Correlation among composition, microstructure and mechanical properties of ZrO_2 (Y_2O_3)/Al_2O_3 composite ceramics

摘要

The aim of this work is to correlate the microstructure of alumina toughened zirconia (ATZ) and zirconia toughened alumina (ZTA) composites with the Vickers hardness, flexural strength and fracture toughness. The monoclinic zirconia (m-ZrO_2) phase has completely been transformed into tetragonal zirconia (t-ZrO_2) phase for Al_2O_3 content. The presence of 3 mol% yttria-stabilised zirconia (3YSZ) particles on the grain boundaries effectively limits a rapid grain growth of the Al_2O_3 grains. The average grain sizes of pure Al_2O_3 and 3YSZ as well as Al_2O_3 and t-ZrO_2 in the 3YSZ + 40 wt% Al_2O_3 composite were 3.78 μm, 1.82 μm, 0.89 μm and 0.83 μm, respectively. The 3YSZ + 40 wt% Al_2O_3 composite showed maximum flexural strength of 395 MPa, fracture toughness of 5.6 MPa.m~(1/2) and intermediate Vickers hardness of 15.01 GPa with the highly dense microstructure consisting of higher t-ZrO_2 grains of the critical size, which make it suitable for dental applications.