Structural, magnetic, optical and ferroelectric properties of Y3+ substituted cobalt ferrite nanomaterials prepared by a cost-effective sol-gel route

In recent years, the popularity of spinel ferrite nanomaterials has increased due to their widespread applications in the electronics industry, energy storage and environmental monitoring. In the present research, the Yttrium-substituted CoYxFe2-xO4 nanomaterials (x = 0.0, 0.1, 0.2 and 0.3) were synthesized between 400 and 750 °C by a sol-gel process. The XRD confirmed the cubic phase of CoYxFe2-xO4, where the crystallite size, lattice constant and micro strain had a noticeable decrease with increasing Y3+ content (x). The Rietveld refinements exhibited a better goodness of fit between 1.02 and 1.32. The surface morphology of CoFe2O4 and CoY0.3Fe1.7O4 samples revealed agglomerated and porous structures with an average grain size of 1.24 and 2.50 μm, respectively. The porosity is highly increased with increasing Y3+ content as evident from XRD and SEM. HRTEM confirmed particle size of CoYxFe2-xO4 (x = 0.0 and 0.3) near 30.40 and 10.92 nm, respectively. The FTIR spectroscopy identified slight shift towards higher wavenumbers with increasing Y3+ content owing to the perturbation occurring between metal-oxygen bonds. The highly increased direct band gap from 3.39 to 3.91 eV may be noble findings for CoYxFe2-xO4 materials. The room temperature PL emissions between 457 and 520 nm reveal the radiative defects and oxygen vacancies in the prepared ferrites. The systematic decrease in coercivity, saturation magnetization, retentivity and anisotropy constant from 1173 to 666 Oe, 69.95 to 42.38 emu/g, 33.24 to 13.45 emu/g and 0.773 × 106 to 0.301 × 106 erg/cm3, respectively at room temperature for CoYxFe2-xO4 nanomaterials may be responsible for its possible use in magnetic hyperthermia. The ferroelectric P-E loop between 3 and 5 KV has shown the largest loop area of CoFe2O4, which decreased with Y3+ substitution. The high P-E loop area represents higher leakage currents, which is also evident from J-E plots. Thus, the structural, optical, magnetic and ferroelectric properties of CoYxFe2-xO4 nanomaterials could make it useful in opto-electronic, photocatalytic, magnetic and environmental applications.