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Abstract: Cadmium substituted strontium hydroxy- and fluoro-apatites, Sr(10−x)Cd x (PO4)6Y2 (Y=OH and F), have been prepared as single phases in the 0≤ x ≤4 interval for the former and 0≤ x ≤6 for the latter compound, respectively. The refinements of the X-ray full powder patterns allowed the structure determination of nine samples, and showed a preference of cadmium atoms for the M(1) site in fluoroapatite samples. IR investigation gave information about the nature of the metal oxygen interactions. The obtained results are used for a comparative discussion about the factors which drive the mutual substitution of Ca, Sr, Cd and Pb in apatites. The important role of electronegativity and polarisability, as well as of ionic radii, is evidenced. [Copyright &y& Elsevier]

Copper-substituted calcium in hydroxyapatite nanocrystals (CuHAp) were synthesized by co-precipitation method and characterized using various analyses. Structural and chemical characterizations indicate that copper was quantitatively incorporated into the HAp structure, replacing calcium up to 15 at.%. The presence of copper in the HAp structure affected clearly its crystallinity and reduced its crystallite sizes. Rietveld analysis showed a regular decrease of the CuHAp cell parameters a and c. Moreover, this substitution caused a shift in the infrared absorption bands and the nuclear magnetic resonance signals of phosphate groups and a decrease in the thermal stability. Morphological characterizations indicated that the prepared CuHAp consists of extremely thin needle-shaped nanocrystals with a greater aggregation, and confirmed the decrease in crystal size that was associated to the increasing in the surface area. The prepared CuHAp nanocrystals showed a high catalytic effect (up to 70%) in the discoloration of the Naphthol Blue Black solutions. [ABSTRACT FROM AUTHOR]