Microscopic, crystallographic and thermoluminescent study of hydroxyapatite (Hap) doped with europium chloride (EuCl₃)

Hydroxylapatite is a compound widely used in the medical field as a bone reinforcement material or as dental implants and inlays. Therefore, in this field of research there is a great deal of information on the characteristics and properties of hydroxyapatite; however, new routes and synthesis conditions continue to be tested, experimenting with different precursors, in such a way as to obtain a material with specific characteristics (particle size, porosity, elemental composition, crystallinity), so that its response as a bio material is more efficient, while at the same time expanding its field of application in other areas, for example in medical physics to sense ionizing radiation. In this thesis, a relatively cheap and economic methodology is presented to obtain hydroxyapatite from fish scales, to apply it as a thermoluminescent dosimeter to sense and quantify doses of gamma radiation (ionizing radiation). The fish scales were collected in the municipal market of Ixtlahuaca, State of Mexico. Subsequently, they were subjected to a washing process to eliminate contaminating particles, then they were subjected to a sintering process at different temperatures (500, 700 and 900°C); another synthesis was carried out under the same conditions, only adding EuCl₃ as a dopant, in concentrations of 0.1 and 0.5% by weight. The morphological, chemical-elementary and crystallographic characterization was carried out by scanning electron microscopy and X-ray diffraction, finding the formation of hydroxyapatite with a high degree of purity and particle size of a few hundred nanometers in diameter. Finally, the samples obtained were exposed to gamma radiation emitted by a Co-60 source, analyzing the thermoluminescent response induced by the radiation in the samples obtained. Was observed that pure hydroxyapatite presents a thermoluminescent response whose intensity increases with the radiation dose received, was also observed that as the sintering temperature increases, the intensity of the thermoluminescent response increases. Likewise, was found that EuCl₃ is capable of increasing the thermoluminescent intensity of hydroxyapatite, making the hydroxyapatite-EuCl₃ system a promising material to quantify ionizing radiation fields. The results obtained in this work show that it is possible to obtain hydroxyapatite with a high degree of purity and crystallinity with thermoluminescent properties, from fish scales, giving added value to this material that is considered waste. (author)