Raman spectroscopic studies on the ferroelectric soft mode in Sn_xSr_1-xTiO₃

ABSTRACT

The Raman spectra of novel ferroelectric ceramics Sn_xSr_1-xTiO₃ (x = 0.1, 0.05 and 0.02) were obtained to clarify the mechanism of their ferroelectric phase transitions. Two transverse-optic modes in the ferroelectric phase showed softening toward the ferroelectric transition temperature. A comparison of the spectra obtained for Sn_xSr_1-xTiO₃ with the spectrum of Pb_xSr_1-xTiO₃ facilitated the assignment of the observed modes under the assumption of the ferroelectric phase in $C_{4v}^1$ symmetry. However, several peaks violating the Raman selection rules were observed, suggesting the emergence and growth of polar regions even in the paraelectric phase.

KEYWORDS:

• Ferroelectricity
• Raman scattering
• Sn_xSr_1-xTiO₃

Acknowledgments

Authors are grateful to Dr. S. Suzuki and Dr. A. Ando at Murata Manufacturing Co. Ltd. for providing us SSTO and PSTO samples and for stimulating discussions. T. N. thanks Assoc. Prof. T. Nezu at Health Science University of Hokkaido (HSUH) for his support in arranging experimental equipment. Parts of the experiments were performed at the High-Tech research center at HSUH.