Structural distortions in Sr3-xAxMO4F (A=Ca, Ba; M=Al, Ga, In) anti-Perovskites and corresponding changes in photoluminescence

The ordered oxyfluoride family Sr3−xAxMO4F (A=Ca, Ba and M=Al, Ga) has formed the basis of several new inorganic phosphors, and shows great potential for use in phosphor-conversion LED lamp devices. This study examines the correlation between subtle structural changes and photoluminescent behaviour in some of these materials. In order to ascertain whether cation charge compensation has any influence on structure and subsequent photoluminescent behaviour, a comparison was carried out between phases with the nominal compositions Sr2.975Ce0.025AlO4F and Sr2.95Ce0.025Na0.025AlO4F using structural characterisation based upon high-resolution neutron powder diffraction (NPD) data. Additionally, NPD data has been used to elucidate the role of different M cations in these materials, using Sr2.25Ba0.6Eu0.1M0.95In0.05O4−αF1−δ (M=Al, Ga) to determine the effect M cation size has on structure and photoluminescent properties.