Low temperature dielectric dispersion and electrical conductivity studies on Fe2O3 mixed lithium yttrium silicate glasses

• Published in: Journal of non-crystalline solids Vol. 358; no. 23; pp. 3175 - 3186
• Main Authors: Ramesh Babu, N.Ch, Valente, M.A., Narasimha Rao, N., Graça, M.P.F., Naga Raju, G., Piasecki, M., Kityk, I.V., Veeraiah, N.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier B.V 01-12-2012; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Conductivity of specific materials; Cross-disciplinary physics: materials science; rheology; Dielectric dispersion; Dielectric properties of solids and liquids; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Disordered solids; Electrical conductivity; Electronic transport in condensed matter; Exact sciences and technology; Glasses (including metallic glasses); Lithium yttrium silicate glasses; Materials science; Physics; Specific materials; Lithium yttrium silicate glasses; Dielectric dispersion; Electrical conductivity; Polarization; Frequency dependence; Glass; Space charge; Silicates; Relaxation; Quantum tunnel effect; Scaling laws; Absorption spectra; Permittivity; Activation energy; Optical absorption; Quantum theory; Temperature dependence; Experimental data; Impurity density; Electrical properties; Dielectric properties; Infrared spectra; Small polaron; Quantity ratio; Quantum mechanics; Dielectric losses; Electron paramagnetic resonance
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2012.09.011

Lithium yttrium silicate glasses mixed with different concentrations of Fe2O3 of the composition (40−x) Li2O–10Y2O3–50SiO2: x Fe2O3, with x=0.3, 0.5, 0.8, 1.0, 1.2 and 1.5 (all in mol%) were synthesized. Electrical and dielectric properties including dielectric constant, ε′(ω), loss, tan δ, ac conductivity, σac, impedance spectra as well as electric moduli, M(ω), over a wide continuous frequency range of 40Hz to 106Hz and in the low temperature range 100 to 360K were measured as a function of the concentration of Fe2O3. The dc conductivity is also evaluated in the temperature range 100 … 360K. The temperature and frequency dispersions of dielectric constant as well as dielectric loss have been analyzed using space charge polarization model. The ac and dc conductivities have exhibited increasing trend with increasing Fe2O3 content beyond 0.5mol%, whereas the activation energy for the conductivity demonstrated decreasing tendency in this dopant concentration range. Both quantum mechanical tunneling (QMT) and correlated barrier hopping models (CBH) were used for clarification of ac conductivity origin and the corresponding analysis has indicated that CBH model is more appropriate for this glass system. For the better understanding of relaxation dynamics of the electrical properties we have drawn the scaling plots for ac conductivity and also electric moduli. The plots indicated that the relaxation dynamics is independent on temperature but depends on concentration of Fe2O3. The dc conductivity is analyzed using small polaron hoping model. The increase of conductivity with the concentration of Fe2O3 beyond 0.5mol% is explained in terms of variations in the redox ratio of iron ions in the glass network. The results were further analyzed quantitatively with the support of experimental data from IR, optical absorption and ESR spectral studies. The overall analysis has indicated that Li2O–Y2O3–SiO2 glasses containing more than 0.5mol% of Fe2O3 are more suitable for achieving good electrical conductivity in these glasses.
► Glasses of the composition (40−x) Li2O–10Y2O3–50SiO2: x Fe2O3, were synthesized. ► Electrical and dielectric properties over a wide frequency and temperature range were measured. ► The results were analyzed quantitatively with the support of data from IR, OA and ESR spectral studies. ► Overall analysis indicated that the glasses with >0.5mol% Fe2O3 posses good electrical properties.