Structural investigations of lead-strontium fluoroapatites

Solid solutions in the system Pb(10-x)Sr x (PO4)6F2, 0≤x≤10, were obtained as apatitic phases from aqueous medium. They were investigated by X-ray diffraction, chemical analysis and infrared (IR) spectroscopy. The results of the structural refinements indicated that the substitution of lead by strontium induces a regular decrease of the lattice constant 'a' and a preferential strontium distribution in site M(1). A progressive shift of the F- ion position along the apatitic channel was detected and confirmed by IR evidence. The different character of the M-F and M-O interactions was invoked to justify the structural differences observed as a function of composition. - Graphical abstract: The structural refinements carried out on five Pb(10-x)Sr x (PO4)6F2 samples evidence preferential distribution of cations in metal sites and a progressive shift of the F- ion