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

Abstract

The impact of selective rare-earth (RE) additions in ZrO 2 -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 3+ , Dy 3+ , Tb 3+ , Gd 3+ , Eu 3+ , and Nd 3+ 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 2 . The significance of tetragonal ZrO 2 (t-ZrO 2 ) → monoclinic ZrO 2 degradation is evident with 10 mol % of RE substitution, while RE contents in the range of 20 and 40 mol % ensured either t-ZrO 2 or cubic ZrO 2 (c-ZrO 2 ) stability until 1500 °C. High RE content in the range of 80−100 mol % still confirmed the structural stability of c-ZrO 2 for lower-sized Yb 3+ , Dy 3+ , and Tb 3+ , while the c-ZrO 2 → RE 2 Zr 2 O 7 phase transition becomes evident for higher-sized Gd 3+ , Eu 3+ , and Nd 3+ . A steady decline in the mechanical properties alongside a quenching effect experienced in the emission phenomena is apparent for high RE concentrations in ZrO 2 . On the one hand, the paramagnetic characteristics of Dy 3+ , Tb 3+ , Gd 3+ , and Nd 3+ fetched excellent contrast features from magnetic resonance imaging analysis. On the other hand, Yb 3+ and Dy 3+ added systems exhibited good Xray absorption coefficient values determined from computed tomography analysis.

Simultaneous accommodation of Dy3+ at the lattice site of β‐Ca3(PO4)2 and t‐ZrO2 mixtures: Structural stability, mechanical, optical, and magnetic features

“…Further, a gradual surge in the magnetic response with simultaneous increment in the Dy 3+ addition ensures the fact that magnetic response is triggered only by the influence of Dy 3+ . The results from the optical and magnetic measurements deliberated good consistency in terms of emission bands, concentration‐dependent quenching effect, and paramagnetic features of either Dy 3+ ‐doped β ‐Ca 3 (PO 4 ) 2 or Dy 3+ ‐doped ZrO 2 structures …”

“…The RE 3+ incorporation is mainly due to the attractive optical and magnetic features displayed by these elements in biomedicine . RE 3+ substitution in ZrO 2 has been an extensive study that enumerates the positive impact in the resultant structure such as to accommodate a wide range of either individual or multiple RE 3+ substitutions devoid of significant structural distortion . It has been deduced that depending on the concentration of RE 3+ substitution in increasing order, a gradual phase transition in the order of tetragonal ( t ‐ZrO 2 ) to cubic ZrO 2 ( c ‐ZrO 2 ) and thereafter the formation of pyrochlore structure are witnessed .…”

Combined Occupancy of Gadolinium at the Lattice Sites of β‐Ca3(PO4)2 and t‐ZrO2 Crystal Structures

“…In particular, the stabilization capacity of Y 3+ (1.019 Å) in ZrO 2 has been documented extensively in previous reports that ensured the stabilization of tetragonal ZrO 2 polymorph with Y 3+ content in the range of 3–8 mol‐%, while its cubic polymorph is retained beyond 8 mol‐% , . In a similar manner, the effects of rare earth elements on the stabilization capacity of ZrO 2 polymorphs have been documented , , . 10 mol‐% of individual substitution of different rare earths such as Yb 3+ (0.985 Å), Dy 3+ (1.027 Å), Tb 3+ (1.040 Å), Gd 3+ (1.053 Å), Eu 3+ (1.066 Å) and Nd 3+ (1.109 Å) ensured t ‐ZrO 2 stabilization until 1500 °C.…”

“…In addition, the substitution of Gd 3+ also fetch MRI features that enhance the propensity of β‐Ca 3 (PO 4 ) 2 to be employed as a bone substitute alongside an imaging tool. In a similar manner, Gd 3+ has also been used as a viable stabilizer to retain either tetragonal or cubic polymorph of ZrO 2 depending on its dopant concentration , . The gradual addition of Gd 3+ prefers to occupy along a = b ‐axis of tetragonal ZrO 2 [ t ‐ZrO 2 ] to induce a steady expansion of the resultant axis until a particular limit and thereafter transforms to cubic ZrO 2 [ c ‐ZrO 2 ] polymorph .…”

“…In a similar manner, Gd 3+ has also been used as a viable stabilizer to retain either tetragonal or cubic polymorph of ZrO 2 depending on its dopant concentration. [9,19] The gradual addition of Gd 3+ prefers to occupy along a = b-axis of tetragonal ZrO 2 [t-ZrO 2 ] to induce a steady expansion of the resultant axis until a particular limit and thereafter transforms to cubic ZrO 2 [c-ZrO 2 ] polymorph. [20][21][22] It is a wellknown fact that t-→ m-ZrO 2 [monoclinic ZrO 2 ] phase transition has been considered a major shortcoming of the ZrO 2 implants in orthopaedic applications.…”