Structural, Mechanical, Imaging and in Vitro Evaluation of the Combined Effect of Gd 3+ and Dy 3+ in the ZrO 2 -SiO 2 Binary System.

Mechanical strength and biocompatibility are considered the main prerequisites for materials in total hip replacement or joint prosthesis. Noninvasive surgical procedures are necessary to monitor the performance of a medical device in vivo after implantation. To this aim, simultaneous Gd3+ and Dy3+ additions to the ZrO2 -SiO2 binary system were investigated. The results demonstrate the effective role of Gd3+ and Dy3+ to maintain the structural and mechanical stability of cubic zirconia ( c-ZrO2 ) up to 1400 °C, through their occupancy of ZrO2 lattice sites. A gradual tetragonal to cubic zirconia ( t-ZrO2 → c-ZrO2 ) phase transition is also observed that is dependent on the Gd3+ and Dy3+ content in the ZrO2 -SiO2 . The crystallization of either ZrSiO4 or SiO2 at elevated temperatures is delayed by the enhanced thermal energy consumed by the excess inclusion of Gd3+ and Dy3+ at c-ZrO2 lattice. The addition of Gd3+ and Dy3+ leads to an increase in the density, elastic modulus, hardness, and toughness above that of unmodified ZrO2 -SiO2 . The multimodal imaging contrast enhancement of the Gd3+ and Dy3+ combinations were revealed through magnetic resonance imaging and computed tomography contrast imaging tests. Biocompatibility of the Gd3+ and Dy3+ dual-doped ZrO2 -SiO2 systems was verified through in vitro biological studies.