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.

A series of Dysprosium (Dy3+) doped β‐Tricalcium phosphate [β‐TCP, β‐Ca3(PO4)2] were developed for applications in magnetic resonance imaging (MRI) and computed tomography (CT). Characterization studies confirmed the Dy3+ occupancy at Ca2+(1), Ca2+(2), and Ca2+(3) lattice sites of β‐Ca3(PO4)2 and its substitution limit was determined as 4.35 mol%. The transitions from the 6H15/2 ground state to various excited energy levels is validated by the characteristic absorption peaks of Dy3+. Luminescence studies inferred two intense bands at 480 and 572 nm due to 4F9/2→6H15/2 (blue) and 4F9/2→6H13/2 (yellow) transitions of Dy3+. The paramagnetic and nontoxic behavior of Dy3+‐doped β‐Ca3(PO4)2 were confirmed from magnetic and MTT tests, respectively. Dy3+ in the host induces a high X‐ray absorption ability for X‐ray computed tomography (CT) and showed efficient contrast T2‐enhancing modality. Thus the proposed system could be used as a promising probe for multimodality with optical imaging, computed tomography and magnetic resonance imaging.

To compensate the limitations of bone tissue magnetic resonance imaging (MRI), a series of gadolinium (Gd ) substituted β-Tricalcium phosphate [β-TCP, β-Ca (PO ) ] were developed. All the powders were characterized using XRD, Raman spectroscopy, Rietveld refinement of the XRD data and the studies confirmed the Gd occupancy at Ca (1), Ca (2) and Ca (3) lattice sites of β-Ca (PO ) HR-TEM analysis revealed the spherical nature of particles with diameter about 100 nm. The Gd doped β-Ca (PO ) exhibited non-toxic behaviour to MG-63 cells in vitro and the room temperature magnetic field versus magnetization measurements confirmed its paramagnetic behaviour. MRI analysis revelas that it shorten both T and T proton relaxation times, thus influencing both r and r relaxivity values that reach 61.97 mM s and 73.35 mM s . © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2545-2552, 2017.

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