Increased fluorescence intensity in CaTiO3:Pr3+ phosphor due to NH3 treatment and Nb Co-doping

Abstract Development of next generation red phosphors for commercial lighting requires understanding of how increased luminescence is achieved by various treatment strategies. In this work, we compare co-doping with Nb to NH 3 treatment of CaTiO 3 :Pr phosphors to reveal a general mechanism responsible for the increased luminescence. The phosphors were synthesized using standard solid-state synthesis techniques and the fluorescence was characterized for potential use in fluorescent lighting, with 254 nm excitation. The lifetime of the fluorescence was determined and used to identify a change in a trap state by the co-doping of Nb 5+ in the phosphor. The oxidation state of the Pr was probed by NEXAFS and revealed that both Nb 5+ co-doping and NH 3 treatment reduced the number of non-fluorescing Pr 4+ centers. Calculations were performed to determine the energetically favorable defects. Vacuum annealing was also used to further probe the nature of the trap state. It was determined that NH 3 treatments reduce the number of Pr 4+ non-fluorescing centers, while Nb 5+ co-doping additionally reduces the number of excess oxygen trap states that quench the fluorescence.