Novel “Anti-Zeolite” Ba3Sr3B4O12: Eu3+ Phosphors: Crystal Structure, Optical Properties, and Photoluminescence

Novel Ba3Sr3B4O12: Eu3+ phosphors were synthesized by crystallization from a melt. The crystal structures of Ba3(Sr3−1.5xEux)B4O12 (x = 0.03, 0.06, 0.15, 0.20, 0.25) solid solutions were refined from SCXRD data. The crystal structures of Ba3(Sr3−1.5xEux)B4O12 phosphors can be described in terms of the cationic sublattice and belong to the “anti-zeolite” family of borates. Its cationic framework is constructed of Ba and Sr atoms. The Eu3+ ions occupy the Sr(1) extraframework cationic site in the Ba3(Sr3−1.5xEux)B4O12 (x = 0.01–0.20) phosphors. The Ba3Sr2.625Eu0.25B4O12 borate crystallizes in a new structure type (I4/mcm, a = 13.132(3), c = 14.633(4) Å, V = 2523.5(11) Å3, Z = 8, R1 = 0.067). In the Ba3Sr2.625Eu0.25B4O12 crystal structure, the Eu3+ ions occupy Sr(1) and Ba/Sr(1) sites, which leads to changes in the crystal structure. The Wyckoff letter and occupancy of the O(5) site are changed; B–O anion groups contain two BO3 triangles (B(3) and B(4)), orientationally disordered over the four orientations, and two ordered BO3 triangles (B(1) and B(2)) in contrast to Ba3Sr3B4O12, in which these groups are disordered over the 4 and 8 orientations. The emission spectra of Ba3Sr3B4O12: Eu3+ show characteristic lines corresponding to the intraconfigurational 4f-4f transitions of Eu3+ ions. Ba3Sr2.7Eu0.20B4O12 demonstrates the strongest luminescent intensity among Ba3(Sr3−1.5xEux)B4O12 solid solutions. The increase in the Eu3+ content results in a gradual change in chromaticity from light red to orange-red/red. It can be concluded that Ba3Sr3B4O12: Eu3+ is a promising red phosphor.