Aerosol synthesis of gadolinium iron garnet particles
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G. C. Hadjipanayis Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (Received 29 April 1991; accepted 22 October 1991)
Particles of gadolinium iron garnet, Gd 3 Fe 5 0i 2 , 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 n could be obtained by variation of the initial solution concentration. Larger particles to 2 /x were created by direct, non-aerosol, pyrolysis of the solutions. Heat treatment caused sintering and particle coalescence and yielded ~ 9 5 % 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.
I. INTRODUCTION Aerosol synthesis and processing of materials has proven to be a viable and attractive technique. Advantages relative to other synthetic methods include its simplicity, flexibility, and ability to create small particles of high purity. The aerosol spray pyrolysis technique is perhaps the most straightforward of the aerosol methods. W1 In this process dissolution of precursor compounds in water is followed by nebulization, drying, and pyrolysis to create small particles. Earlier work of this type has been successful in creating a variety of metal oxide particles. In this work we have used aerosol spray pyrolysis to create submicron particles of Gadolinium Iron Garnet (GdIG), Gd3Fe5Oi2. The rare-earth garnets are a general class of compounds that display novel and useful magnetic properties and hence are of technological importance.12"14 In particular, GdIG has potential as a magnetic recording medium due to its magnetooptical Kerr effect properties. Hence it is desirable to create this compound in particulate form for coating carrier substrates. It is also desirable to explore in what manner the magnetic properties of this material might be altered by making the material in particle form. In this paper we describe our synthesis method and characterize these particles with x-ray diffraction and SEM. We also studied the magnetic properties of our particles with a SQUID (Superconducting Quantum Interference Device) and vibrating sample magnetometer. Magnetooptical properties of the particles will be described in a separate paper. II. EXPERIMENTAL METHOD Particles were made in two different ways: aerosol spray pyrolysis and direct drying, pyrolysis, and grinding 712 http://journals.cambridge.org
J. Mater. Res., Vol. 7, No. 3, Mar 1992 Downloaded: 12 Mar 2015
of the precursor solutions. Aqueous solutions were made up using appropriate weights of Gd(NO 3 ) 3 • 6H2O and Fe(NO 3 ) 3 • 9H 2 O in distilled, de-ionized water with the atomic ratio of Gd: Fe at 3 : 5 . The aerosol procedure was described earlier. 1011 The tot
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