Tetragonal to Cubic Transformation of SiO2-Stabilized ZrO2 Polymorph through Dysprosium Substitutions.

Partially stabilized tetragonal zirconia (t-ZrO2) is of particular interest for hard tissue replacements. Aging-related failures of the ceramic associated with the gradual transformation from t-ZrO2 to m-ZrO2 (monoclinic zirconia) can lead to its premature removal from the implant site. In addition, monitoring the satisfactory performance of the implant throughout its lifespan without invasive techniques is a challenging task. The magnetic resonance imaging (MRI) contrast ability of dysprosium (Dy3+) is well-established. To this aim, varied levels of Dy3+ additions in the ZrO2-SiO2 binary oxide system were explored. The results indicate the effective role of Dy3+ in the formation of thermally and mechanically stable c-ZrO2 (cubic zirconia) phase at higher temperatures. The presence of SiO2 influenced the t-ZrO2 stabilization, whereas Dy3+ tends to occupy the ZrO2 lattice sites to induce c-ZrO2 transition. Magnetic and MRI tests displayed the commendable contrast ability of Dy3+ stabilized ZrO2-SiO2 binary systems. Nanoindentation results demonstrate a remarkable enhancement of the mechanical properties.

Investigation on the structural, mechanical and in vitro biocompatibility features of CaZr4 (PO4 )6 influenced by Zn2+ substitutions.

The present study explores the possibility of Zn2+ substituted calcium zirconium phosphate [CaZr4 (PO4 )6 ] as a potential replacement for the existing materials in load bearing orthopedic applications. Pure CaZr4 (PO4 )6 ) and wide range of Zn2+ substitutions in CaZr4 (PO4 )6 have been synthesized through citrate assisted sol-gel technique. The characterization results confirmed the extraordinary structural stability displayed by CaZr4 (PO4 )6 until 1,550°C. Further, the flexibility of CaZr4 (PO4 )6 lattice to accommodate 40 mol% of Zn2+ has been determined. The microstructures of CaZr4 (PO4 )6 and Zn2+ substituted CaZr4 (PO4 )6 demonstrated irregular sized grains and cracks alongside the negligence to obtain definite grain boundaries. This has been reflected in the moderate mechanical properties of the investigated specimen; nevertheless, Zn2+ substituted CaZr4 (PO4 )6 displayed enhanced mechanical stability. Further, in vitro tests signified the remarkable biocompatibility and alkaline phosphatase activity of Zn2+ substituted CaZr4 (PO4 )6 .