Bulk Yttria as a Host for Lanthanides in Biomedical Applications: Influence of Concentration Gradients on Structural, Mechanical, Optical, and Imaging Behavior.

The biomedical application of yttria (YO) as a bulk material to host a series of rare earth elements (RE) has been explored in the current investigation. Dy, Gd, Tb, Yb, Eu, and Nd were chosen for this purpose, and their corresponding concentrations in YO have been varied to obtain five different combinations. The results ascertain the potential of YO to host different RE to retain a discrete cubic yttria (-YO) devoid of significant structural distortion until 1400 °C. Depending upon the size of RE, either a contracted or expanded cubic YO unit cell has been determined from the XRD and Raman analyses. Other than the typical vibrational modes of -YO, Raman spectra also unveiled characteristic emission features of RE that were dependent on the excitation laser used to record the spectra. The characteristic absorption and emission characteristics depending on the type of RE substitutions were determined from the optical measurements. Pore free microstructures determined from the morphological analysis are reflected in the enhanced mechanical behavior of RE doped YO specimens. Dy and Yb substituted YO unveiled computed tomography (CT) imaging features. Dy, Tb, and Nd dopant compositions delivered magnetic resonance imaging (MRI) contrast features, while the specimen comprising Gd revealed both and MRI characteristics.