Thermal behavior, FT-IR spectroscopy and water durability of Li_2O–PbO–ZnO–P_2O_5 glasses

Lithium–lead–zinc phosphate glasses having a composition (35-y)Li₂O–yPbO–15ZnO– 50P₂O₅ (0≤y≤35 mol%) were prepared by using the melt–quench technique. Their structures have been characterized by infrared spectroscopy. The substitution of 15 mol% ZnO and 35 mol% PbO for 50 mol% Li₂O in the binary 50Li₂O–50P₂O₅ glass decreases the molar volume (ΔVm = 2.62 cm³/mol) and increases further the glass transition temperature (ΔTg=70 °C). FTIR spectra reveal the formation of P–O–Pb and P–O–Zn bonds in these glasses and show that metaphosphate network is not affected when PbO content increases. Thus, PbO is assumed to play an intermediate role in a way that Pb²⁺ cation tends to break P–O–P bonds forming PbO₄ units with covalent Pb–O bonds. The predominant structural units in all these glasses are metaphosphate (P₂O₆)²⁻ groups. Moreover, systematic variations of the glass transition temperature, density, and molar volume observed are in agreement with these results. of the studied glasses in the water is enhanced as PbO contents increases.