Elastic study and optical dispersion characterization of Fe-substituted cobalt aluminate nanoparticles

Abstract

The point of this work is to study the impact of Fe³⁺ ions substitution on the structural, elastic and optical properties of CoAl₂O₄ nanoparticles. A series of CoAl_2−xFe_xO₄ nanoparticles, 0.00 ≤ x ≤ 0.20, are prepared by chemical co-precipitation method. X-ray diffraction besides the FTIR examination affirms the forming of single-phase cubic spinel CoAl₂O₄ for Fe³⁺-substituted samples. The lattice constant a is found to be increased with increasing Fe³⁺ content obeying Vegard’s law. The dependence of theoretical density, porosity and crystallite size on Fe³⁺ content x is discussed. FTIR spectral analysis is used to estimate the elastic moduli such as stiffness constant, Young’s modulus, rigidity modulus, bulk modulus, Poisson’s ratio, wave velocity and Debye temperature. The stiffness constants and Poisson’s ratio increase with the increase in Fe³⁺ content due to the decrease in porosity and substitution process. The values of Young’s modulus, rigidity modulus and Debye temperature reduce with an increase in the Fe³⁺ content, whereas the bulk modulus increases with x. The optical properties of CoAl_2–xFe_xO₄ nanoparticles are analyzed using UV–Vis spectrophotometer measurements in the spectral range of 200–1100 nm. Some of dispersion parameters are evaluated based on a single oscillator model, such as oscillator energy E_o, dispersion energy E_d, lattice dielectric constant ε_l, the average value of oscillator strength, S_O, and wavelength of single oscillator λ_O. The most important result of the current work is the use of Fe³⁺ ion substitution in CoAl₂O₄ nanoparticles, which can be used to modify the elastic moduli, optical band gaps and dielectric constant.