The study of barium ferrites(M=BaFe12O19) synthesis during tartrates process

• Main Authors: Chen-Tzung Hong, 洪辰宗
• Other Authors: Fu-Su Yen
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/89789905451538729224

碩士 === 國立成功大學 === 資源工程學系碩博士班 === 91 === This study utilized the metal-tartrate method to synthesize submicrometered (＜1μm) barium ferrite (M=BaFe12O19) powders. Two experimental factors that influence the ferrite formation: (1) the molar ratio of tartaric acid/ cation and (2) the pH value of solutions were examined. It is found that: 1. BaFe12O19 formation: The Ba-Fe-tartrates obtained at molar ratio of tartaric acid/ cation (T/C) ~1 would transfer to a mixture of Ba-compound (unidentified amorphous or microcrystalline phases) + g-Fe2O3 at 250oC. The mixture then reacted to form BaFe12O19 at temperature ＞700℃. The BaFe2O4 phase as generally observed during synthesis of the ferrite using solid-state reaction did not occur. Formation of BaFe12O19 may relevant to g- to a- phase transformation of Fe2O3. The ferrite phase can be formed at temperature as low as 400℃ (selecting pH=7 and T/C=1.3 systems). The formation mechanism for BaFe12O19 formation is: Metal-tartrates g-Fe2O3 + Ba-compound BaFe12O19. 2. BaFe2O4 formation: The decomposition of barium carbonate (BaCO3, witherite) that occurred at two temperature intervals 450~550oC and ~600oC, respectively can be the controlling factor for BaFe2O4 formation. The Ba2+ cation then reacted with Fe2O3 to form BaFe2O4 that behaved stably, persisting to higher temperatures. 3.The synthesis of mono-phased BaFe12O19 powders then can be obtained using the organo-metallic system of T/C molar ratio ~ 1. Transferring the precipitate to a mixture of Ba-compounds and g-Fe2O3 at 250oC then a direct formation of BaFe12O19 powders can be obtained by calcinations of the mixture at ~700oC.