Influence of the Pr concentration in NaLaF4

Abstract

Understanding of luminescence processes and the discovery of novel phosphors is of increasing importance. With the possibility of replacing mercury gas in fluorescent tubes novel phosphors are necessary with increased efficiency. In this thesis the luminescence and quantum cutting of NaLaF4:Pr3+ is investigated. NaLaF4:Pr3+ samples with varying concentrations of Pr3+ were studied. Luminescence decay curves and emission spectra were recorded and analyzed of room temperature and cooled samples. The resulting lifetimes were used to discover the influence of the different non-radiative decay processes and the influence of temperature and concentration on those processes. The main processes of non-radiative decay are energy migration and cross-relaxation. It was concluded that at low concentrations NaLaF¬4:Pr3+ is an efficient quantum cutter. At higher concentrations the influence of concentration quenching lowers the efficiency significantly. It was also concluded that the influence of temperature was insignificant for low concentration samples. For high concentration samples the influence was bigger but not enough to reach the wanted efficiencies. Overall it was concluded that NaLaF4:Pr3+ is an good quantum cutting material at concentrations of at most 10%.