Structural transformations in a single‐crystal Rb₂NaYF₆: Raman scattering study

Abstract

This paper reports Raman spectroscopy investigation of phase transitions in Rb2NaYF6 crystal. The experimental spectra were compared with the calculated one. The spectra were obtained in temperature range from 8 to 300 K. The Raman spectra shows anomalous temperature‐dependent behavior at T1 = 154 and T2 = 122 K. Soft mode restoration has been found, which allows us to attribute first transition at 154 K to displacive type. Detailed analysis temperature dependencies of the line positions and widths have been performed. We found no effects of possible lattice disorder anywhere, except narrow (about 20 K) range above the T1 temperature. The Raman spectra of Rb2NaYF6 crystal have been obtained and analyzed under hydrostatic pressure up to 4.33 GPa (at T = 295 K). The high pressure experiment up to 4.33 GPa did not disclose any effects associated with phase transitions. The lattice vibration spectra were calculated up to 10 GPa. The calculation has been demonstrated that the Rb2NaYF6 does not undergo high pressure phase transition. Copyright © 2013 John Wiley & Sons, Ltd.

Microwave sol–gel synthesis and upconversion photoluminescence properties of CaGd2(WO4)4:Er3+/Yb3+ phosphors with incommensurately modulated structure

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