Influence of Yttrium Oxide Distribution on Microstructure and Properties of Zirconia Based on Alternative Doping Routes

The sensitivity of the stress-induced tetragonal to monoclinic (t → m) phase transformation in zirconia ceramics is significantly affected by the addition of rare-earth dopants, which subsequently influences its mechanical properties. However, how to achieve zirconia with varying rare-earth ion distributions and investigate their properties is difficult. Based on the co-precipitation, coating, and ball milling methods, this work successfully achieved a uniform distribution of rare-earth ions and systematically studied the effect of yttrium oxide distribution on the microstructure and mechanical properties of zirconia. The t → m transformation sensitivity during the fracture was assessed through X-ray diffraction, scanning electron microscopy, and Raman spectroscopy, and the results show that both the fracture toughness and flexural strength of zirconia are positively correlated with the increase in sintering temperature. The coated zirconia demonstrated superior fracture strength, and the co-precipitated zirconia exhibited enhanced flexural strength. The enhanced mechanical properties of the coated zirconia are attributed to the non-uniform distribution and un-aggregation of rare-earth dopants within the matrix. Additionally, the high stress-induced phase transformation rate (~ 33.3%) and the significant transformation depth (~ 35 μm) in rare-earth-deficient regions contribute to the material's improved toughness.