Crystal Structure and the Spectral Response of the Ba‐Doped SrTiO3 Incipient Ferroelectrics. Issue 7 (29th April 2021)

• Record Type: Journal Article
• Authors: 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.
• Is Part Of: Physica status solidi. Volume 258:Issue 7(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-04-29
• Subjects: crystal structures -- lattice dynamics -- quantum paraelectrics -- strontium titanate -- vibrational spectroscopy; Solid state physics -- Periodicals; Solids -- Periodicals; Atomic structure -- Periodicals; 530.41
• DOI: 10.1002/pssb.202100010
• Languages: English
• ISSNs: 0370-1972

Abstract

Abstract : The crystal structure and lattice dynamics of quantum paraelectric Ba x Sr1− x TiO3 ( 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, TO2 and TO4, 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 TO1 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 Sr1− x TiO3 is suppressed by quantum fluctuations and the system stays in quantum paraelectric state at very low temperatures. Abstract : Crystal structure and lattice dynamics of quantum paraelectric Ba x Sr1− x TiO3 are studied at temperatures 4–300 K. Polar nanoclusters appear in a broad temperature range and extend with increasing concentration of Ba ions. Clusters' activation locally stabilizes the ferroelectric phase and reduces the temperature of structural transition. Quantum fluctuations suppress the ferroelectric state, conserving the paraelectric state at very low temperatures.