| Summary: | 碩士 === 淡江大學 === 化學工程與材料工程學系碩士班 === 97 === Hexagonal barium ferrite (BaFe12O19) powders with superior magnetic properties were synthesized using a modified co-precipitation method. One hundred milliliters of the aqueous solution, containing the stoichiometric amounts of barium and iron nitrates to form BaFe12O19, were added into the 400-mL solution of acetone and ammonia, which was controlled at 30 C, to undergo precipitation reaction for 3 h. The relative amounts of acetone and ammonia in the solution were varied according to R (define : volume of ammonia used/the total volume of the solution of acetone and ammonia) and R ranged from 0 to 1. After being centrifugally separated, the collected particles were dried at 300 C, followed by calcining at temperatures (T) between 600 ~ 900 C. The calcined particles were then characterized using x-ray diffractometer, infrared spectrometer, scanning electron microscope, transmittance electron microscope, and vibrating sample magnetometer. The experimental results indicated that crystalline BaFe12O19 was able to be formed at 650 C but the specimen still contained some BaCO3 and a-Fe2O3. To obtain pure BaFe12O19 powder, calcining the precipitates at 800 oC were required. When R = 0.6 and T = 800 oC, the obtained BaFe12O19 powder exhibited saturated magnetization of 67.7 emu/g and coercive force of 4.84 kOe.
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