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Tesi etd-04142023-141444


Tipo di tesi
Tesi di dottorato di ricerca
Autore
SIQUEIRA NASCIMENTO, DEBORA
URN
etd-04142023-141444
Titolo
Optimization of MgB4O7: Ce Li AS a Universal Dosimeter
Settore scientifico disciplinare
ING-IND/20
Corso di studi
INGEGNERIA INDUSTRIALE
Relatori
tutor Prof. d'Errico, Francesco
relatore Prof. Ciolini, Riccardo
relatore Prof.ssa De Sousa Lalic, Susana
Parole chiave
  • dosimetry
  • thermolumincence
  • magnesium tetraborate
Data inizio appello
19/04/2023
Consultabilità
Non consultabile
Data di rilascio
19/04/2026
Riassunto
MgB4O7 doped with rare earth ions (RE) has shown great potential for use in both personnel and clinical dosimetry applications. The material's effective atomic number, Zeff, is close to that of soft tissue, making it an ideal candidate for personal dosimetric assessments without the need for correction factors. Additionally, MgB4O7:RE is sensitive to various types of ionizing radiation such as electrons, photons, and beta particles. The material can also be enriched with B-10 and B-11 for thermal neutron detection, making it a strong candidate for universal dosimetry.
This work focused on optimizing the production processes of MgB4O7:RE and understanding the defects that play a significant role in luminescent mechanisms through computational simulation. To achieve this, samples of MgB4O7: Ce x%wt Li x%wt were produced using solid-state synthesis and analyzed using X-Ray Diffraction. The analysis confirmed that the majority of the phase production was successful.
The TL sensitivity of the pellets production was analyzed through sintering temperatures, granulometry, doping valence, percentage of doping, and light exposure. The results indicated that the optimal production was achieved with MgB4O7:0.5%+4Ce, 0.5%Li sintering at 825°C/1h. However, the production of pellets with a binder agglutination method was not recommended due to limitations during the reading processes.
The optimized material was then applied in various fields, including 60Co, 226Ra, 137Cs, X-Rays of low energy, and high energy radiotherapy fields. The results were promising, indicating that MgB4O7:RE could be a suitable candidate for use in dosimetry applications.
In addition to the experimental work, computational simulation was also carried out to understand the defects that play a significant role in the luminescent mechanisms of MgB4O7:RE. The simulation provided a new set of interatomic potential parameters that reproduced the MgB4O7 structure better than 2% and 4% regarding the ICSD for oxide precursors. The simulation results indicated that the most probable Frenkel defect could account for the intrinsic blue emission in the undoped material.
Further, the extrinsic defects calculations showed two possible doping schemes for lanthanides ions. One group of lanthanide dopants prefers substitution at the boron site, while the other group prefers substitution at the magnesium site. These findings provide valuable insights into the luminescent mechanisms of MgB4O7:RE and could be useful in optimizing its dosimetry applications.
In conclusion, MgB4O7 doped with rare earth ions is a promising material for use in personnel and clinical dosimetry applications. The experimental work focused on optimizing the production processes and testing the material's performance in various fields. The computational simulation work provided valuable insights into the defects that play a significant role in the luminescent mechanisms of MgB4O7:RE. These findings could be useful in optimizing the dosimetry applications of MgB4O7:RE and improving its performance in various radiation fields.
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