Abstract:
Raman spectra of potassium dihydrogen phosphate crystals near the order-disorder phase transition temperature are measured. During the analysis, the temperature dependences of the spectral line parameters are compared with the known calculation data on the dispersion of optical phonons, on which Raman scattering occurs. As a result of the analysis, an assumption is made that in the region of the phase transition temperature there is a temperature region when both phases coexist in the crystal. The ferroelectric phase, when cooled below the phase transition temperature, appears in the form of nanometer-sized clusters and, upon further cooling of the sample, fills the entire space due to an increase in the cluster size. The estimates made on the basis of the known phonon confinment model show that in the range of about 10$^\circ$C from the phase transition temperature, the size of the model cluster increases from zero to about 20 nm.
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