H. -R. Xia, L. -X. Li, J. -Y. Wang, Y. -G. Liu, J. -Q. Wei: Soft-Mode Spectroscopy in Fe:KTa1-xNbxO3 Crystals

Crystal Research and Technology

Cryst. Res. Technol. 35 (2000) 1209 - Abstract -

H. -R. Xia, L. -X. Li, J. -Y. Wang, Y. -G. Liu, J. -Q. Wei

Department of Physics, Environmental Engineering Department, and National Laboratory of Crystal Materials, Shandong University, Jinan, People's Republic of China

Soft-Mode Spectroscopy in Fe:KTa_1-xNb_xO₃ Crystals

Fe-doped potassium tantalite niobate, Fe:KTa_1-xNb_xO₃ (Fe:KTN), crystallizes with x = 0.48 and a perovskite-type structure in tetragonal system with point group 4mm, conforming space group P4mm. The paraelectric-ferroelectric structural transition of the Fe:KTN is studied by Raman scattering investigations. A condensed soft lattice vibrational mode at the phase transition has been analyzed. It originates from the symmetric O2/O3-Nb/Ta-O3/O2 in-plane bending of the Nb/TaO₆ group. The soft optical phonon mode concerns the extraordinary transverse optical phonons propagating along the [110] direction. The Raman spectra measured reflect the crystal disorder. Curie temperature measured by two methods is within 353 and 356.5 K.

Keywords: structural phase transition, soft lattice vibrational mode, Raman scattering

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