X-ray diffraction study of damage induced by swift heavy ion irradiation in fluorapatite

X-ray powder and high-resolution single-crystal diffraction techniques were used to study the irradiation damage of fluorapatites. Krypton, iodine and carbon irradiations were performed at high energy (≈1 MeV/a) in the 1011 to 5 × 1013 cm−2 fluence range. Both diffraction techniques showed a strong unit-cell increase of the fluorapatite structure, with a full relaxation of the remaining part of the material for large fluences. X-ray powder experiments revealed an amorphization of the material up to 85% for fluences around 1013 ions cm−2. Simulation of the relationship between amorphous volume fraction and fluence evidenced that the amorphization mechanisms could be dominated by a single impact process for iodine and double impacts for krypton. The effective radius of the track core remained nearly constant although the electronic energy loss increases from Kr to I. Moreover total amorphization of fluorapatite irradiated by swift heavy ions could not be obtained in this study. Experiments performed on (0 0 2)-oriented single-crystals allowed us to separate the change of the c-parameters of the damaged and virgin phases, and pointed out an anisotropic response of the material to the damage process.