Glass transition and composite formation in InF₃-containing oxyfluoroniobate system

The glasses in the system MnNbOF₅-BaF₂-InF₃ have been firstly synthesized and studied. The thermal parameters of these glasses are analyzed. It was stated that glass of the composition 40MnNbOF₅-40BaF₂-20InF₃ is the most thermal stable in the system under study. By X-ray analysis the compositions of the crystalline phases obtained at the glass thermal treatment were determined: the main phases are Ba₃In₂F₁₂ and BaNbOF₅. By Raman and IR spectra analysis it was stated that the networks of glasses in the system are built by the structural type of the glasses in NbO₂F-BaF₂ system: (NbO_nF_m) polyhedra joined oxygen bridges. Indium trifluoride forms InF₆ polyhedra, which are embeded between oxyfluoroniobate ions, forming a common networks or forms its own layers from InF₆ polyhedra. IR-spectroscopy method showed that at devitrification of the sample 30MnNbOF₅-50BaF₂-20InF₃ the band position and shape change in going from glass state to crystalline. The bands in the range 900–700 cm⁻¹ shift into the low-frequency range and transformed into narrow peaks characteristic for the crystalline state. It was determined that for this sample the IR-spectroscopy method fixes the presence of the crystalline phases at 340°C without time of exposure, despite the fact that X-ray analysis shows an amorphous state for this sample at the same temperature. It was suggested, that controlling the composition and conditions of annealing of the glasses it can be obtain the transparent glass-ceramics of definite composition.