Phase transition in Cs₃Bi₂I₉ ferroelastic: investigation by Raman scattering technique

• Дата: 2005
• Автори: Motsnyi, F.V., Vuychik, M.V., Smolanka, O.M., Peresh, E.Yu.
• Формат: Стаття
• Мова: English
• Опубліковано: НТК «Інститут монокристалів» НАН України 2005
• Назва видання: Functional Materials
• Онлайн доступ: http://dspace.nbuv.gov.ua/handle/123456789/137644
• Назва журналу: Digital Library of Periodicals of National Academy of Sciences of Ukraine
• Цитувати: Phase transition in Cs₃Bi₂I₉ ferroelastic: investigation by Raman scattering technique / F.V.Motsnyi, M.V.Vuychik, O.M.Smolanka, E.Yu.Peresh // Functional Materials. — 2005. — Т. 12, № 3. — С. 491-496. — Бібліогр.: 20 назв. — англ.

Raman scattering in unpolarized light has been studied for the first time for Cs₃Bi₂I₉ layered ferroelastic at temperatures from 5 to 300 К in the heating mode. Neither soft mode nor frequency softening was observed. For the low-frequency lines 37.0, 45.0, 61.4, 68.3 and 97.4 cm⁻¹, the doublets were detected. Those may be due to Davydov splitting or splitting of degenerate vibrations of E-symmetry. The intensity equalization effect has been found for 114.8 and 125.3 cm⁻¹ lines in the phase transition region. It is shown that the 150.6 and 131.2 cm⁻¹ lines can be explained by vibrations of Bi⁻¹ bonds in the [Bi1]³⁻ octahedrons. The Raman spectra in z(y,y)z and z(y,x)z polarizations taken at 100 К were found to be similar to those in unpolarized light. An analysis of both known and our results enabled us to conclude that the ferroelastic phase transition at Тᶜ = 220 К belongs to those of the first order but close to the second one.