Effect of Holmium (III) Ion-Doped Nickel-Copper Ferrite Nanoparticle on Structural, Optical, and Dielectric Properties

This article examined the effect of Ho3+-doped Nickel-Copper (Ni-Cu) ferrite nanoparticles on structural, optical, and dielectric parameters. XRD analysis revealed the structural retention in a single-phase cubic spinel structure. It demonstrated increasing Ho3+ ion concentration, with a decreased crystallite size ranging from 37.05 nm to 27.36 nm, mostly ascribed to ionic radii mismatch between the dopant and the pristine. Elemental composition of the sample was analyzed via Energy Dispersive X-ray spectroscopy, which confirms the sample's stoichiometric composition and good chemical purity. UV-Vis spectroscopy measurement revealed that the incorporation of Ho3+significantly reduced the band gap (Eg) from 2.486 electron volts to 2.128 electron volts. This decrease is ascribed to the development of Ho3+-induced defect or impurity energy levels within the Ni-Cu ferrite's forbidden band gap, which enhances visible light absorption. Finally, impedance analysis confirmed the material's characteristic electrical response, revealing a sharp decrease in the real dielectric constant in the lower-frequency regions with applied field frequency, a relaxation phenomenon governed primarily by the Maxwell-Wagner interfacial polarization mechanism.