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Crystal Structure and the Spectral Response of the Ba‐Doped SrTiO 3 Incipient Ferroelectrics
Author(s) -
Linnik Ekaterina D.,
Lukyanchuk Igor A.,
Mikheykin Alexey S.,
Ragulya Andrey V.,
Gorshunov Boris P.,
Alyabyeva Liudmila N.,
Zhukov Sergey S.,
Mezzane Daoud,
Razumnaya Anna G.
Publication year - 2021
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.202100010
Subject(s) - raman spectroscopy , dielectric , ferroelectricity , materials science , tetragonal crystal system , condensed matter physics , phonon , phase transition , soft modes , curie temperature , atmospheric temperature range , polar , crystal structure , crystallography , chemistry , optics , physics , optoelectronics , ferromagnetism , meteorology , astronomy
The crystal structure and lattice dynamics of quantum paraelectric Ba x Sr 1− x TiO 3 ( x = 0, 0.01, 0.02) solid solutions are studied using X‐ray diffraction (XRD), Raman and terahertz‐infrared (THz‐IR) spectroscopies in a temperature range of 4–300 K. XRD and Raman spectroscopy reveal the cubic‐to‐tetragonal nonpolar structural phase transition at about 100 K. At the same time, Raman spectra manifest the presence of polar modes, TO 2 and TO 4 , normally prohibited in paraelectric phase. Emergence of these modes indicates the appearance of the polar nanoregions in a broad temperature range. The modes become more intensive at low temperatures, and temperature dependence of their intensities on cooling reveals the kink‐like change of the slope from flat to steep, indicating on activation of polar nanoregions. The transmission THz‐IR spectra show that squared frequency of the polar TO 1 soft mode, responsible for ferroelectric transition, follows Cochran's behavior at high temperatures. However, at low temperatures, it doesn't vanish at extrapolated Curie temperature but saturates, demonstrating the plateau feature below 20 K. This behavior, coherent with known saturation of the dielectric constant, indicates that transition to ferroelectric phase in Ba x Sr 1− x TiO 3 is suppressed by quantum fluctuations and the system stays in quantum paraelectric state at very low temperatures.