Study On The Coating Process And Sintering Dynamics Of Mn-Zn Ferrite

The MnZn ferrite nanocrystal coating with citric acid, polyvinyl alcohol and sodium dihydrogen phosphate has been successfully synthesized by a simple synthesis, co-precipitation phase transformation. The compact sintered MnZn ferrite was gained by two-step sintering process. The physical and magnetic properties of the MnZn ferrite powder and sintered compacts were measured by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM), Nim2000 testing system of magnetic material and vibrating sample magnetometer (VSM), respectively. The mechanics of MnZn ferrite grain growth at sintering were analysed.The properties of Mn-Zn ferrite crystal show that: The optimal properties of Mn-Zn ferrite nanocrystal coating can be synthesized, with the citric acid doses 4.76%, polyvinyl alcohol doses 1% and sodium dihydrogen phosphate doses 0.01mol·L^-1, and the average grain size is about 26nm. The uniform grain and better magnetic property were prepared.According to the study on the MnZn ferrite powder coating with citric acid, the grain growth dynamics of powder was established. It shew the dynamics efficient n and the activation energy of reaction was estimated to be 3 and 45.33 KJ·mol^-1, respectively.To avoid the abnormal grain growth of sintering process, the two-step sintering was used. The temperature was rised to a higher temperature at first. Then it lowered to an exact temperature and remained for some time. As a result, the abnormal grain growth was not occurred in the sintering process. The combination property was optimum when the sintered temperature arrived 1000℃, its density was 4.7468 g·cm^-3.According to the relationships between sintered temperatures and grain size, and with the sintering equation of diffusion mechanism deduced by sphere model, the formula of grain growth dynamics was established, the grain growth exponent n and the activation energy of reaction was estimated to be 2 and 71.14 KJ·mol-1, respectively. It was shown that the grain growth was controlled by crystal boundary migration mechanism.