Aerosol synthesis of gadolinium iron garnet particles

Particles of gadolinium iron garnet, Gd₃Fe₅O₁₂, were produced primarily by an aerosol spray pyrolysis technique starting with solutions of gadolinium and iron nitrates. The as-prepared particles were polydisperse solid spheres. Average diameters in the range 0.05 to 0.8 μ could be obtained by variation of the initial solution concentration. Larger particles to 2 μ were created by direct, non-aerosol, pyrolysis of the solutions. Heat treatment caused sintering and particle coalescence and yielded ∼95% garnet phase. The reaction time to create the garnet phase scaled with the square of the particle diameter, the smallest particles transforming the quickest. Magnetic measurements showed bulk behavior for the saturation magnetization, but the coercivity could be varied with particle size with a maximum near the single domain size.