Synthetic carboapatites doped with different metals for EPR dosimetry

In this work it was studied the influence that the structural parameters and the sorption of metallic ions exercise in the Electron Paramagnetic Resonance spectrum (EPR) of the paramagnetic species CO2- in B-type synthetic, trying to be considered the potential of this material in applications in the dosimetry. The spectrum of EPR was analyzed in X-band of samples of carboapatites of the Btype with different contents of carbonate, ration Ca/P and surface area, besides samples that suffered sorption experiments for the metals Li, Na, Fe, Co, Ni, Zn, Cd and Pb. The EPR spectra of these samples are constituted by the species CO2- with orthorhombic symmetry and of the species CO- and H-CO- with axial symmetry. It was verified that the structural parameters, ration Ca/P, carbonate content and surface area influence simultaneously about the formation of the radical CO2- in the B-type carboapatite. It was also verified that the presence of species CO- influence in the amount of radicals CO2- produced in the carboapatite by radiation. The samples that went by the experiment of surface sorption of different metals present similar EPR spectra to that of pure carboapatites. However the presence of the metal in the surface of the apatite alters the number of CO2- species created by irradiation in the material. The sorption of metals like Pb, Co, Li, Na, Zn and Ni increases the EPR signal of the species CO2- , while sorption of Fe and Cd decreases the EPR signal intensity. The presence of the metals in the surface of the carboapatite crystals doesn't alter signal fading. (author)