Abstract
Characterizations of the prepared pseudo penta-glass system 60 PbO – (40-x) SiO
2
– x (0.1 Li
2
O – 0.86 B
2
O
3
– 0.04 Dy
2
O
3
) with 0 ≤ x ≤ 30 mol% were performed in terms of the ultrasonic and spectroscopic techniques. The increase of (0.1 Li
2
O – 0.86 B
2
O
3
– 0.04 Dy
2
O
3
) content causes borate structural variations such as the transformation of [BO
3
] to [BO
4
] structural units and enhancement of the compactness of the glasses. These physical parameters play an important role in modifying the mechanical and the optical properties of the lead silicate glasses. The improvement of the mechanical properties is indicated from the increment of the density, the ultrasonic velocities, the elastic moduli (experimentally determined and theoretically computed) and the glass transition temperature. The borate structural variations along with the presence of Dy
2
O
3
decrease both the UV transmission and the optical energy gap, increase the refractive index and created several transitions at different wavelengths.