The Effect of Full-Scale Exchange of Ca2+ with Co2+ Ions on the Crystal Structure and Phase Composition of CaHPO4•2H2O

The influence of ionic substitution in the Ca1-xCoxHPO4 & BULL;nH(2)O compound was studied systematically for the first time. Among the fascinating features of these biomaterials is that they can be easily tailored for specific applications, for example, as biocements and bioceramics. Different molar concentrations of Co(NO3)(2)& BULL;6H(2)O, Ca(NO3)(2)& BULL;4H(2)O, and NaH2PO4 & BULL;2H(2)O compounds were employed in determining the starting solutions utilized in the present study. The experimental findings reveal that, when the Co/Ca molar ratio is below 0.67 (BCo4), Co doping (the partial substitution of Ca by Co) takes place in brushite as a monophase. However, in the Co/Ca 0.67-1.5 molar ratio range (BCo4-BCo6), biphasic Co-3(PO4)(2)& BULL;8H(2)O/CaHPO4 & BULL;2H(2)O crystals start to precipitate. Full Ca replacement by Co results in the precipitation of nanostructured monoclinic cobalt phosphate and orthorhombic ammonium cobalt phosphate hydrate. Subsequent X-ray photoelectron spectroscopy (XPS), powdered X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) analyses, along with thermogravimetric analysis (TGA), confirmed that the starting solution ratio of Co/Ca had a significant influence on the material's microstructure, while tuning this ratio ultimately tailored the desired properties of the material for the intended applications.

Automated summary

The influence of ionic substitution in the Ca1-xCoxHPO4 & BULL;nH(2)O compound was systematically studied for the first time. The experimental findings revealed that the Co/Ca molar ratio had a significant impact on the material's microstructure, and tuning this ratio ultimately tailored the desired properties of the material for specific applications.