![Sample our Physical Sciences journals, sign in here to start your FREE access for 14 days]({"type":"image" , "src" : "/sda/110819/TOC-Subject-Sample-2021-Physical-Sciences.jpg"})
abstract
Brillouin spectra and generation of the second optical harmonic in a series of SBN-x crystals with different chemical compositions are investigated in the 115–850 K temperature range. The integral intensity of the second harmonic signal follows the Arrhenius law with activation energies of ΔU = 0.09–0.3 eV. The second harmonic generation (SHG) is observed in paraelectric phase of the SBN-x crystals, revealing the presence of polar regions in the paraelectric phase. The spectral width of the SHG spectrum does not exceed 0.3 cm−1 and is temperature independent. Upper limit of the spectral width of the SHG spectrum provides lower limit of the lifetimes of polar regions, which are longer than 15 ps. It suggests that the doubled frequency signal in the paraelectric phase of the SBN-x crystals is generated in areas with lifetimes longer than 15 ps. It is shown that local polar regions cannot explain the anomalies of the elastic module near the ferroelectric phase transition in SBN-x.
Acknowledgements
This work was supported by the state assignment no. AAAA-A17-117052410033-9, the Russian Foundation for Basic Research, projects no. 18-02-00399 and 17-32-50090. Some part of the experiments was performed in the multiple-access center “High-Resolution Spectroscopy of Gases and Condensed Matter” in IA&E SBRAS (Novosibirsk, Russia). Growth experiments was supported by the Volkswagen Foundation Az.: 90 261 of 29th February 2017.