A new rare-earth borate Sr3Dy2(BO3)4 and tunable luminescence properties of Sr3Dy2-2xEu2x(BO3)4 phosphors

A new rare-earth borate Sr3Dy2(BO3)(4) was obtained by high-temperature solution reaction at 950 degrees C and structurally characterized by single-crystal XRD for the first time. It crystallizes in the orthorhombic system (Pnma group, Z = 12) with cell parameters of a = 22.2265(3) & Aring;, b = 15.8861(2) & Aring;, c = 8.7096(1) & Aring;, V = 3075.29(7) & Aring;(3). The compound features a complex 3D framework constructed by (Dy/Sr)O-n (n = 7, 8, and 9) polyhedra and BO3 planar triangles. Moreover, solid solutions of Sr3Dy2-2xEu2x(BO3)(4) (0 <= x <= 0.2) were prepared via the solid-state reaction route. The obtained products were characterized by powder XRD/Rietveld refinement, SEM/EDS, IR/Raman, XPS, DRS, and photoluminescence techniques. It was found that all samples were in the yellow-white light region under excitation at 351 nm. Among them, Sr3Dy1.6Eu0.4(BO3)(4) exhibits the CIE coordinates of (0.3292, 0.3536), close to the standard white-light illumination. When lambda(ex) = 394 nm, as the Eu3+ content varies from x = 0 to 0.2, the emission color of Sr3Dy2-2xEu2x(BO3)(4) can be adjusted from yellow-white (0.3280, 0.3834) to yellow-pink (0.5373, 0.3667). Thus, color-tunable and white emissions can be achieved by controlling the wavelength of the excitation light and the Eu3+/Dy3+ ratio. Meanwhile, the temperature-dependent analysis of Sr3Dy1.6Eu0.4(BO3)(4) proved the high thermal stability, with the emission intensity at 150 degrees C remaining >75 % of its value at room temperature. These results indicate that Sr3Dy2-2xEu2x(BO3)(4) has the potential as a single-phase white-emitting phosphor for w-LED applications.