Abstract
NiCuZn Ferrites are widely employed for many electronic applications, but can be replaced by MgCuZn ferrites owing to their superior properties like high initial permeability, high resistivity, low magnetostriction, environmental stability and low cost. Three series of NiMgCuZn ferrites were prepared by conventional sintering process. The formation of single phase in these ferrites was confirmed by x-ray diffraction. Initial permeability measurements on these samples were carried out in the temperature range of 30-400℃. The effect of the external applied stress on the open magnetic circuit type coil with these ferrites was studied by applying uniaxial compressive stress parallel to magnetizing direction and the change in the inductance was measured. The variation of ratio of inductance (ΔL/L)% increases upto certain applied compressive stress and there after it decreases, showing different stress sensitivities for different compositions of ferrites studied in the present work. With a view to develop stress insensitive NiMgCuZn ferrite, a low stress sensitivity composition among all the ferrites studied was chosen and different amounts of SiO2 were added to it and a series of ferrite compositions were prepared. The variation of ratio of inductance (ΔL/L)% with external applied compressive stress was examined. These results show that, in a particular composition of 0.05 wt% SiO2added Ni0.3Mg0.3Cu0.1Zn0.3Fe2O4 ferrite exhibited stress insensitivity. It was noticed that addition of SiO2 was found to be effective in reducing the stress sensitivity. This was confirmed from the elastic behaviour studies at room temperature on these ferrite samples. These studies were carried out to develop a ferrite composition for its use as core material for microinductor applications.
Highlights
Microminiaturization of electronic circuits especially in the fields of mobile communication and information technology demands electronic components with very small size [1]
NiCuZn Ferrites are widely employed for many electronic applications, but can be replaced by MgCuZn ferrites owing to their superior properties like high initial permeability, high resistivity, low magnetostriction, environmental stability and low cost
The variation of ratio of inductance ( L/L)% with external applied compressive stress was examined. These results show that, in a particular composition of 0.05 wt% SiO2 added Ni0.3Mg0.3Cu0.1Zn0.3Fe2O4 ferrite exhibited stress insensitivity
Summary
Microminiaturization of electronic circuits especially in the fields of mobile communication and information technology demands electronic components with very small size [1]. An external compressive stress around 1000 kg/cm is produced on the core during hardening of the resin [18] This results in decreased values of inductance. Internal tensile stress inside the grains resulting from a difference in thermal expansion coefficients, causes in stress sensitivity, when a grain boundary phase occurs with a thermal expansion coefficient larger than that of the grains, tensile stress are produced inside the grains under cooling conditions Such tensile stress cancels external compressive stress to some degree. Complex addition improves stress insensitivity, but it improves flat temperature dependence of inductance which is very important for inductors In view of this in this laboratory the stress sensitivity of a series of NiCuZn ferrites for their use as micro-inductor core materials was studied and achieved the stress insensitivity in those ferrites [19] and could produce stress insensitivity by adding suitable additives. In the present investigation three series of NiMgCuZn ferrite and temperature variation of initial permeability and stress sensitivity of inductance were studied
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