Effect of Bi3+ on the physical, mechanical, and dielectric properties of cadmium silicate glasses for energy storage devices

Abstract

Glasses with the composition of (60 − X)CdO–XBi₂O₃–40SiO₂ (X = 0, 7.5, 15, and 30 mol%) were synthesized by melt-quenching. Their physical properties and FTIR spectra confirmed that the network strength weakened with the increase in CdO substitution by Bi₂O₃. The incorporation of Bi₂O₃ disrupts Si–O–Si bonds, forming non-bridging oxygen atoms that increase the molar volume and reduce the packing density. Dielectric spectra (0.1 Hz–10 MHz and 30–150 °C) showed increased permittivity and dielectric loss with Bi₂O₃ addition, strong frequency/temperature dependence, and thermally activated mid-frequency relaxations. The AC conductivity increased with the frequency: gradually (0.1–10 Hz), moderately (10 Hz–100 kHz), and sharply (1–10 MHz). The permittivity ranges are 18–27 (X = 0), 17–45 (X = 7.5), 17–55 (X = 15), and 24–65 (X = 30), with maxima at 0.1 Hz and over a temperature range of 30–150 °C. Doped samples exhibited conductivity shoulders coinciding with loss peaks. Mechanical moduli and microhardness decreased with Bi₂O₃ addition, confirming network softening. These glasses combined high dielectric performance and thermal stability, with potential for reprocessing, making them suitable for power-electronics components used in applications such as electric mobility, solar inverters, and wind-turbine converters.