La ions in precipitated hydroxyapatites.
Hydroxyapatites were synthesized by precipitation from an aqueous solution with La3+ (0-0.75%) and with carbonate (0-6.1%) at controlled pH 7.0. Uptake of La3+ was 90-95% complete. Relatively low Ca/P (1.54-1.63) ratios were attributed to nonstoichiometry. Carbonate in samples was identified by IR spectroscopy as B-type carbonate. Lattice parameters of the hexagonal apatite structure were not affected by the La3+ content. Noncarbonated samples heated to 800 degrees C transform partially to beta-Ca3(PO4)2. Thermogravimetric analysis showed release of 0.4 mol adsorbed and 1 mol crystalline water up to 400 degrees C and decomposition of carbonate up to 900 degrees C in the samples. Luminescence data obtained for Gd-containing hydroxyapatites prove that Gd3+ ions are not incorporated in the precipitated hydroxyapatite. These findings suggest that, in the La-containing samples, La3+ is surface absorbed and not incorporated in hydroxyapatite.
Mayer
I
I
Department of Inorganic and Analytical Chemistry, Hebrew University, Jerusalem, Israel. isaacm@vms.huji.ac.il
Layani
J D
JD
Givan
A
A
Gaft
M
M
Blanc
P
P
D002118:Calcium / Q000032:analysis; D011232:Chemical Precipitation; D006882:Hydroxyapatites / Q000737:chemistry*; D007811:Lanthanum / Q000032:analysis*; D008163:Luminescent Measurements; D013055:Spectrophotometry, Infrared; D013696:Temperature
D006882:Hydroxyapatites; D007811:Lanthanum; D002118:Calcium