The study of short- and medium-range order in oxyfluoroniobate glasses

• The glasses are obtained in the NbO2F-BaF2-ZnF2-BiF3 and MnNbOF5-BaF2-BiF3 systems.
• The studies of Raman spectra and sound velocities are performed for the glasses.
• The nanometer heterogeneity sizes are calculated for the glasses based on NbO2F.
• The high- and low-frequency Raman spectra are used for analysis of crystallization.
• This approach allowed obtain information on the processes of glass crystallization.

The present work illustrates the perspective of using the analysis of high- and low-frequency Raman in the study of oxyfluoride glasses in the NbO2F-BaF2-ZnF2-BiF3 and MnNbOF5-BaF2-BiF3 systems. The article examines two aspects for these glasses: the structure and crystallization. The use of these approaches revealed that the glass networks of NbO2F-BaF2-ZnF2-BiF3 series are built from the clusters consisting of NbO3F3 polyhedra connected by oxygen bridges and have a virtually equal scale of nanosized heterogeneity, which is not greatly affected by modifying components (ZnF2 and BiF3) as the medium-range-order is formed mainly as clusters of glass-forming polyhedra. The analysis of high- and low-frequency ranges of Raman spectra of glasses in the MnNbOF5-BaF2-BiF3 system allowed controlling the emergence of crystalline phases in glass, beginning of destruction of the oxyfluoroniobate network and understands the processes occurring during crystallization.