Characterization and Densification of Garnet-type Y₃Fe₅O₁₂ Powder Prepared by Amorphous Citrate Process

Abstract

Garnet-type Y₃Fe₅O₁₂ powders were synthesized using an amorphous citrate process. The amorphous citrate precursor gel prepared through a liquid phase was at first thermally analyzed in air up to 1000°C a ta heating rate of 10°C/min by means of TG-DTA in order to study its thermal decomposition process. The gel was calcined at 800, 900 and 1000°C in air since no weight change of the sample was detected above 800°C in the TG curve. The powders thus calcined were molded into pellets and sintered in air under various conditions. The sinterabilities of the powders were studied in comparison with those prepared by a solid state reaction of Y₂O₃, and Fe₂O₃ powders. In the amorphous citrate process, the maximum density of 4.83 g/cm³ (93.3% T. D. ) was obtained for the pellet sintered at 1450°C for 2 h using the powders calcined at 900°C for 2 h. Microstructure of its fracture surface observed with a SEM showed its grain size was small and uniform, although the maximum sintered density was lower than that from the solid state reaction. From the XRD line profile analysis and its results on the XRD peak positions for CuK a, radiation, crystallite sizes and lattice constants characterizing the resultant Y₃Fe₅O₁₂ bodies were estimated to be about 30 to 33 nm and 1.236 to 1.236 nm in the calcining range of 800 to 1000°C, respectively.