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.