Comparative study of structural, optical and magnetic properties of Fe–Pt, Fe–Cu and Fe–Pd-codoped WO₃ nanocrystalline ceramics: effect of annealing in hydrogen atmosphere

Tungsten oxide (W-oxide) nanoparticles doped and codoped with different transition-metal (TM) ions (Fe, Pt, Cu and Pd) were synthesized by hydrochloric acid-assisted precipitation. The synthesized powders were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS) and magnetic characterization methods. The room temperature (RT) monoclinic (P21/n) structure founded for pristine WO₃ nanopowder was converted into orthorhombic (Pbam) structure by Fe-doping, while codoping, (Fe–Pt) and (Fe–Cu) preserved the P21/n space group (SG) structure. It was found that the hydrogenation of the synthesized doped-samples corroded the crystallites without changing the crystalline SG structure. Moreover, controllable room temperature ferromagnetic (RT-FM) properties were created by hydrogenation of the codoped W-oxide samples. The oxygen vacancies-mediated ferromagnetic (FM) interaction could be responsible for the observed FM. The relative highest RT-FM energy was created with hydrogenated Fe–Pd codoped W-oxide. Therefore, Fe–Pd-codoped W-oxide nanopowder could be considered as a potential candidate for many applications involving partial FM properties, such as catalysts and optical phosphors. (author)