磷酸浓度对Fe-6.5%Si磁粉芯组织及磁特性的影响

通过扫描电子显微镜(SEM)、X射线衍射仪(XRD)、差示扫描量热仪(DSC)、傅里叶红外光谱仪(FTIR)、综合物性测量系统(PPMS)及软磁交流测量装置对Fe-6.5%Si磷化粉末及其磁粉芯的结构和磁特性进行分析。结果表明:在不同的磷酸浓度条件下,粉末表面均可获得覆盖均匀的Fe PO4薄层;磷化粉末在550℃左右发生Fe PO4晶化反应,在1 000℃左右发生SiO_2合成反应。随磷酸浓度增加,包覆层厚度从3~5μm增加到10μm左右,粉末的饱和磁化强度逐渐降低;磁粉芯600℃退火后的物相结构为α-Fe(Si),Fe PO4,Fe_2O_3混合相,其微观应变在磷酸浓度为0.15 g/m L时达到最低值;随磷酸浓度增加,磁粉芯有效磁导率下降,而总损耗、磁滞损耗和涡流损耗均呈先降低后升高的趋势,在0.15 g/m L磷酸浓度时达到最低。

Effects of phosphate concentration on the structure and magnetic properties of Fe-6.5%Si magnetic powder cores

The microstructure and magnetic properties of Fe-6.5%Si phosphate powder and powder cores were analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), fourier transform infrared spectroscopy (FTIR), physical property measurement system (PPMS) and soft magnetic alternating current measurement device. The results show that the thin FePO4 layer is coated uniformly on the powder surface under different phosphate concentrations. The reactions of FePO4 crystallization and SiO2 synthesis occur at 550℃and 1 000℃, respectively. With increasing phosphate concentration, the thickness of coating layer increases from 3~5μm to 10μm and saturation magnetization of phosphatized Fe-6.5% Si powders decreases. The powder cores possesses α-Fe(Si), FePO4 and Fe2O3 phases after annealing at 600℃, and the microstrain of powder cores with phosphate concentration of 0.15 g/mL is the lowest. With increasing phosphoric concentration, the effective permeability of powder cores decrease, while the total loss, hysteresis loss and eddy current loss decrease firstly and then increase, and reach the minimum value at 0.15 g/mL.