Densification behavior of Y3Fe5O12 materials prepared by microwave sintering process

The microwave sintering (ms) process is observed to be superior to a conventional sintering (cs) process in the densification of Y3Fe5O12 materials. A density of 97.3% theoretical density (T.D.) with pure garnet phase and small grain size (5 similar to 7 mu m) was obtained for materials microwave sintered at 1300 degrees C for 20 minutes. By contrast only 94.3% of T.D. can be reached for materials sintered by conventional processing at 1425 degrees C for 8h and the grains are large (similar 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, small grain size in microwave sintered samples is attributed to the fact that the (E-a)(ms)-value is smaller than the activation energy of grain boundary migration (i.e., E-g=94.8 kcal/mol).