Polymorphs and derivates of Sr2LiAlO4:Eu2+

Recently, Wang et al. (Z. Wang, J. Ha, Y. H. Kim, W. B. Im, J. McKittrick, S. P. Ong, Joule 2018, 2, 914 -926) predicted and discovered Sr2LiAlO4, a quaternary compound with a layered structure crystallizing in the monoclinic space group P2(1)/m, and they refined the structure from PXRD data. Upon partially substituting strontium with europium, the substance exhibits a yellow broadband luminescence consisting of two overlapping emission bands. In this paper, the crystal structure of Sr2LiAlO4 is confirmed by additional SC-XRD measurements and a newly discovered polymorph of Sr2LiAlO4, is presented crystallizing in the orthorhombic space group Cmcm. When Et2+ is incorporated, this polymorph exhibits only one of the emission bands present in the P2(1)/m-polymorph. Additionally, two substitutional variants of Sr2LiAlO4 are presented along with their luminescence properties upon incorporating Eu2+. One with a partial substitution of strontium for barium, leading to a structure in space group Pnma, and one with a partial substitution of oxygen for nitrogen, exhibiting the structure in space group Cmcm. The structure-property relationships in the above mentioned compounds are discussed with regard to their luminescence performance.