Comparative study on the microstructure and mechanical behavior of monolithic ceramic and laminated composite of high strength 3Y-TZP and high fracture toughness 12Ce-TZP

Stabilized tetragonal zirconia is a biocompatible ceramic with high mechanical properties that is considered by different industries. In this research, the effect of fabrication of laminated composite with high strength 3 mol% yttria stabilized tetragonal zirconia polycrystal (3Y-TZP) ceramic as the outer layers (thickness of 1 mm for each layer) as well as high toughness 12 mol% ceria stabilized tetragonal zirconia polycrystal (12Ce-TZP) ceramic as inter layer (thickness of 1 mm) on the mechanical properties was investigated and the results were compared with monolithic samples. Nano-powders of 3Y-TZP and 12Ce-TZP obtained by the co-precipitation process were examined by X-ray diffraction (XRD) and field emission electron microscopy (FESEM). The powders were pressure-less sintered at 1450 °C after biaxial pressing at 60 MPa. The zirconia ceramics were polished and thermally etched and then observed under FESEM. The flexural strength, Vickers hardness and indentation fracture toughness of the samples were measured. The results show that the laminated structure yields a composite with the hardness of 1100 HV and a 41% increase in fracture toughness (10.57 MPa m^1/2) perpendicular to the layers relative to the fracture toughness of monolithic 3Y-TZP ceramic (7.5 MPa m^1/2). The use of laminated structure can change the fracture mode from brittle fracture in 3Y-TZP and 12Ce-TZP ceramics to a non-catastrophic fracture in the 3Y-TZP/12Ce-TZP laminated composite.