Preparation of Strontium Ferrite Particles by Spray Pyrolysis

Abstract

Crystalline, submicrometer strontium ferrite powders, including SrFeO2.97, SrFe2O4, Sr2FeO4, Sr3Fe2O6.16, and SrFe12O19, were prepared by spray pyrolysis of an aqueous solution of mixed metal nitrates. The Sr:Fe mole ratio in the precursor solution was retained in the final products. Phase‐pure materials were typically obtained only at the highest temperatures investigated (>1100°C) and powders prepared at lower temperatures frequently contained crystalline Fe2O3. The as‐prepared particles were unagglomerated, polycrystalline, and hollow at lower temperatures, but densified in the gas phase at higher temperatures to give solid particles. The strontium ferrite (SrFe12O19) system was studied in detail as a representative example of the Sr‐Fe‐O system. At temperatures of 1200°C, dense, phase‐pure magnetoplumbite‐structure material, SrFe12O19, was obtained, while at lower temperatures, small amounts of Fe2O3 were observed. The particles prepared at 800° and 1100°C were 0.1‐1.0 μm in diameter, and consisted of crystallites <100 nm, and were nearly solid. The difficulty in forming phase‐pure SrFe12O19 was the different thermal decomposition temperatures of Sr(NO3)2 (725°C) and Fe(NO3)39H2O (125°C) as demonstrated by thermogravimetric analysis in the SrFe12O19 system.

Nature of the Green Luminescent Center in Zinc Oxide

“…Samples studied include different commercially available ZnO powders and high purity ZnO powders fabricated using spray pyrolysis [6]. Our data show a strong correlation between the green luminescence, the paramagnetic oxygen-vacancy concentration, and the free-carrier concentration.…”

Advanced synthesis of nanostructured materials for environmental applications

“…The droplets act as a kind of reactor in the size of micrometers where the solvent evaporates, the solutes precipitate and a reaction between the reactants takes place leading to the formation of the final product particles, which are collected on a filter at the end of the reactor. ASP is thus capable for the synthesis of nanostructured mixed oxide systems, with high specific area and high concentration of surface defects, in one step and at lower temperatures [10][11][12]. It also enables the synthesis and deposition on porous substrates in one step and has the advantages of precise control of the materials particle composition and of the quantity deposited, as well as its spatial deposition profile along the porous wall.…”

Morphology of Single-Component Particles Produced by Spray Pyrolysis

“…In the case of alloys, complex metal oxides, and other materials containing two or more metals, the coprecipitation is always complicated by differences between the solubilities of the solutes causing solute segregation and affecting phase development (Senzaki et al, 1995). In addition, for some systems the precursor to one material may melt while the other precursor(s) remain as solids .…”