Effect of Polyethylene Glycol (PEG-4000) on Dielectric Properties of Mn0.5Zn0.5Fe2O4 Nanoparticles

Abstract

Dielectric properties of Mn0.5Zn0.5Fe2O4 nanoparticles (NPs) encapsulated by polyethylene glycol (PEG) has been studied as a function of frequency in the range 5 kHz to 120 kHz at room temperature. PEG-encapsulated Mn0.5Zn0.5Fe2O4 NPs were synthesized by co-precipitation method with various PEG concentration. X-ray diffraction (XRD) pattern confirmed that Mn0.5Zn0.5Fe2O4 NPs have cubic spinel structure. The crystallite size of the sample was 12.5 nm and then decreased with the increase of PEG concentration. It is due to the agglomeration reduced after PEG encapsulation. The real dielectric constant (ϵ′) of the sample was 320.2 and decreased with the increase of PEG concentration, it is expected because of a decrease of crystallite size. The imaginary dielectric constant (ϵ′) and loss tangent (tan δ) of the samples have a value 360.2 and 1.1 respectively and decreased with the increase of PEG concentration, which is due to the decrease in drift mobility of electric charge carries. The AC conductivity (σ) of the sample was (1.1 × 10-4) kΩ-1 and decreased with the increase of PEG concentration, this may be due to the change in cation distribution of the sample. The capacitance of the sample was (4.5 × 10-11) Farad and decreased with the increase of PEG concentration, it is also caused by the decrease of crystallite size. Furthermore, the real dielectric constant (ϵ′) and imaginary dielectric constant (ϵ′) of the samples have a value 521.1 and 393.8 respectively and decreased with increasing applied frequency; it is due to the fact that above certain frequencies the electronic exchange between the ferrous and ferric ions does not follow the applied field. The AC conductivity of the sample was (2.1 × 10-4) kΩ-1 and increased with increasing applied frequency, contrary the capacitance (C) of the sample was (1.3 × 10-10) Farad and decreased with increasing applied frequency. This can be attributed to the conductive grains become more active at the higher frequency, hence increasing the hopping frequency of electron Fe3+ and Fe2+ ions. The refractive index (n) of the sample was 24.2 and increases with the increase of dielectric constant at low frequency.