H. El Feki et al., Studies by thermally stimulated current (TSC) of hydroxy- and fluoro-carbonated apatites containing sodium ions, J PHYS-COND, 12(38), 2000, pp. 8331-8343
Carbonated hydroxyapatites (HAPCO(3)Na) and fluoroapatites (FAPCO(3)Na) con
taining sodium ions have been precipitated by the hydrothermal method.
The effect of carbonate and sodium substituted for phosphate and calcium re
spectively on the dipolar mobility of the OH- and F- ions located inside th
e apatitic channels of those samples has been studied by thermally stimulat
ed current (TSC). in both apatites two relaxation modes, around -100 and +5
0 degrees C, have been observed.
In the HAPCO(3)Na sample, the relaxation mode fine structure reveals the ex
istence of two cooperative phenomena with compensation temperatures in the
vicinity of the hydroxyapatite monoclinic-hexagonal transition. After prehe
ating of samples at 400 degrees C, the presence of cooperative movements is
confirmed by the observation of a compensation phenomenon with a compensat
ion temperature equal to 214 degrees C. An x-ray diffraction study is in ag
reement with this attribution.
As for the FAPCO(3)Na sample, the fine structure of the lower temperature r
elaxation mode only reveals a compensation phenomenon at 5 degrees C attrib
uted to water molecule reorientations inside apatitic channels.