The influence of firing temperatures on the phase formation, microstructure and mechanical properties of alumina zirconia composite ceramics

Abstract

This research prepared composite ceramics between Al2O3 (6 mol% MgO); AM and ZrO2 (4 mol% Y2O3); ZY with 50:50ratio. The samples were sintered under two-step method with four different sintering temperature conditions. It was foundthat the densities and shrinkage values tended to slightly increase with the lower T2 temperature for the length of holdingtimes. XRD patterns showed a combination main phase between Al2O3 and ZrO2. Rietveld refinement was used to calculatethe percentage of phase composition. All of samples were reveled weight percentage of main composition as m-ZrO2 c-ZrO2t-ZrO2 and r-Al2O3 in different sintering conditions. Rietveld analysis of data revealed a high ratio of t-ZrO2, c-ZrO2 phasesfrom the two stage sintering condition with T1 temperature at 1600 °C for 60 min and T2 temperature at 1450 °C for 10 h, andT1 temperature at 1600 °C for 60 min and T2 temperature at 1500 °C for 5 h. SEM micrographs revealed grain shape and sizeof grains. The average grain size of AM as 0.863-1.156 μm and ZY was 0.622-0.902 μm:, the size of grain tended to increasewith high T2 temperature for the length of holding time. EDX identified large grains corresponding to the Al2O3 phase andsmall round oval shapes corresponding with the ZrO2 phase. The mechanical properties were measured by Vicker and Knoophardness calculate the fracture toughness value. It was found that the optimum mechanical properties were obtained fromcomposite ceramic with sintering conditions temperatures of T1 temperature at 1600 °C for 60 min and T2 temperature at 1450°C for 10 h; this resulted in the highest of fracture toughness value of about 0.32 GPa∙m1/2. The optimal two stage sinteringconditions were obtained from a high ratio of t-ZrO2 and c-ZrO2 phases with fine grain size.