ESR study of 13C-enriched carbonated calciumapatites precipitated from aqueous solutions.
The ESR spectrum of X-irradiated carbonated apatites precipitated from aqueous solutions was studied at carbonate contents ranging from approximately 5.4 up to 12.4 wt%. 12C- as well as 13C-enriched samples were prepared and examined with ESR after dying until constant weight at 25 degrees C and 400 degrees C. In these carbonated apatites, two CO3(3-) radicals were detected, one of which is derived from B-type carbonate situated at a phosphate lattice site. The other CO3(3-) most probably arises from CO3(2-) ions situated at OH- lattice sites. In contradistinction to the B-type contribution, the A-type contribution to the overall ESR signal decreases in absolute terms with increasing carbonate concentration. In addition, the line shape and the complete set of principal g-values of the A1-signal found in previous studies could be determined, corroborating the assignment of A1 to a surface O- ion.
Laboratory for Crystallography and Study of the Solid State, University Gent, Belgium.
F J
FJ
Callens
R M
RM
Verbeeck
D E
DE
Naessens
P F
PF
Matthys
E R
ER
Boesman
D001031:Apatites / Q000737:chemistry*; D002254:Carbonates / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D012996:Solutions; D014961:X-Ray Diffraction
D001031:Apatites; D002254:Carbonates; D012996:Solutions