THE RELATIONSHIP BETWEEN CRYSTALLINE STRUCTURE, MICROSTRUCTURE AND THE MECHANICAL PROPERTIES OF ALUMINA ZIRCONIA COMPOSITE CERAMICS

This research studied the relationship between crystalline structure, microstructure and the mechanical properties of composite ceramics between Al2O3 and ZrO2 with 60:40 ratio. Al2O3 was doped MgO 6.0 mol% to form AM and ZrO2 was doped Y2O3, 4.0 mol% to form ZY. Composite ceramics was prepared under two-step sintering method with five different sintering temperature conditions. The x-ray diffraction patterns revealed a phase compositions between Al2O3 and ZrO2. Rietveld method was used to identify the quantitative phase analysis and obtained a high ratio of t-ZrO2, c-ZrO2 phases from the two stage sintering condition with T1 temperature at 1650°C for 60 min and T2 temperature at 1550°C for 5 h, and T1 temperature at 1650°C for 60 min and T2 temperature at 1500°C for 10 h. The bulk densities values tended to slightly increase with the lower T2 temperature for the length of holding times. SEM micrographs revealed grain shape and size of grains. The grains were spherical in shape combined with irregular shape. The average grain size of AM as 0.951-1.205 µm and ZY was 0.739-0.894 µm:, the average grain size tended to increase with high T2 temperature for the length of holding time. EDX identified large grains corresponding to the Al2O3 phase and small round oval shapes corresponding with the ZrO2 phase. Good mechanical properties are found in the samples with sintering conditions temperatures of T1 temperature at 1650°C for 60 min and T2 temperature at 1550°C for 5 h; this resulted were given the highest of fracture toughness value of about 0.38 GPa.m1/2. The optimal two stage sintering conditions were obtained from a high ratio of t-ZrO2 and c-ZrO2 phases with high bulk densities.