Srđan Rakić

Low Temperature Synthesis of Nanocrystalline ZnFe2O4 Powders

Advances in nanoscale electronics require superior ceramic powders, preferable prepared with techniques for the direct synthesis of crystalline nanoparticles. Zinc ferrite (ZnFe2O4) nanopowders were prepared by co-precipitation method, from nitrate precursors. Crystalline powders having the single-phase cubic spinel structure were directly synthesized at temperature ≥80°C in the presence of NaOH. The obtained powders are agglomerated with ultra-fine crystallites having the average crystallite size about 3-4 nm.

Conductivity and dielectric behaviour of indium substituted zinc ferrites prepared by coprecipitation method

This paper presents the results concerning dielectric behavior and conductivity of the nanosized Zn1−xInxFe2O4 powders (x = 0, 0.15, 0.2, and 0.3), obtained by coprecipitation method. The frequency dependence of dielectric permittivity and conductivity of the samples is determined in the frequency range of 1–105 Hz, at temperatures from 300–350 K, while the temperature dependence of conductivity was recorded at 100 Hz, 10 kHz and 100 kHz. The ac conductivity was found to follow universal dielectric response, which is typical for charge transport by hopping or tunneling processes. Analyzing the variation of the parameter n (as a measure of the degree of correlation between conductivity and frequency), with the temperatures we discuss the possible conduction mechanism in investigated samples. Qualitatively, non-overlapping small polarons (NSPT) are usually associated with increase in n with increasing temperature, while correlated barrier hopping (CBH) shows a decrease in n with increasing T.