【作者】 刘颖；

【导师】 张密林；

【作者基本信息】 哈尔滨工程大学 ， 材料学， 2007， 博士

【摘要】 M-型钡铁氧体是一类具有广泛应用前景的磁性功能材料,为了获得高性能的铁氧体粉料,其制备方法和性能调控一直是研究的热点。本文分别采用不同的方法合成M-型钡铁氧体纳米材料,以共沉淀-熔盐法的最佳工艺条件合成了系列掺杂M-型钡铁氧体。通过X射线衍射仪（XRD）、扫描电子显微镜（SEM）、振动样品磁强计（VSM）等手段对样品进行表征,并进行细致的研究。柠檬酸sol-gel法、共沉淀法是具有许多优点的通用方法。本文研究了柠檬酸sol-gel法、共沉淀法及共沉淀-熔盐法合成BaFe₁₂O₁₉。研究发现,共沉淀法在700℃合成了BaFe₁₂O₁₉,比sol-gel法具有更低的合成温度,这主要是由于中间相的出现引起的。通过引入助熔剂,对共沉淀法改进,能够获得分散性提高的六角片状单磁畴BaFe₁₂O₁₉微粉。同时,助熔剂种类、煅烧时间和温度都对样品有影响。磁性能优良的BaFe₁₂O₁₉,在100%KCl为助熔剂的情况下,通过共沉淀-熔盐法,在450℃2h+950℃4h煅烧合成,比饱和磁化强度达到71.9 A·m²/kg,接近钡铁氧体比饱和磁化强度的理论值72 A·m²/kg,矫顽力367.8kA/m,剩磁43.4 A·m²/kg,最大磁能积12.2 kJ·m^-3。通过共沉淀-熔盐法制备了CO²⁺、Zn²⁺、Mn²⁺与Sn⁴⁺或La³⁺二元或三元联合取代的M-型钡铁氧体,随取代量x增加,均引起样品晶胞参数的增大,样品粒子尺寸变小。CO²⁺、Zn²⁺、Mn²⁺分别与Sn⁴⁺元联合取代BaFe₁₂O₁₉时,随掺杂浓度增加,矫顽力和矫顽力温度系数均减小,比饱和磁化强度发生了不同的变化。在低掺杂浓度时,CO²⁺、Mn²⁺掺杂有利于比饱和磁化强度增加,Zn²⁺引起了比饱和磁化强度的降低。高浓度掺杂时,比饱和磁化强度均降低,CO²⁺、Zn²⁺掺杂引起的比饱和磁化强度降低更快。对于BaFe_122xZn_x/2Co_x/2Sn_xO₁₉样品,随取代量x增加,比饱和磁化强度、比剩余磁化强度、最大磁能积、矫顽力均降低。对于BaFe_122xZn_x/2Co_x/2Sn_xO₁₉样品,随x增加比饱和磁化强度先增加后减少,但都高于BaFe₁₂O₁₉。替代量x在0.5-0.6之间的钡铁氧体磁粉,不仅比饱和磁化强度高,矫顽力温度系数低,而且矫顽力的大小在80-240 kA·m^-1之间。这种磁粉有希望在高密度磁记录介质方面得到应用。对于Ba_1-xLa_xFe_12-xMn_xO₁₉和Ba_1-xLa_xFe_12-xCo_xO₁₉增大,K₁、H_A、H_c均先增加后减少,但比饱和磁化强度变化不同,前者几乎没有改变,后者的比饱和磁化强度也表现为先增加后减少。由此可见,La³⁺离子掺杂能够有效提高钡铁氧体的矫顽力,因此可作为制备M-型钡铁氧体永磁材料和调控M-型钡铁氧体磁记录介质矫顽力的有效的掺杂元素。通过CO²⁺、Mn²⁺、Sn⁴⁺、La³⁺联合取代,有望获得性能更优异的高密度磁记录介质。更多还原

【Abstract】 M-type barium ferrite is magnetic functional material with wide potential applications. The investigation has focused on the new synthesis methods and modification on the characters in order to obtain good performance M-type barium ferrite. In this paper, M-type barium ferrite particles were synthesized via different methods, in which the better method was established to prepare the series doped samples. These materials were characterized by XRD, ESEM and VSM, and then studied in detail.Sol-gel method and co-precipitation technique are usual methods with many advantages. In this paper, BaFe₁₂O₁₉ particles were prepared by sol-gel, co-precipitation, coprecipitation-reflux methods, respectively. BaFe₁₂O₁₉ particles were obtained by calcining only at 700℃for co-precipitation technique, lower than the temperature used in Sol-gel method. Dispersible like-plate hexagonal BaFe₁₂O₁₉ particles were synthesized by coprecipitation-reflux method originating from modified co-precipitation technique. Using the method, the properties of the samples were affected on by the kinds of flux, different calcined time and temperature. When 100% KCl acted as reflux,BaFe₁₂O₁₉ particles were prepared by calcining at 450℃for 2hs and then at 950℃for 4hs in coprecipitation- reflux method. BaFe₁₂O₁₉ particles had 71.9 A·m²/kg of specific saturated magnetization （Ms） near the theoretical value, and 367.8kA/m of coercivity.Co²⁺, Zn²⁺, Mn²⁺, Sn⁴⁺ and La³⁺ doping M-type barium ferrite, BaFe_12-2xR_xSn_xO₁₉(R:Co²⁺, Zn²⁺, Mn²⁺) and Ba_1-xLa_xFe_12-xR_xO₁₉(R:Co²⁺,Mn²⁺) series samples were prepared by coprecipitation-reflux method. With increasing of substitution content x, lattice parameters increased, and particle sizes decreased. When R was Co²⁺, Zn²⁺ and Mn²⁺, respectively, coercivity and coercivitytemperature coefficient of BaFe_12-2xR_xSn_xO₁₉ decreased with increasing of substitution content x. On the other hand, Co²⁺ and Mn²⁺ doping contributed to improving Ms, while Zn²⁺ doping resulted in decreasing Ms at relative low x.Unfortunately, Ms and Coercivity of BaFe_12-2xZn_x/2Co_x/2Sn_xO₁₉ yet decreased with increasing of x so that BaFe_12-2xZn_x/2Co_x/2Sn_xO₁₉ was fail to be applied as the potential magnetic recording medium. For BaFe_12-2xMn_x/2Co_x/2Sn_xO₁₉ samples, Mswas higher than 72 A·m²/kg of theoretical value. The curve of Ms vs substitution content x had a crest at x=0.4, and Ms of BaFe_11.2Mn_0.2Co_0.2Sn_0.4O₁₉ was 78.4 A·m²/kg. When x was in the range from 0.5 to 0.6, M-type barium ferrite was potential high- density magnetic recording medium due to its high specific saturated magnetization, low temperature coefficient of coercivity and moderate coercivity from 80 to 240 kA·m^-1.For Ba_（1-x）La_xFe_（12-x）Mn_xO₁₉ and Ba_（1-x）La_xFe_（12-x）Co_xO₁₉,coercivities decreased with increasing of x.On the other hand, Ms of the former had little change, and Ms of the later firstly increased and then decreased. It could be concluded that La³⁺ dopant contributed to improving the coercivity of barium ferrite.更多还原