Preparation And Properties Of Low Temperature The Sintering Nicuzn Ferrite Powder

Ferrites are important magnetic functional materials which are used in many fields. The synthesis of the powder has always been the subject of extensive studies. In this paper, the spinel ferrites were synthesized with different methods. The synthesizing conditions, structure and magnetic properties were groped. The structure was characterized by XRD, LPS, SEM. The magnetic properties were tested by VSM and HP4294A.In the part of theoretical analysis, through thermodynamic analysis for different Men+ions in different systems, the [Men+] concentration as a function of pH value was obtained, and hence the pH window of complete co-precipitation for various Men+ions was determined. The results shows that Ni2+, Cu2+and Zn2+ions are difficult to completely co-precipitate in a system containing NH3 because of their strong complexing ability with NH3, while they can co-precipitate entirely with NaOH as precipitant at a pH value of 10-11.In the part of experiments investigations, the preparation conditions of precursor were studied and the NiCuZn ferrite powder with small grain size and excellent performance were prepared by precursors pre-burning method and direct oxidation process.The synthetic temperature of precursor and stirring rate as well as charging rate of salt solution were researched.Results show that average particle sizes of precursor and oxidative material are minished and the corresponding pre-burned material size have the growing tendence as the reaction temperature rise.When synthetic temperature of precursor at 70℃,the average particle sizes of precursor is about 3μm and that of the corresponding oxidative material is only 2.5μm.With the charging rate of salt solution increase, the average particle sizes of the precursor and pre-burning materials as well as the oxidation are expected to increase. The uniform tendence is obtained between the effects of changement of rotational speed on precursor and on pre-burned materials, that's the average particle sizes of the precursor and pre-burning materials are minished as the increasement of rotational speed, while the effects on oxidative material are opposite.The introduction of three different types of dispersant,that's LAS, polyvinylpyrrolidone (PVP) and polyacrylic acid (PAA), the appropriate dispersant agent is selected and the optimal dosage of that is determined. Results show that when reaction temperature is at 50℃and the stirring rate is 1000rpm as well as the flowing velocity of salt solution is 2.5ml/min and addtion of LAS is 1%, the fast sedimentation rate of precursor and direct oxidation slurry is appeared and that easy to wash,in additional, grain size of powder is small,the average particle size of that is about 1μm to 3 tμm.Presintering temperature of precursor pre-burning method and sintering temperature were studied.When the pre-firing temperature was at 850℃, the average particle size was about 2μm and the proportional saturation magnetization was 62 emu/g for the largest. The relative density, initial permeability, cut-off frequency were 0.8, about 90,59MHz respectively when sintering temperature is at 950℃.Grains of NiCuZn ferrite powder which was prepared use direct oxidation method were small.Average grain sizes were only around 10nm and the average particle sizes were less than 3μm.Slurry of precursor presented weak magnetic, paramagnetic characteristic curves appeared in magnetic hysteresis loop, the proportional saturation magnetization was 11emu/g after oxidized for 5h. The relative density, initial permeability of sample, cut-off frequency were 0.92,25,more than 110MHz respectively after sintering at 850℃.