Temperature-dependent spectra of YPO4:Me (Me = Ce, Pr, Nd, Bi)

Temperature-dependent luminescence studies of Bi3+, Ce3+, Pr3+, and Nd3+ doped YPO4 are reported. The emission spectra of YPO4:Ln recorded under irradiation with vacuum ultraviolet light (160 nm) show emission bands in the UV due to transitions from the lowest crystal field component of the 4f(n-1)5d(1) configuration to the lowest terms of the 4f(n) ground state configuration. In addition to that, the emission spectra of YPO4:Pr and YPO4:Nd show also several emission lines in the UV and in the visible range due to transitions between electronic terms of the 42 and 4173 configuration. By increasing the temperature, the emission bands of YPO4:Ln broaden and their intensity decreases, a phenomenon which is well known as thermal quenching. Additionally, the intensity of certain emission lines of YPO4:Nd increases due to non-radiative relaxation from the 4f(n-1)5d(1) level to excited levels of the 4f(n) ground state configuration. This results in a shift of the intensity ratio of 4f(2)5d(1) --> 4f(3) emission bands to 4f(3) --> 4f(3) emission lines. In this paper, the thermal quenching parameters of YPO4:Ln and the dependence of the intensity ratio of 4f(2)5d(1) --> 4f(3) and 4f(3) --> 4f(3) emission for YPO4:Nd are derived and discussed in detail. (C) 2003 Elsevier B.V. All rights reserved.