Study On Structure,Magnetism And Gas-Sensitive Properties Of Ni-Zn-Co Ferrite

As an important part of the design and preparation of multifunctional materials,multi-component nanocrystalline ferrites have been widely used in the fields of high-density magnetic recording,magnetic fluid,catalyst,drug delivery and microwave absorption.Ni-Zn-Co ferrite has excellent magnetic properties and temperature sensitivity,and has potential applications in heat exchangers,semiconductor devices,and gas sensors.In this paper,the Ni-Zn-Co ferrite magnetic materials can be prepared simply,quickly and economically by sol-gel method.The effects of different conditions on the microstructure,magnetic properties and gas sensitive properties of the Ni-Zn-Co ferrite materials are studied by means of metal cation substitution,rare earth ion doping and heat treatment at different temperatures.Three goals listed below are primarily completed by this paper:1.At room temperature,Ni_xZn_1-x-yCo_yFe₂O₄（x=0.0 y=0.0,x=0.8 y=0.0,x=1.0y=0.0,x=0.0 y=0.8,x=0.0 y=1.0,x=0.4 y=0.4）was synthesized using the sol-gel technique.X-ray diffraction（XRD）results show that the lattice structure of the sample is spinel type without other impurity phases.The spinel structure of the sample was reconfirmed by Fourier transform infrared spectroscopy（FTIR）,and the completeness of the preparation process and functional group information were evaluated.Scanning electron microscopy（SEM）showed that the samples with spherical and cubic shapes were agglomerated due to magnetism and sintering at high temperature.The particle size distribution is narrow and the sample size is uniform.The element composition of the prepared sample can be determined by energy spectrum（EDX）.The vibrating sample magnetometer（VSM）can measure the hysteresis loop of the sample at room temperature,and the magnetic characteristics and related magnetic parameters of the sample can be obtained from the figure.In the process of characterization,pure nickel,zinc and cobalt ferrites were used as control groups to analyze the changes in structure and properties of ferrites composed of them.2.Sm³⁺doped nickel-zinc-cobalt spinel ferrites were prepared by sol-gel method.The chemical formula is Ni_0.2Zn_0.1Co_0.7Fe_2-xSm_xO₄.The doping amount x ranges from 0to 0.1,and the doping amount change step is 0.025.By X-ray diffraction pattern,the structure of the sample was determined to be cubic spinel type.When the doping amount x≥0.05,the impurity phase Sm Fe O₃appeared.Fourier transform infrared spectroscopy can reveal the information of the atomic groups that can indicate the chemical properties of the sample.The elastic modulus and bond length vary identically with the doping amount.By means of scanning electron microscope and transmission electron microscope,the morphology of the samples is spherical and cubic.The polycrystalline structure and pore characteristics of the samples were revealed by the images.Energy dispersive spectrum shows that the elements contained in the sample are consistent with the chemical formula and there are no other impurity elements.The hysteresis loops at room temperature measured by VSM show the soft magnetic properties of the sample.The core-surface model shows that the magnetization decreases with the increases of grain size.Coercivity values are related to domain wall displacement and domain wall rotation.According to the differential diagram of magnetization curve,the domain structure characteristics of samples can be judged.3.In this experiment,Ni_0.2Zn_0.1Co_0.7Fe₂O₄ferrite powders were prepared at different annealing temperatures（room temperature,100℃,300℃,500℃,700℃and 900℃）.The experimental method used was sol-gel.The crystallinity of the sample,as well as the spinel structure of the sample can be obtained by XRD.The effects of structural changes on lattice constants,average crystal size,porosity and other structural parameters were also analyzed.The integrity and functional group information of the preparation process were evaluated by FTIR.The morphological characteristics of samples can be analyzed by SEM.The EDX diagram shows the elemental compositions of the samples.In addition,the mechanism of gas sensitivity shows that multi-component spinel ferrites can be used to prepare long-term stable Et OH sensors.VSM was used to analyze the magnetic properties of the samples,and the relationship between coercivity,magnetization,average grain size and anisotropy of magnetic crystals was determined.When the annealing temperature is 300℃,the sample has a maximum coercivity value of 936.24 Oe.This experiment provides a valuable direction for the fabrication of low-cost catalyst,magnetic recording media,and sensors.