共沈物의 熟成이 Ba-Ferrite의 合成過程에 미치는 影響

The effect of aging coprecipitate obtained by the reaction of mixed solution1.1 ㏖. FeCl-0.1 ㏖ BaCl₂ and 4.0 ㏖. NaOH-1.0 ㏖. K₂CO₃ on the synthesis process of Baferrite (BaFe 12 O 19 ) was investigated by means of DTA, TGA, XRD and electron microscope. The no-aged coprecipitate seems to be the aggregate of amorphous Fe₂O₃·nH₂O and (1-X) BaCO₃·xBa (OH)₂, but the 30 days-aged to be composed of crystalline Fe₂O₃H₂O and BaCO₃. The decomposition temperature of BaCO₃ in the coprecipitate increases from 400-700℃ to 700-900℃ with increment of aging-time. In the no-aged coprecipitate Ba-ferrite is synthesized through the surface reaction of amorphous Fe₂O₃ and BaO at 600-700℃, but in the 30 days-aged through the ion-diffusion reaction of crystalline α-Fe₂O₃ and skeleton crystal BaO at 800-900℃ with more compact crystalization. During calcination of the 30 days-aged coprecipitate, the intermediate phase BaFe₂O₄ is formed at 600-700℃ and completely transformed to Ba-ferrite at 800-900℃.