Structure refinements by the Rietveld method of partially substituted hydroxyapatite: Ca9Na0.5(PO4)(4.5)(CO3)(1.5)(OH)(2)

Citation
H. El Feki et al., Structure refinements by the Rietveld method of partially substituted hydroxyapatite: Ca9Na0.5(PO4)(4.5)(CO3)(1.5)(OH)(2), J ALLOY COM, 287(1-2), 1999, pp. 114-120
Citations number
48
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
JOURNAL OF ALLOYS AND COMPOUNDS
ISSN journal
09258388 → ACNP
Volume
287
Issue
1-2
Year of publication
1999
Pages
114 - 120
Database
ISI
SICI code
0925-8388(19990601)287:1-2<114:SRBTRM>2.0.ZU;2-9
Abstract
The structural location and effect due to partially substitution of Na+ and CO32- to Ca+ + and PO43-, respectively, in hydroxyapatite, Ca-10(PO4)(6)OH 2 (HAP), synthesised in aqueous solution have been investigated by X-ray po wder pattern fitting methods. The compound crystallises in the hexagonal sy stem (space group P63/m) with the following cell: a = b = 9.3892(4) Angstro m, c = 6.9019(3) Angstrom. Using the Rietveld method, the refinement of occ upancy factors shows that the sodium is located preferentially in the calci um site II of the apatite structure. Vacancies in both calcium sites are fo und and the OH site is fully occupied. No carbonate ion is found in the apa tite channel, leading to a B type carbonate apatite. The carbonate ions are located an two faces of the PO4 tetrahedron. An extra shift of the OH- ion outside of the metal II triangle is attributed to the replacement of calci um by sodium and a vacancy. The corresponding new substitution mechanism is compared to already known fundamental mechanisms. (C) 1999 Elsevier Scienc e S.A. All rights reserved.