Ferrite Materials, Scanning Electron Microscopy Analysis

Based on the scanning electron microscopy (SEM) and energy dispersive x-ray spectrometer (EDS) analysis techniques, using microstructure investigation and micro-area composition analysis, the doped MnZn ferrite core materials were studied, and the reason of surface cracking of Y-A1 garnet-type ferrite (YAlIG) was found out. The main researches were as follows.1. In order to obtain high-resolution SEM image, the effect of sample character on the image quality was investigated; and the working parameters of Jeol 6490LV SEM were optimized. The features of the secondary electron image and backscattered electron image were compared, and the applicable objects for them were respectively illustrated.2. In order to improve quantitative analysis accuracy of energy dispersive x-ray spectrometer (EDS), the effect of sample character on the composition result was detected, and the instrumental operating parameters were optimized, which was based on theoretical study and experimental research. In addition, how to prepare the samples and reasonably process the collected spectrum were discussed. The all above pave the way for making full use of SEM-EDS to characterize the microstructure of ferrite materials.3. The microstructures of doped MnZn ferrites were characterized by SEM-EDS analysis techniques. The cross-section morphology and micro-area composition were analyzed. Compared to zero-doped MnZn ferrite, the microstructures of doped MnZn ferrites are different, such as typical distribution of the dopants, the corresponding grain size and uniformity, the state of the grain boundary and pore distribution (shape, size and quantity), the impurity distribution, etc. The typical doped microstructures were studied and the mechanism of the dopant's effect on microstructure and electromagnetic property were discussed. The results above are of referential value to the following doped ferrites research and development.4. After the temperature surging test for the microstrip circulator, on the screen of microstrip line, the YAlIG ferrite show surface cracking phenomenon. In order to find out the cracking reason, the impact strength of the YAlIG substrates (before silver-sintered, after silver-sintered and after temperature surging) were tested and compared. The results showed that the impact strength declined sharply after silver-sintered, so the sintering process was determined to do a detailed study. The microstructure of cross-section of YAlIG was analyzed using SEM-EDS techniques, the results show that in the process of silver-sintered, silver penetrate in YAlIG ferrite, furthermore, the influence of silver diffusion was discussed. Ultimately the reason of surface cracking was found out,some suggestions were given out to improve the reliability of YAlIG microstrip circulator.