Luminescence Quenching of [M]NbO4:Pr3+ [M=La, Lu, Gd] Under UV Excitation

We report on the luminescence properties of three Pr³⁺-doped niobate systems (LaNbO4, LuNbO₄, and LaNbO₄) in the temperature range between 7K and 500K. These systems are d⁰ oxides that exhibit a metal-to-metal charge transfer state lying just below the conduction band. Pumping in the UV, the system exhibits the typical sharp line emission from the ³P₀ and ¹D₂ levels of Pr³⁺. The emission intensities from these levels are temperature and host dependent, with the ¹D₂ emission showing strong quenching at higher temperatures. In addition to the Pr emission, we also observe broad-band emission from the niobate complex. Using results from steady state luminescence and kinetic studies, we discuss the flow of energy in these systems following uv excitation, and also consider the quenching mechanism of the luminescence from these systems.