Structural Perceptions and Mechanical Evaluation of β-Ca(PO)/c-CeO Composites with Preferential Occupancy of Ce and Ce.

The role of cerium in the formation of stable β-Ca(PO)/c-CeO composites and their structural analysis with varied compositional ratios were investigated. The composite formation was attempted through an in situ precipitation technique, and the gradual structural changes during heat treatments to yield the pure form of β-Ca(PO)/c-CeO composites was presented. The cerium was found in Ce and Ce oxidation states in composites. Ce prefers to occupy the Ca(1), Ca(2), and Ca(3) sites of β-Ca(PO), whereas, beyond the saturation occupancy limit, excess cerium prefers to crystallize in the form of thermodynamically stable cubic ceria (c-CeO). A uniform expansion of the β-Ca(PO) unit cell and the delayed allotropic conversion of β-Ca(PO) → α-Ca(PO) have been detected due to the Ce occupancy at the β-Ca(PO) lattice. β-Ca(PO)/c-CeO composites exhibited a steady upsurge in the mechanical properties with consistent enhancement of c-CeO content in the composites. The overall results from the investigation imply the appropriateness of the β-Ca(PO)/c-CeO composites for applications in hard tissue replacements.