显微组织对NiCuZn铁氧体磁导率温度特性的影响

Effects of microstructure on temperature dependence of permeability of NiCuZn ferrites

采用传统氧化物法制备了具有(Ni0.27Zn0.64Cux)Fe1.98O4(x=0.1,0.2)成分分子式的NiCuZn铁氧体,通过调整成分和改变烧结温度获得具有不同显微组织的铁氧体样品,并研究了其显微组织对磁导率温度稳定性的影响.结果表明:晶界气孔会产生较大退磁场,由于该退磁场对温度变化不敏感,可增强总有效各向异性场的温度稳定性,从而改善铁氧体磁导率的温度稳定性;然而,晶粒内部的气孔对铁氧体磁导率的温度稳定性会产生显著的恶化影响,其原因在于:在磁化过程中,晶粒内部气孔对畴壁移动具有很强的钉扎效果,会减少壁移磁化对铁氧体磁导率的贡献.与壁移磁化磁导率相比,畴转磁化磁导率对温度变化更为敏感.铁氧体晶粒内部气孔数量越多,铁氧体磁导率的温度稳定性就越差.

Ferrites with compositions of（Ni0.27Zn0.64Cux）Fe1.98O4（x=0.1,0.2）were prepared using conventional ceramic methods.Samples with different microstructures were obtained by adjusting the composition and sintering temperature.The relationship between the microstructure and the temperature dependence of permeability was investigated.Results showed that the intergranular pores in the ferrites generate large demagnetizing fields.Due to the demagnetizing field is not sensitive to temperature,it can reduce the temperature dependence of the total effective anisotropy field and decrease the temperature dependence of permeability accordingly.However,the intragranular pores have significant negative impact on the temperature dependence of permeability,due to it pins the movement of domain walls.Compared with the permeability induced by domain wall motion,the permeability resulted from the spin rotation is more sensitive to temperature.As a result,the permeability of ferrites becomes more sensitive to temperature with increasing micropores within grains.