Study On Microwave Sintering Of Strontium Ferrite Permanent Magnetic Materials

Strontium ferrites have enjoyed an increasing extensive application in production and living areas for its strength of the higher performance to price ratio, the high Curie temperature and the better chemical stability. Hence, the development and utilization of strontium ferrite industry has become one of the most important developing directions of Magnetic Material Industry. There are two aspects to be explored in the improvement of the magnetic properties: on the one hand, the magnetic properties and physical property of materials can be improved by the mingling of microelements and the further substation of various ions; on the other hand, the magnetic properties of the permanent magnet materials can be enhanced by improving the ferrite production process, among which the key process lies in the sinter technology. This experiment replaces the traditional sintering technology with microwave sintering method to produce strontium ferrites, in order to optimize the microstructure and magnetic properties of magnets and develop a new technique that combines the low-consuming production and the controllable sinter. The following lists the main conclusions:The results reveal that the material microstructure could be improved by microwave sintering (MS) method. The grain size significantly reduced. The degree of orientation and the apparent density increased. The strontium ferrite samples with the same magnetic properties (Br and (BH)max were 420±10mT and 33.0±2 kJ/m3) were synthesized by microwave sintering (MS) method. According to the traditional sintering method, the sintering temperature and time were reduced 150~300℃and 5~6h. So microwave sintering method significantly decrease energy consumption. The magnetic properties of strontium ferrite reach the Japanese TDK FB6 standard by microwave sintering. And in microwave sintering process, to select the sufficient oxygen atmosphere and the appropriate holding time was conducive to the increase of the magnetic properties.The pole figure analysis was introduced to characterize the degree of orientation of grains. The results shows that the (008) pole figures of the samples have a maximum for polarized intensities atα=0°except the sample at MS 950℃. It can be seen that the polarized intensity shows a maximum atα≈30°only in the (107) pole figure of the sample at MS 1000℃. This phenomenon described the optimum technical condition is the process of MS 1000℃, which was corresponds to the magnetic properties and the degree of orientation.The study on preparation of strontium ferrite magnetic tiles by microwave sintering process was introduced. The results showed that the strontium ferrite magnetic tiles can be successfully prepared by microwave sintering process, and even can be prepared at 950℃. Compared with conventional sintering in factory, when the temperature of MS technique could reach above 1000℃, the magnetic properties and strength of the samples by CS can be received. The magnetic properties and strength of the tiles were the maximum points at 1050℃.