Structures and self-activating photoluminescent properties of Sr3−xAxGaO4F (A=Ba, Ca) materials

The synthesis, structures and photoluminescent properties of mixed oxyfluorides of the type Sr3−xAxGaO4F are compared to Sr3−xAxAlO4F (A=Ca, Ba) materials. In these compounds the F− and O2− ions are ordered and located on two distinct crystallographic sites. When substituting Sr2+ by Ba2+ and Ca2+, we find in Sr3−xAxGaO4F materials an ordering of the alkaline earth cations over the two crystallographic sites. The amount of Ba2+ ions that can be substituted into Sr3−xAxGaO4F is x≤1.2, which is slightly more than can be incorporated into the previously reported Al-analog Sr3−xAxAlO4F (x=1.0). Conversely, the amount of Ca2+ ions that can be substituted into Sr3−xCaxGaO4F (x=0.3) is significantly less than in Sr3−xCaxAlO4F (x=1.0). A post-synthesis reduction step causes these materials to exhibit self-activating broad band photoluminescence where the emitted colors vary with the amount of ions substituted into the host lattice.

Graphical abstractTOC Statement The structures of the self-activating phosphors Sr3−xAxMO4F (A=Ba, Ca and M=Al, Ga) can be rationalized as alternating layers of bond compression and elongation, which impact the photoluminescence.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Comparison of the structural changes in Sr3−xAxAlO4F and Sr3−xAxGaO4F (A=Ba, Ca) and its influence on the photoluminescence of these self-activating phosphors. ► Analysis of the Global Instability Index of the Sr3−xAxAlO4F and Sr3−xAxGaO4F (A=Ba, Ca). ► Comparison of the photoluminescence between the self-activating phosphors Sr3−xAxAlO4F and Sr3−xAxGaO4F (A=Ba, Ca).