The ESR Spectrum Near G=2 of Carbonated Calciumapatites Synthesized at High Temperature

The ESR spectrum near g=2 of several carbonated calciumapatites synthesized at high temperatures, is studied as a function of incident microwave power. It is shown that the ESR signal observed is the composition of several powder spectrum contributions, arising from different paramagnetic centres. At low microwave power, the spectrum essentially reduces to be superposition of two very related spectra, probably to be ascribed to two CO33− radicals. The major component is assigned to CO33− at a phosphate site, while the other can be due either to a CO33− at a hydroxyl site or a surface CO33−.