Abstract
Two alkali-earth and rare-earth metal borates, M3Eu2(BO3)4 (M = Ba, Sr), have been synthesized and their crystal structures determined by single-crystal XRD methods with the following crystal data: Ba3Eu2(BO3)4 (1), Pnma, a = 7.6970(15) Å, b = 16.554(3) Å, c = 8.9300(18) Å, V = 1137.8(4) Å3, Z = 4; Sr3Eu2(BO3)4 (2), Pnma, a = 22.2553(4) Å, b = 15.9122(3) Å, c = 8.7568(2) Å, V = 3101.05(11) Å3, Z = 12. The compound 1 is isotypic with Ba3RE2(BO3)4 (RE = Y, La, Pr, Nd) and its crystal structure features a 3D framework constructed by BO3 triangles and 8-fold coordinated positions M1, M2 and M3 with mixed Eu/Ba occupation. 2 adopts a threefold superstructure of the structure of 1. IR and Raman spectra further confirm that both 1 and 2 contain the planar triangular BO3 groups. The photoluminescence spectra of 1 and 2 consist of five groups of emission bands assigned to the 5D0→7Fj (j = 0, 1, 2, 3, 4) transitions within Eu3+ ions and the decay curves show the single-exponential behavior with the lifetime being 1.358 and 0.887 ms for 1 and 2, respectively. 1 possess a very high luminescent efficiency (QE = 90.09%) which benefited to being applied in warm white LEDs. Moreover, X-ray photoelectron spectroscopy (XPS) is used to analyze the chemical states of the elements and the band electronic structure on 1 has also been investigated.
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