Abstract
xLa
2O
3–30PbO–(70
−
x)B
2O
3 (0
≤
x
≤
10
mol%) glasses have been investigated by Fourier transform infrared spectroscopy, and ultrasonics. Deconvolution of infrared spectra reveals a small increase with
x in the fraction of four-coordinated boron atoms. These results show that La
3+ ions have priority to form BO
4 units at the expense of Pb
2+ ions. A minimum in the sound velocity, elastic properties and transition temperature of glasses observed at 5
mol% La
2O
3 is correlated with the change in the packing of glass. Higher rate of increase in density for
x
≥
5
mol% is considered due to an increase in the concentration of PbO
4 units.