Infrared spectroscopy and luminescence spectra of Yb3+ doped ZrO2 nanophosphor

Unveiling the Effects of Rare-Earth Substitutions on the Structure, Mechanical, Optical, and Imaging Features of ZrO2 for Biomedical Applications

The impact of selective rare-earth (RE) additions in ZrO₂-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, Yb³⁺, Dy³⁺, Tb³⁺, Gd³⁺, Eu³⁺, and Nd³⁺ 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 ZrO₂. The significance of tetragonal ZrO₂ (t-ZrO₂) → monoclinic ZrO₂ degradation is evident with 10 mol % of RE substitution, while RE contents in the range of 20 and 40 mol % ensured either t-ZrO₂ or cubic ZrO₂ (c-ZrO₂) stability until 1500 °C. High RE content in the range of 80-100 mol % still confirmed the structural stability of c-ZrO₂ for lower-sized Yb³⁺, Dy³⁺, and Tb³⁺, while the c-ZrO₂ → RE₂Zr₂O₇ phase transition becomes evident for higher-sized Gd³⁺, Eu³⁺, and Nd³⁺. A steady decline in the mechanical properties alongside a quenching effect experienced in the emission phenomena is apparent for high RE concentrations in ZrO₂. On the one hand, the paramagnetic characteristics of Dy³⁺, Tb³⁺, Gd³⁺, and Nd³⁺ fetched excellent contrast features from magnetic resonance imaging analysis. On the other hand, Yb³⁺ and Dy³⁺ added systems exhibited good X-ray absorption coefficient values determined from computed tomography analysis.