Elaboration and Characterization of Phosphosilicates Apatites Containing Lanthanum

Two series of strontium–lanthanum apatites, Sr10-xLax(PO4)6-x(SiO4)xF2 and Sr10-xLax(PO4)6-x(SiO4)xO with 0 x 6, were synthesized by solid state reaction in the temperature range of 1200–1400°C. The obtained materials were characterized by X-ray diffraction, NMR spectroscopy and infrared and Raman measurements were performed to investigate the crystal structure and vibrational active modes. Pure solid solutions were obtained within a limited range of unsubstituted phosphate and silicate apatites. A variation of the lattice parameters was observed, with an increase of a and a decrease of c parameters, related to the radius of the corresponding substituted ions. The bands of Infrared and Raman spectra were assigned to the vibration modes of PO4 and SiO4 groups. The comparison of the results of 29Si MAS NMR analysis with those obtained with the 31P, suggested that both species occupied the same crystallographic sites.