The Effect of Zirconia Addition on Physical and Mechanical Characteristics of Granulated Alumina-Based Composites

This work investigates the influence of zirconia nanoparticles stabilized by 3 mol% yttria content (5-20 wt.%) on the microstructure, physical, and mechanical performance of granulated alumina. Samples were prepared by uniaxial pressing followed by sintering temperatures ranging from 1500°C to 1650°C, with a 50°C interval, and a 2-hour soaking time. Results showed that zirconia retarded densification at lower temperatures, while enhancing it at higher temperatures through grain refinement and pore elimination. 20 wt.% ZTA composites achieved the highest relative density (approximately 97.5%) when sintered at 1600°C. Mechanical properties improved with the increase of zirconia addition up to 15 wt.%. Achieving flexural strength of 438 MPa, fracture toughness of 6.6 MPa·m1/2, and hardness of 1770 HV. Further increase led to deterioration in mechanical properties due to the formation of monoclinic zirconia, as zirconia coalesced and exhibited an inherently lower hardness compared to alumina. An optimum of ~15 wt.% zirconia provided the optimum strength, toughness, and hardness in granulated alumina composites, offering a cost-effective processing route for structural ceramics.