Microstructure of sol-gel synthesized Al2O3-ZrO2(Y2O3) nano-composites studied by transmission electron microscopy

Abstract

The Al2O3–ZrO2(Y2O3) composite powder was synthesized through a sol–gel process using aluminum sec-butoxide and zirconium butoxide as precursors. The as-received powders in an amorphous phase were crystallized with c-ZrO2 at around 980 °C. As the calcination temperature increased, the c-ZrO2 crystalline phase was transformed to t-ZrO2 at about 1200 °C. However, the Al2O3 phase in the Al2O3–ZrO2(Y2O3) composite powders still existed in an amorphous phase up to 1050 °C. In the sintered body using the calcined powders at 400 °C, the Al2O3 phase was crystallized in an α-phase at 1200 °C during the sintering for 2 h. Using the sol–gel Al2O3–ZrO2(Y2O3) powder, a typical nano-composite having a nano-crystalline phase (less than 20 nm) can be successfully obtained by a pressureless-sintering process even at 1200 °C for 2 h. Using the sol–gel Al2O3–ZrO2(Y2O3) powder, a typical nano-composite having a nano-crystalline phase (less than 20 nm) can be successfully obtained by a pressureless-sintering process even at 1200 °C for 2 h. The values of relative density and Vickers hardness were comparatively high value with about 96.2% and 1100 Hv, respectively, even though it was made at low temperature. In the composite sintered at 1400 °C, the hardness value was saturated with 1570 Hv and the values of fracture toughness were almost same with about 6 MPa m1/2.