Synthesis and thermal behavior of Mg-doped calcium phosphate nanopowders via the sol gel method

The aim of this study was to investigate the thermal behavior of Mg-doped calcium phosphate compounds. Nanocrystalline HA and ββ-TCP mixtures containing different magnesium contents were synthesized via an alkoxide sol gel method. The ratio of (Ca+Mg)/P was kept constant at 1.67, and the Mg content ranged between 0 and 3 mol%. The influence of magnesium on the phase composition, chemical structure, thermal behavior and morphological characteristics of nanopowders was analyzed using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Simultaneous Thermogravimetry and Differential Thermal Analysis (STA/DTA), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Based on the results of this research, the presence of magnesium led to the formation of Mg-doped hydroxyapatite (Mg-HA) and Mg-doped tricalcium phosphate (ββ-TCMP) phases. The characteristic peaks of apatite structures have been identified in the FTIR spectra. It was found that both the presence of magnesium and low Ca/P ratio caused the formation of a biphasic mixture, even at 470 °C. In addition, the ββ-TCP to αα-TCP transformation temperature increased due to the presence of magnesium ions. Morphological investigations showed that the synthesized powders were composed of nanoparticles, with sizes ranging from 40 to 100 nm.