Two new rare-earth orthoborates Ba2CdLn2(BO3)4 (Ln = Tb, Eu) and multicolor tunable emission in the Ba2CdTb2-2xEu2x(BO3)4 (0 ≤ x ≤ 0.2) phosphors

Abstract Two new rare-earth orthoborates Ba2CdLn2(BO3)4 (Ln = Tb, Eu) were prepared by the high-temperature solution reactions at 950 °C. The single-crystal XRD analyses showed that they crystallized in the monoclinic space group P21/c and the crystal structures consisted of 3D networks constructed by CdO5 square pyramids (CdO6 mono-capped square pyramids), Tb(Eu)On (n = 7, 8) polyhedra and BO3 planar triangles, with open channels accommodating Ba2+ cations. The IR and Raman studies supported the presence of BO3 groups in the structures and the UV–vis absorption measurements showed the typical Tb3+ and Eu3+ absorption bands arising from their unpaired 4f electrons. In addition, solid solutions Ba2CdTb2-2xEu2x(BO3)4 (0 ≤ x ≤ 0.2) were prepared via the solid-state reaction method. By doping Eu3+ into the Ba2CdTb2(BO3)4 host and varying the doping concentration of Eu3+, tunable colors from green to orange and eventually to red were obtained in the Ba2CdTb2-2xEu2x(BO3)4 phosphors under the excitation at 377 nm. The energy transfer process from Tb3+ to Eu3+ was verified through luminescence spectra and fluorescence decay curves. The above results indicated that the Ba2CdTb2-2xEu2x(BO3)4 phosphors may find potential applications in the field of displays and lighting.