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.