Densification and grain growth in BaTiO_3 ceramics fabricated from nanopowders synthesized by ball-milling assisted hydrothermal reaction

摘要

BaTiO_3 powders synthesized by hydrothermal reaction assisted with or without ball milling were used to fabricate sintered bulk BaTiO_3 ceramics. The sintering rate of BaTiO_3 green compacts produced by ball-milling assisted hydrothermal reaction was found to be faster than that prepared by hydrothermal reaction without ball milling. In the case of green compacts produced by BaTiO_3 powders synthesized without ball milling, the relative density and the shrinkage of sintered compacts were measured to be 60 percent and 5 percent at 900 deg C and 94.3 percent and 13 percent at 1000 deg C, respectively. On the other hand, the relative density and the shrinkage of sintered compacts produced by ball-milling assisted hydrothermal reaction were measured to be 96.5 percent and 8 percent at 900 deg C and 98.6 percent and 24 percent at 1000 deg C, respectively. Furthermore, the free energy for grain-growth activation was estimated from the relationship between grain size and sintering temperature. The free energy for grain-growth activation of the sample produced by the hydrothermal reaction assisted with or without ball milling was calculated to be 4.2 X 10~5 and 8.4 X 10~5 J/mol, respectively. It was found that the grain-growth of green compacts produced by assistance of ball milling was promoted at lower-sintering temperature.