Defect Monitoring and Substitutions in Sr3-xAxAlO4F (A = Ca, Ba) Oxyfluoride Host Lattices and Phosphors

We show that a family of anion ordered oxyfluorides with the general composition Sr(3-x)A(x)MO(4)F with A = Ca, Ba and 0 <= x <= 1 and M = Ga1-zAlz and 0 <= z <= 1, which are promising new host lattices for near-UV excited phosphors with potential use in light-emitting devices, develop defect structures during exposure to reducing gases. These defects in anion-deficient nonstoichiometric (Sr(3-x)A(x))(1-alpha-2 delta)MO4-alpha F1-delta, can be monitored by broad-band photoluminescence emissions centered near 500 nm when excited with 254 nm UV light. We show how the broad-band photoluminescence emissions of these materials respond to synthesis parameters such as temperature, time, and reducing gas flow rate and argue that they could be used to monitor the long-term stability of these phosphors under UV light. Substituting indium into the oxyfluoride lattices we discovered a class of single phase materials with the general formula (Sr3-xBax)(1-alpha-2 delta)Al1-cIncO4-alpha F1-delta = 0-0.6, c = 0-0.2, and alpha, delta = 0-0.05) which show self-activating luminescence with an emission maximum near 600 nm when excited in the near-UV region near 400 nm.