柠檬酸溶胶-凝胶法制备钡铁氧体晶相变化的研究

Crystal change of barium hexaferrite prepared by citric acid sol-gel method

采用柠檬酸溶胶-凝胶法制得钡铁氧体磁性粉末,借助热质量分析(TGA)、红外光谱(FT-IR)、X线衍射(XRD)及扫描电镜(SEM)测试手段研究了不同柠檬酸添加量对煅烧产物晶型的影响。结果表明:当柠檬酸与金属硝酸盐摩尔配比n(CA)/n(MN)≤1.2时,钡铁氧体晶相为W型,当n(CA)/n(MN)=2时,晶相转变为M型;随着柠檬酸量的增加,燃烧产物的晶化温度升高;过量柠檬酸添加改变了中间产物Fe的存在形式,促使γ-Fe_2O_3转化为热稳定性好的α-Fe_2O_3,进而使得W型钡铁氧体的成型温度升高,出现M晶型钡铁氧体。

Barium hexaferrite was synthesized by citric acid sol-gel process. The thermo gravimetric analysis （ TGA ）,Fourier transform infrared spectroscopy （ FT-IR ）, X-ray diffraction （XRD ） and scanning electron microscopy （SEM） were used to characterize the crystal phase of calcination products with different citric acid additives.Results revealed that the crystal phase of barium hexaferrite was W-type when the value of n（CA）/n（MN）≤1. 2 ,and if n（CA）/n（MN）- 2, the crystal phase would change into M- type.With the increase of citric acid,the crystallization temperature of the product would rise. The excessive citric acid additive changed the existing form of Fe,which promoted the transformation from y - Fe2O3 to a - Fe2O3,which was more stable with the increase of formation temperature of the W-type barium hexaferrite,and the appearing of M- type.