Microwave combustion synthesis of Co1−xZnxFe2O4 (0 ⩽ x ⩽ 0.5): Structural, magnetic, optical and vibrational spectroscopic studies

• The zinc doped cobalt ferrites were prepared by microwave combustion method.
• DRS and PL studies were performed to study the optical behavior of cobalt ferrites.
• FT-IR spectroscopy confirmed the formation of cobalt ferrite spinel structure.
• Rietveld analysis were carried out to study the structural aspect of the material.

Nanostructured pure and zinc doped cobalt ferrites (Co1−xZnxFe2O4 where x fraction ranging from 0 to 0.5) were prepared by microwave combustion method employing urea as a fuel. The nanostructured samples were characterized by using various instrumental techniques such as X-ray powder diffractometry, high resolution scanning electron microscopy, energy dispersive X-ray analysis, UV–visible diffuse reflectance spectroscopy, photoluminescence spectroscopy and Fourier transformed infrared (FT-IR) spectroscopy. Vibrating sample magnetometry at room temperature was recorded to study the magnetic behavior of the samples. X-ray analysis and the FT-IR spectroscopy revealed the formation of cobalt ferrite cubic spinel-type structure. The average crystallite sizes for the samples were in the range of 3.07–11.30 nm. The direct band gap (Eg) was estimated using Kubelka–Munk method and is obtained from the UV–vis spectra. The band gap value decreased with an increase in zinc fraction (2.56–2.17 eV). The violet and green emission observed in the photoluminescence spectra revealed that cobalt ferrites are governed by defect controlled processes. The elemental analysis of zinc doped cobalt ferrites were obtained from energy dispersive X-ray (EDX) analysis. From the magnetic measurements, it is observed that cobalt ferrite and zinc doped cobalt ferrite systems fall under the soft ferrite category. The saturation magnetization (Ms) value of undoped cobalt ferrite is 14.26 emu/g, and it has reached a maximum of 29.61 emu/g for Co0.7Zn0.3Fe2O4.

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