Structural investigations of lead–strontium fluoroapatites

Solid solutions in the system Pb(10−x)Srx(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.