Chemical segregation in a 12Ce-ZrO2/3Y-ZrO2 ceramic composite

Abstract

In restorative dentistry, 3Y-ZrO2 ceramics are widely accepted for fabricating dental crowns, bridges and implants due to their good biocompatibility, excellent mechanical properties and high aesthetics potential. However, they suffer from low temperature degradation (LTD) in the presence of water species, which generates a loss in their surface mechanical integrity. If ceria is used instead of yttria, as in 12Ce-ZrO2, both higher fracture toughness and resistance to LTD are achieved. The composition of solutes inside the grains and at the grain boundaries is essential for understanding their role in LTD. In the present work, a microstructural study by means of wavelength-dispersive spectroscopy, transmission electron microscopy and atom probe tomography has been conducted by investigating the distribution of elements such as Ce, Y, Al and Zr in the solid solution of zirconia that results from mixing 85wt% 12Ce-ZrO2 and 15wt% 3Y-ZrO2 and sintering at two different temperatures, 1450 and 1600°C. It is shown that the solid solution inside the grains after sintering at any of the two temperatures is not homogenous, being closer to the expected equilibrium concentration when sintering at 1600°C. Segregation of Ce, Y and Al to the grain boundaries is also analysed by atom probe tomography showing that the segregations are stronger in the specimens sintered at the higher temperature.