质子转移对低热法制备SrFe_(12)O_(19)结构和性能的影响

Effect of Proton Translocation on Microstructure and Magnetic Properties of SrFe_(12)O_(19) Synthesized by Low-heating Solid-state Reaction

以Fe(NO3)3·9H2O、Sr(NO3)2和C6O7H8为原料,NH3为质子转移剂,在不同pH值条件下,进行低热固相反应,制备出系列前驱体,经900℃灼烧后得到相应产物。采用XRD、SEM和VSM对产物进行表征。结果表明,合成出的产物为平均粒径约100 nm的SrFe12O19纳米粉体。并发现随着pH值从6增加到11,合成产物的XRD衍射峰出现峰值先变大后变小现象;3种晶格参数(a,c,Vcell)出现先减小,后增大规律,而结晶度Xc则先变大,后变小。在pH=10时,所对应的晶格参数均发生最大拐点变化,因此产物的磁性能表现最佳(Ms=51.4 A·m2/kg、Mr=29.5 A·m2/kg、Hc=71.2 A/m),表明磁性粒子表面在此条件下磁交换作用最强。

The serial precursors were prepared by the low-heating solid-state reaction with Fe（NO3）3·9H2O, Sr（NO3）2, C6O7H8 as reacting reagents and NH3 as a reagent of proton translocation at different pH values, and as-synthesized samples were obtained under the condition of calcining at 900 ℃. The samples were characterized by XRD, SEM and VSM. The result indicates as-synthesized samples are nano-SrFe12O19 powders with the crystallite size of about 100 nm. The diffraction peak intensity of samples is firstly from weak to strong, and then from strong to weak. The values of three crystal parameters （a, c, Vcell） all have the same change, from great to small, and then from small to great, while the value of degree of crystallinity is from great to small. With pH=10, the corresponding lattice parameter changes all at the biggest turning point, so that the samples have the best magnetic properties （Ms=51.4 A·m2/kg, Mr=29.5 A·m2/kg, Hc=71.2 A/m）, which indicates magnetic exchange interaction is strongest on the particle surface.