Synthesize And Research The Magnetic Properties Of NiZnFe₂O₄ Particles

Spinel ferrite is a kind of classical magnetically soft material. Because of unique structure and performance, it was extensive used in many aspects, such as sensor element, photo electric materials, magneto sensor, photo recording material, coloring agent, dehydrogenation catalytic and so on. At the present time, the preparation method of spinel ferrite principal focusing on tradition dry method and wet chemical method. Conventional methods of prepared of M^â…¡M₂^â…¢O₄ spinel have some disadvantages. According to the fact that high-temperature calcined of LDHs lesds to a mixture of M^â…¡M₂^â…¢O₄ spinel and M^â…¡O. We synthesize LDHs containing magnetic ion Ni^2＋,Mg^2＋,Co^2＋,Fe^2＋and non-magnetic ion Zn²⁺ in the layer. The calcinations of the LDHs afford a mixture of M^â…¡M₂^â…¢O₄ spinel by control of content of metal ion in the layer. Making use of this special property of LDHs precursor, the thesis describes a systematic study mainly fousing on the preparation of LDHs crystal structure,thermal stability and the calcined products crystal structure and magnetic properties. The calcinations of the LDHs lead to the formation of M^â…¡M₂^â…¢O₄ ferrite with excellent magnetic properties. 1．The synthesis of NiZnFe₂O₄,CoFe₂O₄,MgFe₂O₄ spinel by calcined M^â…¡Fe(â…¡)Fe(â…¢)-SO₄^2--LDHs precursors.We synthesize the NiZnFe₂O₄ by calcined M^â…¡Fe(â…¡)Fe(â…¢)-SO₄^2--LDHs precursors, researched NiZnFe₂O₄ precursors and spinels have single phase transformation and strong magnetic performance. At the same time , we synthesize CoFe₂O₄,MgFe₂O₄ spinel by this method, and researched precursors and spinels phase and magnetic performance. The result found calcined M^â…¡Fe(â…¡)Fe(â…¢)-SO₄^2--LDHs precursors can synthesize well performance spinel.2．The synthesis of NiZnFe₂O₄ spinel by calcined NiZnFe(â…¡)Fe(â…¢)-SO₄^2--LDHs precursors.Making use of LDHs chemical constitution controllability, we synthesize LDHs containing magnetic ion Ni²⁺,Fe²⁺,Fe²⁺ non-magnetic ion Zn in the layer. NiZnFe(â…¡)Fe(â…¢)-SO₄^2--LDHs have been prepared from Ni,Zn and Fe(â…¡) precursors by coprecipitation method. The structure and thermal stability of NiZnFe(â…¡)Fe(â…¢)-SO₄^2-LDHs have been investigated. The calcinations of NiZnFe(â…¡)Fe(â…¢)-SO₄^2-LDHs leads to NiZnFe₂O₄ spinel. All the samples of NiZnFe₂O₄ appeared diffraction maximum of spinel ferrite research by X-ray. Through the magnetic properties research single magnetic domain quality magnetic performance were found in the samples. At the same time, the cut-off frequency of spinels calcined by LDHs increasing, and deterioration reducing with decreasing of Zn²⁺ molar ratio. The dielectric constant ofNiZnFe₂O₄ unconverted with the frequency in low-frequency and highfrequency. It showed that calcinations products express better dielectricstailization.3．The synthesis of CoFe₂O₄ spinel by calcinedCoFe(â…¡)Fe(â…¢)-SO₄^2--LDHs precursors.We synthesis the CoFe₂O₄ spinel by calcinedCoFe(â…¡)Fe(â…¢)-SO₄^2-LDHs, researched CoFe₂O₄ precursors andspinels phase transformation and magnetic performance in detail. Byexperiment found, the phase structure influenced by the content of Co²⁺molar ratio. When Co²⁺/Fe²⁺/Fe²⁺ molar ratio is 3/5/2, calcinstion productis single phase spinel. When Co²⁺/Fe²⁺/Fe³⁺ molar ratio is 1/3/1, thesample is a mixture CoFe₂O₄ and Fe₂O₃．When Co²⁺/Fe²⁺/Fe³⁺molar ratiois 1．92/1/2 and 3/1/1, the calcination products are mixture CoFe₂O₄ andCoO. It is helpful enhance saturation magnetiation with increase the Co²⁺molar ratio in some level. Complex magnetic permeability and dielectriccoefficient of calciantion products were stability with changing offrequency.