Oxygen vacancies and F+ centre tailored room temperature ferromagnetic properties of CeO2 nanoparticles with Pr doping concentrations and annealing in hydrogen environment

Abstract We have investigated ferromagnetic and optical properties, local geometrical structure for Ce1-xPrxO2 (x = 0, 2, 4, 6 and 8% Pr doping) co-precipitation method-synthesized nanomaterials, which were hydrogenated subsequently. Dopant ion concentration, its valence state and effect of hydrogen annealing are correlated with oxygen vacancies and their role in magnetism is discussed with X-Ray diffraction, Raman spectroscopy and Magnetic measurements. The results support the fluorite structure formation for Pr-doped CeO2 nanomaterials without any impurity phase. Red shifting of band gap energy with increased Pr concentration can be seen in the absorption spectra. Raman active modes at ∼500-650 cm−1 confirm the formation of oxygen vacancies, varying with Pr4+/Pr3+ ions in the CeO2 lattice. A sharp peak at ∼3611 cm−1 in FTIR spectra broadens on interaction with H, due to combination of Hydrogen with adjacent Oxygen forming OH moiety within the CeO2 lattice. The magnetization results performed at room temperature confirm ferromagnetic signal for all the samples, with enhanced/reduced FM ordering for different Pr doping fluencies, explained by F-Centre exchange Mechanism with the formation of various complexes, Ce4+-Vo-Ce3+, Pr4+-Vo-Ce3+, or Pr3+ -Vo-Ce3+ in the CeO2 lattice. These nanomaterials are suitable for various applications e.g. Solid state electrolyte for fuel cells, UV blockers, photo-catalyst, magneto-optic devices and primarily for spintronics applications.