Fabrication and characterization of sol–gel derived hydroxyapatite/zirconia composite nanopowders with various yttria contents

Homogeneous composite nanopowders of hydroxyapatite/30 wt% yttria-stabilized zirconia (HA–YSZ) containing 0, 3, 5, and 8 mol% Y2O3 (namely; HA–0YSZ, HA–3YSZ, HA–5YSZ, and HA–8YSZ) were successfully synthesized using the sol–gel method. Simultaneous thermal analysis (STA), X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), Fourier transformed infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques were utilized to characterize the prepared nanopowders. Analyses of HA–YSZ composite nanopowders showed the successful formation of desirable phases. HA unit cell volume in the composites increased as a result of ion exchange of calcium and zirconium between HA and zirconia. Results revealed the formation of HA particles with irregular morphology (40–80 nm) and spherical yttria-stabilized zirconia particles (20–30 nm). Segregation of yttrium ions at the grain boundaries of ZrO2 particles retarded the grain growth of zirconia particles and the presence of ZrO2 nanoparticles among the hydroxyapatite particles resulted in grain growth inhibition of HA particles. This process can be used to synthesize HA–YSZ composite nanopowders with improved properties, which are much needed for hard tissue repair and biomedical applications.