Inelastic light scattering studies of diffuse phase transition in ferroelectric Sr_1.9Ca_0.1NaNb₅O₁₅ thin films

Abstract

The dynamic behavior of highly oriented ferroelectric Sr 1.9 Ca 0.1 NaNb 5 O 15 thin films has been investigated by Brillouin light scattering over a wide temperature range between 25 and 450 • C. The temperature variations of the full-width at half-maximum (FWHM) of the central peak (CP) are found to exhibit marked changes around the Curie temperature (T c = 246 • C). The CP reveals a relaxational mode behavior, which is attributed to thermally activated fast relaxation of polar nanoregions (PNRs). The width of the CP decreases steadily upon cooling from ∼400 • C to T c and shows little subsequent change within the ferroelectric state, indicating an increase of the number of PNRs and a slowing down of their dynamics. By using a modified superparaelectric model, the activation energy (H 0 ) of the relaxation processes and the Burns temperature (T B ) are determined to be 2939 and 385 • C, respectively. The evidence for this diffuse phase transition provided by Brillouin scattering is in agreement with results obtained from the temperature-dependent dielectric permittivity, refractive index, and Raman spectra.

Recent advances in linear and nonlinear Raman spectroscopy. Part VII

“…Lin and Cheng described the use of hot‐stage microscopy and thermal MRS in the study of phase transformation of metoclopramide HCl monohydrate . Liu and co‐workers studied diffuse phase transition in ferroelectric Sr 1.9 Ca 0.1 NaNb 5 O 15 thin films using inelastic light scattering …”

Study of Structural and Dielectrical Properties of Lead Free Polycrystalline Electro Ceramics Ba<SUB>5</SUB>CaTi<SUB>2</SUB>Nb<SUB>8</SUB>O<SUB>30</SUB> (BCTN) for Microwave Tunable Device Applications

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