Controllable Synthesis And Magnetic Properties Of Spinel Mn-Zn And Ni-Zn Ferrite Nanocrystallines Via Soft Chemistry Method

In this paper, by using nitrate and hydrochloride as raw materials, Na OH as precipitant agent, spinel Mn-Zn and Ni-Zn series of magnetic nano ferrite were prepared by hydrothermal method and microemulsion method. Influence of the solution p H value,ω, reaction temperature, reaction time, the concentration of Na OH, composition ratio and rare earth elements doping on the microstructures and magnetic properties of the synthesized Mn-Zn and Ni-Zn nano ferrites have been studied. By through XRD, SEM and VSM measurements, the microstructures, morphology and magnetic properties of the as-synthesized nano ferrites were chatactered. The results obtained are as follows:(1) Mn-Zn and Ni-Zn magnetic nano ferrites were prepared by hydrothermal method, and process parameters have the following effects on the microstructures and the magnetic properties of the synthesized nano ferrites:a) p H value of the solution has the significant influence on the microstructures of the nano ferrites. With the increase of p H value,the concentration of OHincreased accordingly, and metal cation was precipitated completely and corresponding stoichiometric spinel nanometer ferrites were generated. As a result, the crystallinity of the nano ferrites has been improved.b) The reaction temperature and reaction time have a certain impact on the particle size of the samples. Raising the temperature and adding the time are beneficial to improve the crystallinity of the samples.c) Mnx Zn1-x Fe2O4 nanocrystals have the best crystallinity when Mn2+content is0.5. The crystallinity of Nix Zn1-x Fe2O4 nanocrystals are improved with the increase of Ni content.d) When the Gd3+doping concentration is low, the lattice of spinel Mn-Zn and Ni-Zn ferrite will not be changed whereas the doping concentration is too high,the lattice of the spinel ferrite has been destroyed, and the Gd3+ can not entered into the spinel lattice, resulted in the inpure phase.e) When the doping concentration is 0.02, the obtained nano ferrite i.e.Mn Fe1.98Gd0.02O4 posseses the highest saturation magnetization(σs), which is about 67.2 emu/g.(2) Mn-Zn and Ni-Zn magnetic nano ferrites were prepared by microemulsion method, and process parameters have the following effect on the microstructures and magnetic properties of the as-synthesized nano ferrite:a) The concentration of NaOH has an important influences on the microstructures and the crystallinity of the nano ferrites. In the selected range of the Na OH concentration, with the increasing of [OH-], the grain size of the samples increases significantly, and the crystallinity of the samples is improved accordingly.b) The ratio of surfactant to water(ω), reaction temperature and reaction time has little influences on the microstructures of the synthesized nano ferrites.c) The crystallinity of Mnx Zn1-x Fe2O4 and Nix Zn1-x Fe2O4 nanocrystals decreases with the increasing of proportion of divalet ions(i.e. Mn2+, Zn2+or Ni2+). The obtained doped nano ferrite i.e. Ni0.7Zn0.3Fe2O4 has the highest saturation magnetization(σs), and the σs is about 41.11 emu/g.d) The doping of Ho3+has little impact on the grain size of the Mn-Zn and Ni-Zn nano ferrites. Whereas when the doping concentration of Ho3+ is too high, the lattice of the spinel ferrite has been destroyed, and the Ho3+ can not into the lattice and result in inpure phase.