Synthesis of gallium bearing magnetic particles from aqueous solution: influence of mixing procedure of initial solution and the ratio of Ga/Fe

Gallium-bearing magnetite particles were synthesized by aerial oxidation of alkaline suspension containing both ferrous and gallium ions. It was found that the mixing procedure and temperature were critical in the preparation of ferrite particles without the formation of α-FeOOH (ferric oxyhydroxide), non-spherical particles and amorphous phase, evidenced by characterization of SEM and XRD. On the other hand, the concentration of Ga3+ entry into the structure of spinel was different with the mixing procedure and temperature. Single phase of spinel gallium-bearing magnetites were precipitated at the temperature from 25 to 90 °C in the C procedure in which the neutralization of Ga was performed firstly, but the concentration of Ga entry into spinel of magnetites decreased with the temperature increasing. While in the procedure D in which neutralization of Fe ions was performed firstly, single phase of spinel gallium-bearing magnetites were precipitated only at the temperature above 65 °C, and the content of gallium precipitated into the magnetites increased with the temperature. Mossbauer analysis and magnetic characteristic were used to investigate the cation distribution of the gallium bearing ferrites with different ratio of Ga3+/Fe2+, which showed small content gallium introduction to have entered the tetrahedral sites preferentially rather than the octahedral sites, and increasing gallium introduction to have located between octahedral and tetrahedral sites.