Synthesis of bone implant substitutes using organic additive based zirconia nanoparticles and their biodegradation study

Zirconia, a hard-ceramic, is potential material for bone and dental implants. However, the problem limiting its application is inertness. This problem can be minimized using body compatible and non-toxic organic additives. Organic additives-based zirconia (OZ) nanoparticles are synthesized using sol-gel method. Zirconium oxychloride is used as precursor and water as solvent. OZ nanoparticles are calcined in the temperature range of 100-1000 °C. Transition from mixed zirconia phases to amorphous behavior is observed at 300 °C. Phase-pure tetragonal ZrO₂ (t-ZrO₂) along with reduced crystallite size ~12.7 nm is observed at 500 °C. Mixed phases, appearing at 800 °C, exhibit increased monoclinic to tetragonal ratio at 900-1000 °C. SEM images show OZ nanoparticles with ~50 nm diameter at 500 °C. Nanoparticles with ~50 nm and ~70-75 nm diameter along with nanowires (~8 nm) are observed at 600-700 °C. FTIR band at 500 cm^-1 along with shoulder at 580 cm^-1 and Raman band at 148 cm^-1 confirm the presence of t-ZrO₂ at 500-600 °C. High value of hardness, ~15 GPa, and dielectric constant (~57 68) suitable for bio-application is observed for OZ nanoparticles calcined at 500 °C. Optimized t-ZrO₂ is immersed in stimulated body fluid for 1, 2, 4, 8, 13, 20 and 26 weeks. Small degradation in weight and hardness is observed even after 26 weeks of immersion.