<p>The present study investigates the structural, optical, electrical, dielectric, and impedance properties of the xNa₂O–(0.3-x)TeO₂–0.40ZnO–0.30P₂O₅ (NTZP) glass system (x = 0.05, 0.10, 0.15, and 0.20) synthesized via the melt-quenching technique. x-ray diffraction (XRD) confirmed the amorphous nature of all compositions. Density decreased from 3.71 g/cm³ (x = 0.05) to 3.02 g/cm³ (x = 0.20), while molar volume increased from 30.01 cm³/mol to 43.07 cm³/mol, indicating network expansion. Optical studies revealed a decrease in the optical bandgap (Eₒₚₜ) from 3.15 to 2.43 eV and an increase in Urbach energy (E_U) from 0.31 eV to 0.39 eV, signifying enhanced structural disorder. Electrical and dielectric analyses confirmed that total conductivity (σ_total) increased with Na₂O content, while DC activation energy (E_dc) decreased from 0.78 eV to 0.63 eV, indicating enhanced charge carrier mobility. AC conductivity followed the universal power law, with activation energy (E_ac) decreasing from 0.30 eV to 0.19 eV, suggesting a hopping-based conduction mechanism. Impedance spectroscopy revealed a decrease in bulk resistance, and at x = 0.20, an additional relaxation process emerged, attributed to space charge effects. Modulus analysis indicated thermally activated relaxation, with relaxation energy (E_τ) decreasing from 0.469 eV (x = 0.05) to 0.219 eV (x = 0.20). Modulus scaling confirmed a nearly temperature-independent relaxation behavior. The results demonstrate that increasing Na₂O content enhances ionic conduction, dielectric stability, and charge transport, making NTZP glass systems promising candidates for solid-state electrolytes and high-performance capacitors in energy storage applications.</p> Graphical abstract