Microstructure, frequency and temperature-dependent dielectric properties of cobalt-substituted lithium ferrites

• Published in: Journal of magnetism and magnetic materials Vol. 214; no. 1; pp. 55 - 60
• Main Authors: Watawe, S.C, Sarwade, B.D, Bellad, S.S, Sutar, B.D, Chougule, B.K
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 2000; Elsevier Science
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Conductivity phenomena in semiconductors and insulators; Dielectric properties; Dielectric properties of solids and liquids; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Electrical properties; Electronic transport in condensed matter; Exact sciences and technology; Ferrites; Microstructure; Mobility edges ; hopping transport; Physics; Ferrites; Electrical properties; Microstructure; Dielectric properties; Temperature dependence; Frequency dependence; Lithium oxides; Inorganic compounds; Electrical conductivity; Phenomenological theory; Transition element compounds; Cobalt oxides; Experimental study; Hopping conduction; Dielectric losses; Iron oxides; Quaternary compounds; Permittivity
• ISSN: 0304-8853
• DOI: 10.1016/S0304-8853(00)00033-0

Ferrites with the general formula Li
0.5−
x/2
Co
x
Fe
2.5−
x/2
O
4 (where
x=0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7) were prepared by the standard ceramic method. AC resistivity (
ρ
AC
), dielectric constant (
ε′) and dielectric loss tangent
(tan
δ)
were measured as a function of frequency and temperature. The compositional variations of
ρ
DC and
ε′ with
x show inverse trends with each other. The dielectric constant increases slowly from 0 to 450 with temperature in the beginning and sharply after 200°C. The
ε′ and
ρ
DC show a decrease with increase in frequency for all the samples. The variation of
tan
δ
with frequency shows cusps for all the samples except for
x=0.5. These variations have been explained on the basis of Koop's phenomenological theory, concentration of Fe
2+ and Fe
3+ ions on octahedral site and hopping frequency of electrons between Fe
2+ and Fe
3+.