Wide Temperature Low Loss Mnzn Power Ferrite Research

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.