Synthesis and physical characterization of amorphous silicates in the system SiO2-Na2O– RO (R = Zn, Pb or Cd)

Abstract

Glasses of the composition (mol%) 65 SiO2, 20 RO, 15 Na2O, where R is Zn, Pb or Cd, were prepared by the melting quenching technique. It is aimed to investigate the structural, optical and, for the first time, their electrical and dielectric properties of these glasses. FTIR revealed that modifier oxide tetrahedral structural units and chemical resistivity increase, while non-bridging oxygens (NBOs) decrease as ZnO is replaced by CdO or PbO. The absorption edge shows a red shift in the same direction of replacement, which was ascribed to the decrease of the strength of oxygen bonding and increase of polarizable NBOs. Refractive index, density, molar volume and optical band gap energy (Eopt) were determined. The dielectric constant attained higher values for glass containing ZnO than those containing CdO or PbO. The ac conductivity behavior is interpreted in terms of overlapping-large polaron tunneling model and the correlated barrier hopping model. The electronic-type conductivity dominates in the studied glasses containing CdO or PbO. The ac conductivity values of the studied glasses increase with increasing frequency, indicating their semiconducting nature. The obtained values of electrical conductivity and capacitance may allow considering the investigated glasses for use in electronic devices.