Preparation And Characterization Of Nano-composite Of SrZn₂-W Ferrite And SrTiO₃

In the text, the development history and new progress of Microwave absorbing materials such as ferrite, ferroelectric and SrZn₂-W ferrite/SrTiO₃ nano-composite and typical preparation method of nano-materials were introduced. We have employed citric acid method to obtain W-type ferrite, SrTiO₃ and SrZn₂-W ferrite/SrTiO₃ nano-composite. Citric acid method as a solution-based method, which allows mixing of precursors at the molecular level, has an advantage in the preparation of ultra fine materials. In the citric acid method reagents are very simple, special equipment is not needed, Ion-substitutions can be easily introduced into the final product, and materials with high purity were synthesized.In this dissertation, we prepared the nano-materials by citric acid method. X-ray diffraction (XRD), Infrared (IR) spectroscopy, Vibrating simple magnetometer (VSM) and Transmission electron microscopy (TEM) were used to characterize the thermal decomposition behavior, the crystallization process, the particle size and morphology of the calcined powders. The major work is summarized as follows:(1) Effects of microstructures and magnetic properties in various conditions have been investigated. The amounts of citric acid, the water volume, pH value, calcination temperature and time were determined to prepare pure fine well-dispersed nano-SrZn₂Fe₁₆O₂₇ with citric acid method. We have obtained the best synthesis conditions.(2) Ion-substitutions can alter microstructures and magnetic properties of W-type ferrites to satisfy various requirements in different application realms. The specific saturation magnetization (Ms), the specific remanent magnetization (Mr) and the coercive force (Hc) changed differently with increasing Co²⁺ Or Ni²⁺ content content.(3) Effects of microstructures and magnetic properties in various conditions have been investigated. The water volume, the amounts of citric acid, pH value, calcination temperature and time was determined to prepare pure fine well-dispersed nano-SrTiO₃ with citric acid method, and obtained the best synthesis conditions.(4) Ferroelectric/ferromagnetic multiphase nano-composite powders consisting of SrZn₂Fe₁₆O₂₇ as ferromagnetism and SrTiO₃ as ferroelectricity were firstly formed in situ by the citric acid method. The phase structure was measured by XRD and morphology was observed by TEM. The forming and growing processes are dependent on the calcinations temperature of the powder.