Unveiling the Effects of Rare-Earth Substitutions on the Structure, Mechanical, Optical, and Imaging Features of ZrO for Biomedical Applications.

The impact of selective rare-earth (RE) additions in ZrO-based ceramics on the resultant crystal structure, mechanical, morphological, optical, magnetic, and imaging contrast features for potential applications in biomedicine is explored. Six different RE, namely, Yb, Dy, Tb, Gd, Eu, and Nd alongside their variations in the dopant concentrations were selected to accomplish a wide range of combinations. The experimental observations affirmed the roles of size and dopant concentration in determining the crystalline phase behavior of ZrO. The significance of tetragonal ZrO (-ZrO) → monoclinic ZrO degradation is evident with 10 mol % of RE substitution, while RE contents in the range of 20 and 40 mol % ensured either -ZrO or cubic ZrO (-ZrO) stability until 1500 °C. High RE content in the range of 80-100 mol % still confirmed the structural stability of -ZrO for lower-sized Yb, Dy, and Tb, while the -ZrO → REZrO phase transition becomes evident for higher-sized Gd, Eu, and Nd. A steady decline in the mechanical properties alongside a quenching effect experienced in the emission phenomena is apparent for high RE concentrations in ZrO. On the one hand, the paramagnetic characteristics of Dy, Tb, Gd, and Nd fetched excellent contrast features from magnetic resonance imaging analysis. On the other hand, Yb and Dy added systems exhibited good X-ray absorption coefficient values determined from computed tomography analysis.