Densification behaviour of Y3Fe5O12 materials prepared by microwave sintering process

The microwave sintering (ms) process is observed to be superior to conventional sintering (cs) in the densification of Y₃Fe₅O₁₂ materials. A density of 97.3% theoretical density (T.D.) with pure garnet phase and small grain size (5~7 μm) was obtained for materials microwave sintered at 1300°C for 20 minutes. By contrast, only 94.3% of T.D. can be reached for materials sintered by conventional processing at 1425°C for 8 h and the grains are large (~25 μm). A higher densification rate in the microwave sintering process, as compared with 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 (E_g=94.8 kcal/mol)