Synthesis of Y ₃Fe ₅O ₁₂ (YIG) assisted by high-energy ball milling

Yttrium iron garnet, Y ₃Fe ₅O ₁₂ (YIG) powders were synthesized by mechanochemical processing (MCP) from Fe ₂O ₃ and Y ₂O ₃, followed by an annealing. The aim of this work was to demonstrate that MCP followed by annealing at relative low temperatures can induce the formation of nanostructured YIG. The effect of synthesis process on the final magnetic properties was also studied. The precursors mixed in a stoichiometric ratio to obtain YIG were milled at room temperature in a shaker mixer mill with a ball:powder weight ratio of 10:1. In order to achieve a single-phase of nanostructured YIG a short thermal annealing at temperatures from 700 to 1100°C was done. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the synthesized powders. The milling process promotes the formation of a perovskite phase (orthoferrite YFeO ₃) independent from the milling time; garnet could only be obtained after an annealing process. The partial formation of the garnet phase was observed in mixtures milled for 5 h. In order to obtain a pure YIG, it is necessary to do a post-treatment of an annealing at temperatures of 900°C, around 400°C lower than those used to prepare the material by solid state reaction. Also, the effect of synthesis method into the magnetic behavior of the garnet was shown.