Grain and grain boundary effects on the frequency and temperature dependent dielectric properties of cobalt ferrite–hafnium composites

CoFe 2 O 4 magnetic ceramic derived from gel and densified by spark plasma sintering

“…This difference can be explain by a relaxation phenomenon which take place at higher frequencies as it will be shown below by dielectric modulus formalism. Anyway, very similar results were reported recently in[15][16][17][18][19][29][30][31][32][33]. The authors explain that electron hopping between Fe 2+ and Fe 3+ and hole hopping between Co 2+ and Co 3+ are responsible for the high conductivity in CoFe 2 O 4 .…”

“…A C C E P T E D ACCEPTED MANUSCRIPT dielectric behaviour of these ferrites [15][16][17][18][19], CoFe 2 O 4 ferrites being potential candidates for booth magnetic and electric applications. The dielectric investigation can provide important information on the behaviour of localized electric charge carriers, giving rise to a better understanding of the mechanism of dielectric polarization.…”

“…Specifically, dielectric behavior is one of the most important properties of ferrites which depend on the preparation conditions, e.g. sintering time, and temperature and heating and cooling rate [15][16][17][18][19].…”

“…Anyway, the results on the real part of permittivity reported here agree very well with the results reported in Refs. [15][16][17][18][19][28][29][30][31][32][33]. They explain that the high values of permittivity (ԑ'~ 4000 at room temperature) in low frequency range are due to Maxwell Wagner type interfacial polarization coming from grain boundaries and surface polarization.…”

“…grains and grain boundaries) or from electrical interfaces (electrodes)[17,18,24,25,[30][31][32][33]. The complex impedance plot fromFig.7shows flattened semicircle with two components: the high-frequency arc is usually associated to the bulk (grain cores), while the low frequency arc to the grain boundaries contributions[17, 18, 24- 25].…”