Electronic relaxation in zinc iron phosphate glasses

• Published in: Journal of non-crystalline solids Vol. 353; no. 27; pp. 2659 - 2666
• Main Authors: Moguš-Milanković, A., Ličina, V., Reis, S.T., Day, D.E.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.08.2007; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Dielectric loss and relaxation; Dielectric properties of solids and liquids; Dielectric properties, relaxation, electric modulus; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Exact sciences and technology; Permittivity (dielectric function); Phosphates; Physics; Phosphates; Dielectric properties, relaxation, electric modulus; Frequency dependence; Electrical conductivity; Dielectric properties; relaxation; Glass structure; Phosphate glass; Hopping conduction; Dielectric losses; Scaling laws; Chemical bonds; electric modulus; Phosphates; Complex permittivity; Activation energy; Master equations; Polarons
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2007.05.001

The electrical and dielectric properties of 10ZnO–30Fe2O3–60P2O5 (mol%) glasses, melted at different temperatures were measured by impedance spectroscopy in the frequency range from 0.01Hz to 3MHz and over the temperature range from 303 to 473K. It was shown that the dc conductivity strongly depends on the Fe(II)/[Fe(II)+Fe(III)] ratio. With increasing Fe(II) ion content from 17% to 37% in these glasses, the dc conductivity increases. Procedure of scaling conductivity data measured at various temperatures into a single master curve is given. The conductivity of the present glasses is made of conduction and conduction-related polarization of the polaron hopping between Fe(II) and Fe(III), both governed by the same relaxation time, τ. The high frequency dispersion in electrical conductivity arises from the distribution in τ caused by the disordered glass structure. The evolution of the complex permittivity as a function of frequency and temperature was investigated. At low frequency the dispersion was investigated in terms of dielectric loss. The thermal activated relaxation mechanism dominates the observed relaxation behavior. The relationship between relaxation parameters and electrical conductivity indicates the electronic conductivity controlled by polaron hopping between iron ions.