Structure and ion mobility in glasses in the BiF3–PbF2–ZrF4 systems studied by Raman and NMR spectroscopy

Abstract

The structure and ion mobility in glasses in the PbF2–BiF3–ZrF4 ternary systems have been studied by Raman and 19F NMR spectroscopy. Raman spectra of glasses of compositions with concentration ZrF4>45% remain typical for fluorozirconate glasses and zirconium complex fluorides. The correlation between the vibrational data and the n(F)/n(Zr+Bi) ratio in glasses is identified. The glass network in the BiF3–PbF2–ZrF4 system is formed according to the zirconium complex fluorides structural regularities. The Zr nearest surrounding and the glass network polymerization degree depend on the nF/n(Zr+Bi) ratio. One can affirm that the coordination number of Zr atom is equal to 7–8. BiF3 completely loses its individual crystal geometry in the structure of glasses under study: it serves as an ‘intermediate’, providing the glass stability at ZrF4 concentrations up to 40mol%. For the investigated glasses n(F)/n(Zr+Bi) ratio is between 5 and 4. Found that with temperature increasing (150→550K) in the fluorine subsystem of the glasses the transition is observed from a rigid lattice to diffusion through an intermediate phase associated with an appearance of local motions of zirconium fluorine-containing groups that form the glass network. Examined the correlation between the temperature at which this transition occurs, and the concentration of fluoride in the glass composition is included.