The glasses in the Bi₂O₃-K₂O-TiO₂-P₂O₅ system were elaborated by the conventional quenching method. Their structure was studied by Raman spectroscopy, and additional information is determined from density measurements and thermal analysis. The optical absorption of the glasses is investigated and it is found that the optical gap and the Urbach energy decrease and increase, respectively, with increasing Bi₂O₃ content. The crystallization of the glasses was performed under controlled heat treatments to develop glass-ceramics. Their dielectric constants are carried out by impedance spectroscopy. The variations of the permittivity (ϵ_r) and the dielectric loss (tanδ) versus frequency and temperature are determined. It is evidenced that the introduction of Bi₂O₃ in the glasses diminished the dispersion at low frequencies. The presence of bismuth oxide in the materials is also beneficial since it allowed the formation of glass-ceramics with high dielectric constant and low dielectric loss.