CONVENTIONAL AND MICROWAVE SINTERING STUDIES OF SRTIO3

Using the nonconventional sintering technique, such as microwave sinte ring, it is observed to enhance the densification rate of SrTiO3 mater ials as effectively as employing the highly active powders prepared by the chemical route. Although the chemically derived powders demonstra te better sinterability than the mixed oxide powders, the thermal anal ysis indicates that the segregation of Ti4+-containing clusters during decomposition of precursors in the direct pyrolysis (DP) process indu ces the occurrence of TiO2 particles (anatase phase) prior to the form ation of SrTiO3 phase. These particles retard the necking process requ ired to sinter the materials. The spray pyrolysis (SP) process can cir cumvent the preferential nucleation of TiO2 phase and, therefore, prod uce powders exhibiting superior sintering behavior to the DP-derived p owders. The microwave sintering technique, on the other hand, substant ially enhances the rate of-diffusion of the ions in the materials such that even the mixed oxide powders can be sintered at a temperature ab out 200 degrees C lower than that needed to achieve the same density i n a conventional sintering process. Fine grain (similar to 4 mu m) mic rostructure is obtained for the materials microwave sintered at 1220 d egrees C for 10 min. The migration of grain boundaries requires higher temperature to initiate than the formation of neckings between the gr ains. The grain growth occurs only when the material was sintend at te mperatures higher than 1250 degrees C.