New reagents for the chemical synthesis of fine rare-earth orthoferrite powders

Ultrafine (less than or equal to 150 nm) rare-earth orthoferrites (RFeO(3) where R = Sm, Nd, and Gd) with good purity and chemical homogeneity were prepared through two solution-based chemical routes using some new and versatile chemical reagents. The first route involved coprecipitation of mixed metal nitrates from their aqueous solutions, in the presence of water soluble polyvinyl alcohol (PVA), using triethylammonium carbonate solution. The other process involved complete evaporation of a mixture of optimum amounts of PVA and the desired aqueous metal nitrate solutions, with the addition of the optimum amount of urea when the mixture was evaporated to a pasty mass. In addition, detailed study of the reported potassium ferricyanide route was also carried out for the production of the same powders. The precursor as well as the heat-treated RFeO(3) powders, prepared through these three routes, were compared by physical characterization studies involving thermal gravimetry and differential scanning calorimetry (TG/ DSC), Infrared spectroscopy (IR), X-ray powder diffraction (XRD), energy dispersive X-ray spectroscopy (EDXS), transmission electron microscopy (TEM), and room temperature magnetic measurements.