Compositional dependence of the structural and dielectric properties of Li2O–GeO2–ZnO–Bi2O3–Fe2O3 glasses

• Published in: Journal of materials science 2011-03, Vol.46 (5), p.1295-1304
• Main Authors: Salem, Shaaban M., Antar, E. M., Mostafa, A. G., Salem, S. M., El-badry, S. A.
• Format: Article
• Language: English
• Subjects: Bismuth oxides; Bismuth trioxide; Characterization and Evaluation of Materials; Chemistry and Materials Science; Classical Mechanics; Conductivity; Crystallization; Crystallography and Scattering Methods; Density; Dielectric loss; Dielectric properties; Differential thermal analysis; Direct current; Germanium oxides; Glass; Glass transition temperature; High temperature; Infrared analysis; Infrared spectroscopy; Ion concentration; Iron; Iron oxides; Lithium oxides; Materials Science; Molar volume; Networks; Permittivity; Polymer Sciences; Solid Mechanics; Spectra; Temperature; Temperature dependence; Zinc oxide
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-010-4915-4

(10Li 2 O–20GeO 2 –30ZnO–(40- x )Bi 2 O 3 – x Fe 2 O 3 where x  = 0.0, 3, 6, and 9 mol%) glasses were prepared. A number of studies, viz. density, differential thermal analysis, FT-IR spectra, DC and AC conductivities, and dielectric properties (constant ε′, loss tan δ, AC conductivity, σ ac , over a wide range of frequency and temperature) of these glasses were carried out as a function of iron ion concentration. The analysis of the results indicate that, the density and molar volume decrease with an increasing of iron content indicates structural changes of the glass matrix. The glass transition temperature T g and onset of crystallization temperature T x increase with the variation of concentration of Fe 2 O 3 referred to the growth in the network connectivity in this concentration range, while glass-forming ability parameter Δ T decrease with increase Fe 2 O 3 content, indicates an increasing concentration of iron ions that take part in the network-modifying positions. The FT-IR spectra evidenced that the main structural units are BiO 3 , BiO 6 , ZnO 4 , GeO 4 , and GeO 6 . The structural changes observed by varying the Fe 2 O 3 content in these glasses and evidenced by FTIR investigation suggest that the iron ions play a network modifier role in these glasses while Bi 2 O 3 , GeO 2 , and ZnO play the role of network formers. The temperature dependence of DC and AC conductivities at different frequencies was analyzed using Mott’s small polaron hopping model and, the high temperature activation energies have been estimated and discussed. The dielectric constant and dielectric loss increased with increase in temperature and Fe 2 O 3 content.