Phase transition, radio- and photoluminescence of K3Lu(PO4)2 doped with Pr3+ ions

Luminescent characteristics of K3Lu(PO4)(2):Pr3+ (1 and 5 mol.%) microcrystalline powders, a promising optical material for scintillation applications, were investigated using various experimental techniques. The material shows emission features connected with both high intensity interconfigurational 4f(1)5d -> 4f(2) transitions (broad UV emission bands) and intraconfigurational 4f(2)-> 4f(2) transitions (weak emission lines in the visible range). The output of X-ray excited 4f(1)5d -> 4f(2) emission of Pr3+ increases with a temperature rise from 90 K to room temperature and higher depending on the Pr3+ ions concentration. The high 5% concentration of Pr3+ ions is found to be favourable for the stabilization of a monoclinic phase (P2(1)/m space group) over a trigonal one (P (3) over bar space group) while emission properties of the material reveal that a phase transition occurs at higher temperatures. Decay kinetics of Pr3+ 4f(1)5d -> 4f(2) emission are recorded upon excitation with high repetition rate X-ray synchrotron excitation and pulse cathode ray excitation. Issues related to a non-exponential decay of luminescence and presence of slow decay components are discussed in terms of energy transfer dynamics. The presence of defects was revealed with thermoluminescence measurements and these are suggested to be the mainly responsible for delayed recombination of charge carriers on the Pr3+ 4f(1)5d states. Some peculiarities of host-to-impurity energy transfer are discussed.