Strengthening of alumina by cerium-zirconate (Ce2Zr2O7)

Composite powders of Al2O3 and 0 to 30 vol% Ce2Zr2O7 are prepared by a hybr id sol-gel method using Al2O3 powders and a sol formed from Zr-alkoxide and cerium nitrate. All the Zr from the sol goes to form the cerium zirconate phase when the powders are calcined in N-2. Pressureless sintering in air a t 1500 degrees C yields composites with high density (similar to 98%). Maxi mum values of fracture toughness and strength, 6.5 MPa root m and 620 MPa r espectively, (e.g. 3.5 MPa root m and 350 MPa for pure Al2O3) are obtained in 10 vol% Ce2Zr2O7 composite sintered in air. The dominant mechanism for e nhancement in K-IC is believed to be crack bridging. Crack bridging activit y in the 10 vol% composite is found to be maximum and extends upto similar to 190 mu m from the crack tip. (C) 2000 Kluwer Academic Publishers.