Novel “Anti-Zeolite” Ba[sub.3]Sr[sub.3]B[sub.4]O[sub.12]: Eu[sup.3+] Phosphors: Crystal Structure, Optical Properties, and Photoluminescence

Novel Ba[sub.3]Sr[sub.3]B[sub.4]O[sub.12]: Eu[sup.3+] phosphors were synthesized by crystallization from a melt. The crystal structures of Ba[sub.3](Sr[sub.3−1.5x]Eux)B[sub.4]O[sub.12] (x = 0.03, 0.06, 0.15, 0.20, 0.25) solid solutions were refined from SCXRD data. The crystal structures of Ba[sub.3](Sr[sub.3−1.5x]Eux)B[sub.4]O[sub.12] 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 Eu[sup.3+] ions occupy the Sr(1) extraframework cationic site in the Ba[sub.3](Sr[sub.3−1.5x]Eux)B[sub.4]O[sub.12] (x = 0.01–0.20) phosphors. The Ba[sub.3]Sr[sub.2.625]Eu[sub.0.25]B[sub.4]O[sub.12] borate crystallizes in a new structure type (I4/mcm, a = 13.132(3), c = 14.633(4) Å, V = 2523.5(11) Å[sup.3], Z = 8, R[sub.1] = 0.067). In the Ba[sub.3]Sr[sub.2.625]Eu[sub.0.25]B[sub.4]O[sub.12] crystal structure, the Eu[sup.3+] 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 BO[sub.3] triangles (B(3) and B(4)), orientationally disordered over the four orientations, and two ordered BO[sub.3] triangles (B(1) and B(2)) in contrast to Ba[sub.3]Sr[sub.3]B[sub.4]O[sub.12], in which these groups are disordered over the 4 and 8 orientations. The emission spectra of Ba[sub.3]Sr[sub.3]B[sub.4]O[sub.12]: Eu[sup.3+] show characteristic lines corresponding to the intraconfigurational 4f-4f transitions of Eu[sup.3+] ions. Ba[sub.3]Sr[sub.2.7]Eu[sub.0.20]B[sub.4]O[sub.12] demonstrates the strongest luminescent intensity among Ba[sub.3](Sr[sub.3−1.5x]Eux)B[sub.4]O[sub.12] solid solutions. The increase in the Eu[sup.3+] content results in a gradual change in chromaticity from light red to orange-red/red. It can be concluded that Ba[sub.3]Sr[sub.3]B[sub.4]O[sub.12]: Eu[sup.3+] is a promising red phosphor.