Investigation Of Doping And Heat Treatment Effects On The Properties Of Low Loss Ferrite For High Frequency Applications

The development of electromagnetic devices requires continuous improvement of circuit design and performance of material components as well as the manufacturing process.Variety of different magnetic materials are developed in last few decades with improving efficiency and reduction of cost.Soft ferrites exhibit high electrical resistivity,high initial permeability,low eddy currents,low dielectric constant,moderate saturation magnetization,coercivity and permittivity.Soft ferrites are used in all current day appliances and modern technologies,including telecommunication,electronic engineering,Sensors,biomedical,catalysis,water treatment and rechargeable batteries.Therefore,in ferrite manufacturing,both composition and process conditions are very critical to achieve the required quality.The growing demands for lighter and smaller components,capable to operate at high-frequency,focused research on the soft magnetic materials that offers low power loss and better performance.MnZn ferrites capable to operate at 3-5 MHz frequencies are prepared using solid state powder processing technique under an optimized sintering procedure and doping(CaO and Nb2O5).The effects of Co2O3,SnO2 and TiO2 doping are investigated on the magnetic properties,power loss and structural properties of MnZn ferrites.1)The effects of Co2O3 and SnO2 doping on the properties of MnZn ferrites are investigated.The doping improves the magnetic properties and reduces the power losses.Co2O3 doping increases the temperature and frequency stability of frequency and power losses.The minimum power loss for sample Col doped with 1000 ppm of Co2O3 is 59 kW/m3 ?,10 mT for 3 MHz and highest permeability is 792.SnO2 doping also results in the decrease of power losses.The sample doped with 1000 ppm of SnO2 shows minimum power losses of 84 kW/m3 and 220 kW/m3 at 20 ? and 100 ? respectively.However,the samples doped with SnO2 lacks the temperature stability of power losses as observed for Co2O3 doped MnZn ferrite samples.2)The effects of Co2O3 and SnO2 co-doping on the properties of MnZn ferrites resulted in a sharp decrease of eddy-current loss and residual loss of the MnZn ferrites at 3-5 MHz and improved the temperature characteristics at 20-120 ?.The minimum power losses at 20 ?,10 mT for 3 MHz and 5 MHz are 20 kW/m3 and 81 kW/m3,while the power losses at 100 ?,10 mT for 3 MHz and 5 MHz are 60 kW/m3 and 205 kW/m3 respectively.The optimal saturation magnetic flux density and initial permeability are 480 mT and 675 respectively.The cut-off frequency of the sample is 12 MHz,establishing it as an ideal material for high-frequency applications.3)The effect of TiO2 doping on the magnetic and power loss properties of MnZn ferrites are investigated.Sample doped with 1500 ppm of TiO2 gives minimum power loss Pcv(min)of 47 kW/m3 and maximum magnetic induction of BS of 510 mT.The permeability of sample is 915.The effect of co-doping results in temperature stability of ferrites.4)Structural,dielectric and magnetic properties of single-phase cobalt ferrite nanoparticles,synthesized by co-precipitation method and annealed at different temperatures,is investigated.The average crystallite size increases from 20 nm to 60 nm with annealing temperature.Meanwhile,the shape of nanoparticles is also changed from spherical to octahedron and then cubic.The ac conductivity is decreased with increase of crystallite size.The saturation magnetization is increased from 59 emu/g to 81 emu/g and coercivity is dropped from 1316 Oe to 428 Oe with the increase of particle size.Cobalt ferrite is one of the best soft materials with better catalytic,sensing as well as many other microelectronics applications.