Finite size effects on the electrical properties of sol–gel synthesized CoFe₂O₄powders: deviation from Maxwell–Wagner theory and evidence of surface polarization effects

Abstract

Fine particles of cobalt ferrite were synthesized by the sol-gel method. Subsequent heat treatment at different temperatures yielded cobalt ferrites having different grain sizes. X-ray diffraction studies were carried out to elucidate the structure of all the samples. Dielectric permittivity and ac conductivity of all the samples were evaluated as a function of frequency, temperature and grain size. The variation of permittivity and ac conductivity with frequency reveals that the dispersion is due to Maxwell-Wagner type interfacial polarization in general, with a noted variation from the expected behaviour for the cold synthesized samples. High permittivity and conductivity for small grains were explained on the basis of the correlated barrier-hopping model.

On the structural, magnetic and electrical properties of sol–gel derived nanosized cobalt ferrite

“…It decreases with increase in frequency and remains a constant at higher frequencies. In our frequency regime of measurements (100 kHz to 8 MHz), it is the interfacial and dipolar polarization which contribute to the overall dielectric properties of the sample [22].…”

Enhanced hydrogen storage properties of LiAlH4 catalyzed by CoFe2O4 nanoparticles

“…The details of the preparation procedure are given in the previous report. 53 All handling of the samples was conducted in a glove box (Mikrouna Co., China) under highpurity argon atmosphere (H 2 O: <10 ppm; O 2 : <10 ppm) in order to minimize oxidation and humidity. About 1.5 g of LiAlH 4 was mixed with various mole fractions of CoFe 2 O 4 nanopowder, and then the mixture was loaded into a stainless steel grinding vial (5 cm in diameter, quenching).…”

Evidence for polaron conduction in nanostructured manganese ferrite

“…This is in tune with the Maxwell-Wagner theory. However there are also reports wherein deviation from the Maxwell-Wagner theory has been stated [15].…”