Publication Date:
2016-10-08
Description:
Carbonated calcium apatites doped with a monovalent cation (Li + , Na + , or K + ) or a divalent cation (Mg 2+ or Zn 2+ ) were prepared in aqueous solution and analysed by powder X-ray diffraction, inductively coupled plasma atomic emission spectroscopy and infrared spectroscopy. The hypothesis that the location of carbonate in the apatite structure, either in place of hydroxide ions in the c -axis channels (A-type substitution) or in place of phosphate (B-type substitution), is affected by the solution energetics of the cation (specifically its enthalpy of hydration) was strengthened by the observation of larger amounts of A-type carbonate in apatites containing the monovalent cations in aqueous solution. It is shown that cations with low negative enthalpies of hydration favour A-type substitution, whereas cations with higher negative hydration enthalpies, such as divalent cations (Mg 2+ , Zn 2+ ), favour B-type substitution.
Print ISSN:
0026-461X
Electronic ISSN:
1471-8022
Topics:
Geosciences
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