宽温低损耗MnZn功率铁氧体研究

【作者】 刘治；

【导师】 兰中文；

【作者基本信息】 电子科技大学 ， 材料科学与工程， 2010， 硕士

【摘要】 本文采用氧化物陶瓷工艺制备MnZn功率铁氧体,主要研究了主配方、添加剂和成型工艺对MnZn功率铁氧体微结构、物相和磁性能的影响。首先,通过主配方研究发现,宽温低损耗MnZn功率铁氧体的适宜配方为Fe2O3:MnO:ZnO=52.5:35.5:12(mol%)。其次,研究了CaCO3-SiO2、ZrO2、Co2O3、Li2CO3添加剂对功率铁氧体物相、微结构和磁性能的影响。结果表明: CaCO3-SiO2添加剂主要富集于晶界,生成的另相并非通常所认为的CaSiO3,而是Ca2ZnSi2O7;随着CaCO3-SiO2含量的增加,晶粒的均匀性得到改善,但是过量添加则造成不连续生长,气孔率增加,导致磁导率先升高后降低,磁芯损耗则呈现相反的变化趋势,其适宜添加量为9×10-3wt%CaCO3+5.4×10-3wt%SiO2。随着ZrO2添加量的增加,晶粒尺寸逐渐增大,磁导率先升高后降低,磁芯损耗则呈相反的变化趋势,其适宜添加量为0.015wt%。当Co2O3添加量为0.175wt%时,功率铁氧体的平均晶粒尺寸较小,晶粒均匀,此时磁导率最大,磁芯损耗最低,且对磁滞损耗的降低作用甚是显著。合适的Li2CO3添加剂可以提高铁氧体密度,使晶粒变得均匀,降低损耗,促使磁导率温度曲线二峰向高温移动,其适宜添加量为0.02wt%。然后以上述部分添加剂为基础添加剂进行正交实验,结果表明,最佳添加剂组合为V2O50.02wt%、ZrO20.018wt%、Ta2O50.04wt%。随着成型压力的增大,烧结样品的密度先增大后减小,磁导率呈增大趋势,损耗的变化较小,最佳成型压力为60MPa。最后,将制得的宽温低损耗MnZn功率铁氧体在宽温宽频范围内进行损耗分析得出,MnZn铁氧体磁滞损耗和涡流损耗随着温度的升高,先下降后上升;磁滞损耗和涡流损耗随着频率的升高而升高;当频率高于300kHz时,剩余损耗开始出现,且随温度和频率的升高,剩余损耗逐渐增大。各种损耗在总损耗中的比重随着温度和频率的变化,发生很大变化。更多还原

【Abstract】 Low loss MnZn power ferrites in wide temperature were prepared by conventional oxide ceramic process. It mainly researched the influences of compositions, additives and the pressure on the composition phase, microstructure and magnetic property.First, the effects of three oxide compositions were studied. In the main compositions research, the proper molar ratio of three oxide compositions is Fe2O3: MnO: ZnO= 52.5: 35.5: 12(mol%). Second, The effects of CaCO3-SiO2 , ZrO2, Co2O3, Li2CO3additives on the microstructure and magnetic properties in MnZn ferrite were studied. The results show that: CaCO3-SiO2 dopants segregate in the grain boundary, forming a new phase Ca2ZnSi2O7, which is different from commonly view CaSiO3. As the CaCO3-SiO2 additives increase, the microstructure is improved, but the excessive additives lead to exaggerated grain growth. An initial increase followed by a subsequent decrease of initial permeability is observed. However, the core loss changes contrarily. The proper additives are 9×10-3wt%CaCO3+5.4×10-3wt%SiO2. With the increase of ZrO2 addition, the average grain size increases monotonously, an initial increase followed by a subsequent decrease of permeability is observed, while the total loss, hysteresis loss and eddy loss change contrarily. When doped 0.015wt%ZrO2, the synthesize characteristic is the best. When the Co2O3 additive at 0.175wt%, the average grain size is small and homogeneous. The initial permeability is the highest and the loss is the lowest. And its improvement to hysteresis loss is bigger than eddy current loss. Proper additive Li2CO3 can increase the density, makes the grain uniform, decreases the loss. With the increase of additive, the second peak of permeability moves to high temperature. Then make parts of them as the based additives. The orthogonal experimental results show that: the best additives combination are V2O50.02wt%, ZrO20.018wt%, Ta2O50.04wt%. With the molding pressure increase, the sintered sample density and the permeability first increase and then decrease, but the loss changes little. Last, the low loss ferrite’s loss properties in a wide temperature and frequency range were studied. With the increase of frequency, the hysteresis loss and the eddy current loss increase. When the frequency≥300kHz, the residual loss appeares. The residual loss increases with increasing temperature and frequency. The ratios of the hysteresis loss, eddy loss and residual loss in total loss change greatly with the various of temperature and frequency.更多还原