Temperature-dependent Raman scattering study on Cs4W11O35 and Rb4W11O35 systems

In this work we report results of Raman scattering study on Cs4W11O35 and Rb4W11O35 in the 30–295 K temperature range. Changes in the Raman spectra indicated presence of two structural phase transformations in the Cs4W11O35 (Rb4W11O35) system taking place at 110 K (100 K) and 165 K (210 K). These transformations lead to symmetry increase on cooling. Temperature dependence of Raman linewidths indicated larger contribution of an orientational mechanism in Cs4W11O35 than in the Rb4W11O35 system. No soft-like mode was observed that could point to a displacive type behavior at the phase transitions. Additional Raman scattering measurements were performed on the Cs4W11O35 system in the 300–820 K range. No temperature-induced phase transitions were observed for this system above room temperature.

Graphical abstractValence Balanced Hexagonal Bronzes obtained by partial substitution of the tungsten atoms in the AxWO3 structure by atoms with lower valence state. These materials undergo a number of phase transitions and display ferroelectric or anti-ferroelectric properties associated with reversible dipole orientations arising from displacements of tungsten atoms from the center of the WO6 octahedral units. In the present work we report mainly results of temperature Raman scattering experiment on Cs4W11O35 and Rb4W11O35 hexatungstates in the 30–295 K temperature range.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We report results of temperature Raman scattering experiment on Cs4W11O35 and Rb4W11O35 hexatungstates in the 30–295 K temperature range. ► These materials exhibit probably two temperature-induced phase transitions at low temperatures. ► These transformations lead to symmetry increase on cooling. ► Damping effect present larger contribution of orientational mechanism in CW than in the RW system.