Crystallization of tungstenbronze-type Ba₂NaNb₅O ₁₅ in high-Nb₂O₅-content glass: An inelastic light scattering study

In situ observations of phonon Raman and Boson scattering were performed in high- Nb₂O₅ -content barium-sodium aluminophosphate glass, which crystallizes tungstenbronze-type Ba₂NaNb ₅O₁₅ (BNN), during heating and subsequent cooling processes in order to examine the BNN crystallization dynamics and phase transitions. It is suggested that NbO₆ clusters/cohesive regions are present and are subjected to stress by the surrounding aluminophosphate network prior to crystallization of the BNN phase. Furthermore, in the cooling period, a successive phase transition (4/mmm→4mm→mm2) of the BNN phase was observed in the glass-ceramics, implying the possibility of producing functional glass-ceramics with ferroelastic properties.