Fast 5d-4f luminescence of Pr3+ in new wide band-gap host lattices for applications in medical diagnostics

The work presented in this thesis is focused on the development and improvement of new wide band-gap luminescent materials used as fast scintillators in modern medical diagnostic techniques. The goal of this research consists in obtaining inorganic scintillators activated with trivalent preaseodymium (Pr3+) ion where a very fast interconfigurational d-f emission could be observed. The performance of scintillator materials is determined by the dissipation of high energy photons in a sequence of processes ultimately leading to the emission of visible or UV radiation. The understanding of the processes responsible for relaxation and migration of electronic excitations, and the transfer of energy to defects and impurity centers is crucial for successful development of new optical materials with enhanced performance, especially in terms of quantum efficiency, temporal response, radiation resistance, thermal and chemical stability. In the present work polycrystalline powders of Ca9LuPO4:Ce3+/Pr3+, K3Lu(PO4)2:Pr3+, KLuP2O7:Pr3+, X2SiO5:Pr3+ (X= Y, Lu) and single crystals of BaMgF4:Nd3+ were synthesized and characterized. A systematic study of time-resolved luminescence spectra and luminescence decay profiles of these materials was performed at the HASYLAB, DESY synchrotron facility in Hamburg (Germany) in order to understand the electronic structure of luminescent centers, the influence of defects, and the main mechanisms responsible for host-to-impurity energy transfer and relaxation of the host electronic excitation. The research proposed in this project will allow developing an adequate model of creation and relaxation of electronic excitations establishing the main principles for the synthesis of new materials with controllable optical and luminescence properties.