Ti-Substituted BaFe12O19 Single Crystal Growth and Characterization

Ti-substituted barium hexaferrite BaFe12O19 single crystals BaFe12–xTixO19 with x up to 1.3 and sizes 2–8 mm were grown by spontaneous crystallization from molten sodium carbonate flux. The distribution of Ti on different crystallographic sites was determined from single crystal X-ray diffraction data. For low Ti contents up to x = 0.8 the unit cell expands; on further increase of the Ti amount the unit cell starts to shrink. This behavior for low Ti contents is most likely due to a reduction of Fe3+ to Fe2+ for charge balance. At higher Ti concentrations, supposedly vacancies in the transition metal substructure are formed. An increasing Ti concentration results in a monotonous reduction of the Curie temperature from 452 to 251 °C and the saturation magnetization at room temperature from 64.8 to 24.8 emu/g for powder samples and from 70.0 to 60.1 emu/g for single crystals (for x up to 0.78).

通过熔融碳酸钠熔剂自发结晶法，制备了钛取代钡六铁氧体（Ti-substituted barium hexaferrite）BaFe₁₂O₁₉单晶，其化学式为BaFe₁₂–ₓTiₓO₁₉，x最高可达1.3，晶体尺寸介于2~8 mm之间。借助单晶X射线衍射（single crystal X-ray diffraction）数据，明确了钛在不同晶体学位点的分布情况。当钛含量不超过x=0.8时，晶胞发生膨胀；随着钛含量进一步提升，晶胞则开始收缩。这种低钛含量下的晶胞膨胀现象，大概率是为维持电荷平衡，Fe³⁺被还原为Fe²⁺所导致的。当钛浓度更高时，推测过渡金属亚结构中会出现空位。随着钛浓度持续升高，居里温度（Curie temperature）从452 ℃单调降至251 ℃；室温下的饱和磁化强度（saturation magnetization）也随之下降：粉末样品的饱和磁化强度从64.8 emu/g降至24.8 emu/g，而x最高为0.78的单晶样品则从70.0 emu/g降至60.1 emu/g。