seen in paraelectric phase. Its relaxation frequency softens on cooling towards T C ≈ 600 K, its dielectric strength simultaneously decreases, and finally the relaxation disappears from the spectra below 450 K. Both phonon and dielectric relaxation behavior are responsible for a decrease in the dielectric permittivity at the antiferroelectric phase transition. Origin of unusual strong THz dielectric relaxation in paraelectric phase is discussed. Bi 0.85 Nd 0.15 FeO 3 structure lies on the phase boundary between polar rhombohedral and non-polar orthorhombic phase and owing to this, the polarization rotation and polarization extension can enhance the piezoelectric response of this system. Similarities and discrepancies with lead-based piezoelectric perovskites, exhibiting morphotrophic phase boundary between two ferroelectric phases, are discussed.