Rare-earth elements characterization in natural apatite: microprobe analyses and coupled SEM/CL spectroscopy
Résumé
Natural apatite can show complex chemical compositions shifting the general formula Ca5(PO4)3(F,Cl,OH) to different isomorphs. Substitution of the constituent ions Ca2+, PO4 3- and F- by, e.g., OH-, Na+, REE3+, Y3+, CO3 -, SiO4-,NaCO3- are common. Ca2+ is often substituted by REE3+ and charge compensation is done by intrinsic electron defects, depletion of the constituent ions or coupled substitution. Consequently, the complex analyses of REE incorporation in apatite could give information about the chemical and structural alteration of apatite. Many REE are well known as luminescence activators, even at few ppm content, and apatite can display various luminescent emissions. The purpose of this work is to to use the combination of: * CL-microscopy * Microprobe quantitative REE analyses, * CL-spectroscopy coupled with Scanning Electron Microscopy for mapping the relative REE distribution, and identification of the luminescence activators.