DENSIFICATION BEHAVIOR OF Y3FE5O12 MATERIALS PREPARED BY MICROWAVE SINTERING PROCESS

The microwave sintering (ms) process is observed to be superior to a c onventional sintering (cs) process in the densification of Y3Fe5O12 ma terials. A density of 97.3% theoretical density (T.D.) with pure garne t phase and small grain size (5 similar to 7 mu m) was obtained for ma terials microwave sintered at 1300 degrees C for 20 minutes. By contra st only 94.3% of T.D. can be reached for materials sintered by convent ional processing at 1425 degrees C for 8h and the grains are large (si milar to 25 mu m). A higher densification rate in microwave sintering process, as compared to that in conventional sintering processing, is ascribed to the lower activation energy of densification (i.e., (E-a)( ms)=83.3 kcal/mol and (E-a)(cs)=163.2 kcal/mol). On the other hand, sm all grain size in microwave sintered samples is attributed to the fact that the (E-a)(ms)-value is smaller than the activation energy of gra in boundary migration (i.e., E-g=94.8 kcal/mol).