Properties of unconventional lithium bismuthate glasses

Unconventional bismuthate glasses containing lithium oxide have been prepared by a conventional melt-quench technique. X-ray diffraction, scanning electron microscopy, and differential thermal analysis show that stable binary glasses of composition $x{\mathrm{Li}}_2\mathrm{O}-(100-x)\mathrm{}{\mathrm{Bi}}_2{\mathrm{O}}_3$ can be achieved for $x=20\mathrm{}–35$ mol %. Systematic variation of the glass-transition temperature, density, and molar volume observed in these glasses indicates no significant structural change with composition. Differential thermal analysis and optical studies show that the strength of the glass network decreases with the increase of ${\mathrm{Li}}_2\mathrm{O}$ content in the glass matrix with a small deviation for the extra stable $30{\mathrm{Li}}_2{\mathrm{O}-70\mathrm{Bi}}_2{\mathrm{O}}_3$ glass composition. Studies of Raman spectra and molar volume ensure that all glasses are built up of $\left[{\mathrm{BiO}}_6\right]$ octahedral units, while the influence of ${\mathrm{Li}}^{+}$ ions in the glass matrix is also confirmed from optical, Raman, and electrical studies. Wide transmitting window in the optical region having sharp cutoffs in both ultraviolet-visible and infrared regimes may make these glasses useful in spectral devices. High dielectric values in these glasses compared to glasses formed with conventional glass former can be attributed to the influence of the high polarizability of the unconventional network forming cations, ${\mathrm{Bi}}^{3+}.$