Densification and grain growth in BaTiO3 ceramics fabricated from nanopowders synthesized by ball-milling assisted hydrothermal reaction

BaTiO3 powders synthesized by hydrothermal reaction assisted with or without ball milling were used to fabricate sintered bulk BaTiO3 ceramics. The sintering rate of BaTiO3 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 BaTiO3 powders synthesized without ball milling, the relative density and the shrinkage of sintered compacts were measured to be 60% and 5% at 900 °C and 94.3% and 13% at 1000 °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% and 8% at 900 °C and 98.6% and 24% at 1000 °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 × 105 and 8.4 × 105 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.