Spectroscopic studies and Rietveld refinement of strontium-britholites

Strontium-britholites whose chemical formula was Sr10−xLax(PO4)6−x(SiO4)xF2, where x=0, 1, 2, and 4 were prepared by solid state reaction. The structural refinement carried out using the Rietveld method indicated that La3+ ions were located into the two sites with a strong preference for metal (2) sites especially for low contents. A progressive shift of the F− position along the c-axis outside the centre of the triangle formed by metal (2)-atoms was observed with the increase of x. The infrared and Raman spectra exhibited the characteristic vibration modes of PO4 and SiO4 groups confirming the incorporation of this last group into the apatite structure. The 29Si MAS-NMR spectra exhibited one resonance peak confirming the data obtained by X-ray diffraction, indicating that P and Si were located in the same crystallographic site.