Zn-Co ferrites doped with Er³⁺ and Pr³⁺ with different concentrations were synthesised by co-precipitation method at constant calcination temperature. XRD results show an increase in the lattice parameter. Particle sizes determined from TEM are close to those determined from XRD, confirming PVP acts as controlling of the nanoparticles growth. Electron paramagnetic resonance (EPR) spectra analysis indicates that the spin-spin relaxation time T₂ increases and the g-factor decreases with increasing Er³⁺ and Pr³⁺ content. The saturation magnetisation and the coercivity decrease with increasing RE³⁺ content. The dielectric constants ε’ and ε” and the dielectric loss tangent (tanδ) decrease, and the a.c. conductivity increases with the increase of Er³⁺ concentration between 0.00 wt% and 0.20 wt%; the same trend is observed for samples doped with Pr³⁺ of concentrations 0.04, 0.12 and 0.20 wt%, while that doped with 0.08 wt% of Pr³⁺ shows a peak at low frequency.

The increase in environmental pollution, especially water pollution, has intensified the requirement for new strategies for the treatment of water sources. Furthermore, the improved properties of nano-ferrites permit their usage in wastewater treatment. In this regard, novel Mg_0.33Ni_0.33Co_0.33La_xFe_2−xO₄ nanoparticles (NPs), where 0.00≤x≤0.08, were synthesized to test their photocatalytic, antibacterial and antibiofilm activities. The structural and optical properties of the prepared NPs were investigated by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), UV-Vis spectroscopy and photoluminescence (PL) analysis. As La content increases, the bandgap energy increases, whereas the particle size decreases. The photocatalytic activity of the prepared NPs is evaluated by the degradation of methylene blue (MB) dye under sunlight irradiation. Superior activity is exhibited by Mg_0.33Ni_0.33Co_0.33La_0.01Fe_1.99O₄ NPs. The influence of catalyst dosage, pH, temperature and addition of graphene (Gr) on the photodegradation reaction was studied. Increasing the pH and temperature improved the rate of the photodegradation reaction. The antibacterial and antibiofilm activities of the NPs were assessed against Escherichia coli, Leclercia adecarboxylata, Staphylococcus aureus and Enterococcus faecium. Mg_0.33Ni_0.33Co_0.33Fe₂O₄ NPs inhibited bacterial growth. They had bacteriostatic activity on all isolates, with a greater effect on Gram-positive bacteria. All tested nano-ferrites had significant antibiofilm activities against some biofilms.

Ceramic superconducting samples of type (nano-Ag)xCu0.5Tl0.5Ba2Ca2Cu3O10-δ, 0.0 ≤ x ≤ 3.0 wt.%, were successfully synthesized via single step solid-state reaction technique at 850 ºC and under ambient pressure. The samples were characterized by XRD and SEM. Obtained data revealed that the highest grains connectivity volume fraction was detected for the sample with x = 0.15 wt.%. The electrical properties of the prepared samples was examined using the electrical resistivity measurements, and the results proved that the highest superconducting transition temperature Tc was observed at x = 0.15 wt.%. Furthermore, the fluctuation conductivity Δσ(T), above Tc, was analyzed as a function of reduced temperature, t=(T-T_c^mf)/(T_c^mf ), using Aslamazov and Larkin (AL) theory and its modified form given by Lawrence-Doniach (LD) model. Excess conductivity analysis showed crossover between two dimensional (2D) to three-dimensional (3D) with decreasing temperature for all samples. The highest crossover temperature T2D-3D was observed for x = 1.5 wt.%, which showed the smallest coherence length along c-axis ξ(0), Fermi velocity vF, Fermi energy EF and interlayer coupling ν in these samples.