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Crystal structure of cobalt‐substituted calcium hydroxyapatite nanopowders prepared by hydrothermal processing
Author(s) -
Veselinović Ljiljana,
Karanović Ljiljana,
Stojanović Zoran,
Bračko Ines,
Marković Smilja,
Ignjatović Nenad,
Uskoković Dragan
Publication year - 2010
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889809051395
Subject(s) - crystallite , high resolution transmission electron microscopy , cobalt , materials science , rietveld refinement , crystallinity , crystallography , transmission electron microscopy , powder diffraction , analytical chemistry (journal) , inductively coupled plasma , mineralogy , crystal structure , nuclear chemistry , chemical engineering , chemistry , nanotechnology , metallurgy , composite material , chromatography , plasma , physics , quantum mechanics , engineering
A series of cobalt‐exchanged hydroxyapatite (CoHAp) powders with different Ca/Co ratios and nominal unit‐cell contents Ca 10− x Co x (PO 4 ) 6 (OH) 2 , x = 0, 0.5, 1.0, 1.5 and 2.0, were synthesized by hydrothermal treatment of a precipitate at 473 K for 8 h. Based on ICP (inductively coupled plasma) emission spectroscopy analysis, it was established that the maximum amount of cobalt incorporation saturated at ∼12 at.% under these conditions. The effects of cobalt content on the CoHAp powders were investigated using ICP emission spectroscopy, particle size analysis, transmission electron microscopy (TEM) and high‐resolution transmission electron microscopy (HRTEM) analyses as well as X‐ray powder diffraction (XRPD) including Rietveld analysis. According to XRPD, all the materials are single‐phase HAp and CoHAp of low crystallinity. Rietveld analysis shows that Co enrichment causes the c cell parameter to decrease at a faster rate than the a cell parameter. A microstructural analysis showed anisotropic X‐ray line broadening due to crystallite size reduction. In CoHAp there is significant crystal elongation in [001], and the average size decreases with increasing cobalt content. The crystallite morphology transforms from rod‐like for the pure HAp to lamellae at the highest degree of Co substitution. The results of Rietveld refinement (symmetry, size and morphology of the crystallites) were confirmed by TEM and HRTEM analysis.