Author(s)

Mamilla Lakshmi¹, Katrapally Vijaya Kumar^2*, Krishnan Thyagarajan³

¹Marri Laxman Reddy Institute of Technology & Management, Hyderabad, India.
²Department of Physics, Jawaharlal Nehru Technological University Hyderabad College of Engineering Jagtial, Karimnagar, India.
³Department of Physics, Jawaharlal Nehru Technological University Anantapur College of Engineering, Pulivendula, India.

The series of Cr-Zn nano ferrites having the general composition Cr_xZnFe_2-xO₄ (0 ≤ x ≤ 0.5) have been synthesized successfully in the nanocrystalline form using the sol-gel method. The samples were sintered at 900°C for 3 hours. The effect of chromium substitution on dielectric properties of Zn-ferrites is reported in this paper. The analysis of XRD patterns revealed the formation of single phase cubic spinel structure for all the Cr-Zn ferrite samples. The FTIR spectra show two strong absorption bands in the range of 400 - 600 cm^-1, which corroborate the spinel structure of the samples. The average grain size was found to be in the nanometer range and of the order of 43 - 63 nm obtained using TEM images. The lattice parameter and crystallite size decrease with increase in Cr concentration (x). The investigation on dielectric constant (ε'), dissipation factor (D) and ac conductivity (σ_ac) was carried out at a fixed frequency 1 kHz and in the frequency range of 100 Hz to 1 MHz at room temperature using LCR meter. The plots of dielectric constant (ε') versus frequency show the normal dielectric behavior of spinel ferrites. The value of ac conductivity (σ_ac) increases with increase in frequency for all the compositions. The appearance of the peak for each composition in the dissipation factor versus frequency curve suggests the presence of relaxing dipoles in the Cr-Zn nano ferrite samples. It is also found that the shifting of the relaxation peak towards lower frequency side with an increase in chromium content (x) is due to the strengthening of dipole-dipole interactions. The composition and frequency dependence of the dielectric constant, dielectric loss and ac-conductivity are explained based on the Koop’s two-layer model, Maxwell-Wagner polarization process, and Debye relaxation theory.

Cr-Zn Nano Ferrites, Dielectric Constant, Dissipation Factor, AC Conductivity, Dipole-Dipole Interaction

Lakshmi, M. , Kumar, K. and Thyagarajan, K. (2016) Study of the Dielectric Behaviour of Cr-Doped Zinc Nano Ferrites Synthesized by Sol-Gel Method. Advances in Materials Physics and Chemistry, 6, 141-148. doi: 10.4236/ampc.2016.66015.