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В. С. Бушкова
«Комплексні імпедансні діелектричні властивості нікель-кобальтових феритів»
387–402 (2016)

PACS numbers: 72.20.-i, 72.80.Sk, 75.50.Gg, 75.50.Tt, 77.22.-d, 77.84.Bw, 85.70.Ge

In a work, the frequency–temperature dependence of the dielectric properties of nickel–cobalt ferrites fabricated by sol–gel processing with autocombustion synthesis is studied by means of the impedance-spectroscopy method. The results of study of the dielectric properties of Ni1?xCоxFe2O4 ferrites in the temperature range 298–723 K are given for the frequency range 10–2–106 Hz. As detected, the course of curves represented in Nyquist coordinates depends on temperature. As found, with increasing frequency, the real (??) and imaginary (??) components of the dielectric permeability decrease due to the polarization-process mechanism that is characteristic for the ferrites. The dependence ??(f) indicates the presence of direct current conductivity in the sample that influences on the significantly increasing dielectric response with increasing temperature. As shown, with increasing temperature, conductivity of nickel–cobalt ferrites increases too. As detected, the activation energy of conductivity, ?dc, at high temperatures (Т???445 K) increases significantly for all samples, which contain the Ni2+ ions. This is due to a change in mechanism of conductivity in the temperature range 425–445 K.