Er–Mg–Cu Ferrite Nanoparticles: a Synergetic Effect of Rare Earth RE-Er3+ on Enhanced Surface Morphological, Optical, and High-Temperature Electrical Properties

Mg_0.5Cu_0.8Er_xFe_2−xO₄ (through x = 0.000, 0.005, 0.010, 0.015, 0.020, 0.025 and 0.030) A series of rare earth (Er³⁺)-doped magnesium-copper nanoparticles with the general chemical compositions of Mg0.5Cu0.8ErxFe2−xO4 (through x = 0.000, 0.005, 0.010, 0.015, 0.020, 0.025 and 0.030) was fabricated by citrate sol–gel auto combustion technique. The fabricated materials are investigated through XRD, FE-SEM, EDS, TEM, FTIR, UV–Vis, DC resistivity, and TEP properties. The crystallite size of the samples was determined to be 33–40 nm with increased Er³⁺ concentration, and the XRD investigations validated the spinel cubic structure of the samples with the space group Fd-3 m. The lattice constant was found to decrease from 8.403 to 8.356 Å. The morphology of FE-SEM micrographs was found to be spherical shape. TEM micrographs show that average particle size decreases from 64 to 48 nm. The nanoparticles’ FTIR examination revealed that their ʋ₁ and ʋ₂ absorption bands were between 401–412 cm⁻¹ and 547–562 cm⁻¹. The optical band gap was measured using UV–vis spectroscopy and found between 1.81 and 2.38 eV. In Mg–Cu nano-ferrites with Er-doping, there was no noticeable increase in the elasticity moduli. With increasing Er-doping and composition, it has been found that the thermal energy needed to change the p-type Mg–Cu nano-ferrites’ behavior from semiconducting to n-type semiconducting behavior increases. Er-doped Mg–Cu ferrites demonstrate a metal–semiconductor behavior according to DC resistivity exploration.