Changes in the Sr3AlO4F and Ba2SrGaO4F structures were studied using high resolution neutron diffraction annealing these materials in 5%H2/95%Ar and 4%H2/96% Ar, respectively. Annealing in these atmospheres causes self-activated photoluminescence (PL) to occur under 254nm light, which makes them ideal materials for rare-earth free compact fluorescence lamp (CFL) phosphors. Additionally, these host possess two distinct sites for isovalent or aliovalent substitution of Sr denoted as the A(1) and A(2) sites. Ga3+ can be substituted for Al3+ at the M site which his known to have an impact the self-activated PL emission color. The structural distortions noted included closer packing in the FSr6octahedrons and AlO4 tetrahedrons in the Sr3AlO4F structure as compared to in air-annealed samples which shows no PL emission. Temperature-dependent studies reveal that both the air- and reductively-annealed samples have identical thermal expansion within this temperature range (3K-350K). High-resolution neutron diffraction at room temperature confirmed the tetragonal structure (I4/mcm) for Ba2SrGaO4F, a novel material in the Sr3AlO4F family of materials, has been synthesized via solid-state method. Analysis of the refined Ba2SrGaO4F structure at room temperature revealed expansion in the lattice parameters and its polyhedral sub-units between the reductively annealed and air-annealed samples, which are correlated with the PL emission. Previous studies related to the application of these host structure types revealed that they have potential as commercial solid-state lighting phosphors due to its ability to resist thermal quenching as well as accommodating various levels of substitutions that will assist with color tunability.

Structural and photoluminescence characterization of oxyfluorides for phosphor applications

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