本文采用固相反应法制备了掺杂M型钡铁氧体BaFe10.2Sc1.8O19,并对其在烧结过程中的相变及磁性质做了一定的研究。结果表明,当烧结温度低于1000℃时,尖晶石相BaFe2O4和铁离子缺失的M型铁氧体是主要的烧结产物。当烧结温度高于1050℃时,M型铁氧体BaFe10.2Sc1.8O19开始生成。直到当烧结温度达到1200℃时,BaFe10.2Sc1.8O19才以单相的形式存在于烧结产物中。随着烧结温度的升高,烧结产物的剩磁比和矫顽场逐步降低,并在烧结温度高于1200℃的时候降到接近于零。饱和磁化强度随着烧结温度的升高逐步升高,并在1050℃的时候达到最大值,随后逐渐降低。磁性质的变化过程与烧结产物的相变是一致的。以上结果表明,相对于Fe3+,Sc3+对M型铁氧体的掺杂需要更高的热能,并会导致M型铁氧体磁性质的较大变化。 Sc doped M-type hexaferrite BaFe10.2Sc1.8O19 was prepared with the conventional solid state reaction method. The phase and magnetic property transition processes in the sintering process of M-type hexaferrite BaFe10.2Sc1.8O19 have been investigated. Results show that the spinel phase BaFe2O4 and ion-deficient M-type hexaferrite dominate when sintering temperature is lower than 1000˚C. The M-type hexaferrite BaFe10.2Sc1.8O19 appears above 1050˚C and does not become a single phase until 1200˚C. Both the remanence ratio and coercivity of the samples decrease with increasing sintering temperature and drop to nearly zero above 1200˚C. However, the saturation magnetization of the samples increases with increasing sintering temperature until 1050˚C and then decreases. The magnetic property transition process agrees well with the phase transition process. The above results show that incorporation of Sc3+ into the M-type hexaferrite needs a higher thermal energy than that of Fe3+, and will lead to a drastic change in the magnetic properties of M-type hexaferrite.
M型铁氧体,Sc3+掺杂,烧结温度,相变,磁性质, M-Type Hexaferrite Sc3+ Substitution Sintering Temperature Phase Transition Magnetic PropertySc掺杂M型钡铁氧体烧结过程中的相变 及磁性研究
图4是室温下,烧结所得样品的磁性质随烧结温度的变化图。从图4(a)可以看出,样品的磁滞回线随烧结温度的变化发生了明显的改变。图4(b)表明样品的矫顽场(Hc)随烧结温度的升高而逐渐降低。具体的,当烧结温度低于1000℃时,Hc大于3000Oe,这也说明了此烧结温度下,硬磁材料BaFexO19 (10.2 ≤ x ≤ 12)是主要的烧结产物。当烧结温度高于1200℃时,Hc快速下降到约为0Oe,说明了固相反应的结束。M型铁氧体BaFe10.2Sc1.8O19和BaFexO19 (10.2 ≤ x ≤ 12)拥有类似的晶体结构,但磁结构却有很大差异。M型铁氧体BaFe10.2Sc1.8O19的磁晶各向异性常数接近于零,因此表现出软磁性。图4(c)表明样品的饱和磁化强度(Ms)开始随烧结温度的升高而逐渐增大,在1100℃时达到一个最大值,并在之后随烧结温度的升高而急剧降低。由于总的磁性原子数未发生改变,所以磁性的变化应该归因于烧结产物的相变。那么可以认为,Ms开始的增大是源于BaFexO19 (10.2 ≤ x ≤ 12)的生成,而之后的降低则是由于BaFe10.2Sc1.8O19的产生。有文献报道,非磁性Sc3+对Fe3+的取代会影响M型铁氧体中S、R、S*、R*界面处铁原子之间的交换作用,从而能够导致Ms的降低 [25] [26] 。Ms在1100℃时出现峰值更进一步说明了烧结温度在1050℃以上时,BaFe10.2Sc1.8O19开始形成。图4(d)表明样品的剩磁比(Mr/Ms)随烧结温度的升高而逐渐降低,其变化趋势和Hc相类似,进一步说明了M型铁氧体在Sc掺杂前后由硬磁性材料向软磁性材料的转变。
4. 总结
本文采用固相反应法制备了Sc3+掺杂M型钡铁氧体BaFe10.2Sc1.8O19,并对其在烧结过程(950℃~1250℃)中的相变及磁性质做了一定的研究。研究表明,当烧结温度低于1000℃时,尖晶石相BaFe2O4和离子缺失的M型铁氧体BaFexO19(10.2 ≤ x ≤ 12)是主要的烧结产物。当烧结温度高于1050℃时,Sc3+掺杂M型铁氧体BaFe10.2Sc1.8O19开始生成。直到当烧结温度达到1200℃时,BaFe10.2Sc1.8O19才以单相的形式存在于烧结产物中。随着烧结温度的升高,烧结产物的剩磁比和矫顽场逐步降低,并在烧结温度高于1200℃的时候降到接近于零。饱和磁化强度随着烧结温度的升高逐步升高,并在1050℃的时候达到最大值,随后逐渐降低。磁性质的变化过程与烧结产物的相变是一致的。磁性质的变化过程可以归因于烧结产物的相变以及Sc3+对M型铁氧体中Fe3+的取代。其中,Sc3+对Fe3+的取代会影响M型铁氧体中S、R、S*、R*界面处铁原子之间的交换作用,宏观上变现为Sc3+掺杂M型铁氧体磁性质的较大变化。
周 浩,汤如俊. Sc掺杂M型钡铁氧体烧结过程中的相变及磁性研究 Phase Transition and Magnetic Properties in the Forming Process of Sc Doped M-Type Hexaferrite[J]. 应用物理, 2016, 06(11): 265-271. http://dx.doi.org/10.12677/APP.2016.611033
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