A new caesium sodium samarium borate phosphate, CsNa2Sm2(BO3)(PO4)2, has been obtained successfully by the high-temperature solution growth (HTSG) method and single-crystal X-ray diffraction analysis reveals that it crystallizes in the orthorhombic space group Cmcm. The structure contains BO3, PO4, NaO7 and SmO7 polyhedra which are interconnected via corner- or edge-sharing O atoms to form a three-dimensional [Na2Sm2(BO3)(PO4)2]∞ network. This network delimits large cavities where large Cs+ cations reside to form the total structure. Under 402 nm light excitation, CsNa2Sm2(BO3)(PO4)2 exhibits three emission bands due to the 4f→4f transitions of Sm3+. Furthermore, we introduced Gd3+ into Sm3+ sites to optimize the Sm3+ concentration and improve the luminescence intensity. The optimal concentration is Gd/Sm = 98/2. The luminescent lifetime of a series of CsNa2Gd2(1–x)Sm2x (BO3)(PO4)2 phosphors shows a gradual degradation of lifetime from 2.196 to 0.872 ms for x = 0.01–0.10. The Commission Internationale de l'Eclairage (CIE) 1931 calculation reveals that CsNa2Gd1.96Sm0.04(BO3)(PO4)2 can emit orange light under 402 nm excitation.
Langbeinite-type compounds are a large family that include phosphates, sulfates and arsenates, and which are accompanied by interesting physical properties. This work reports a new disordered langbeinite-type compound, K2GdHf(PO4)3 [dipotassium gadolinium hafnium tris(phosphate)], and its structure as determined by single-crystal X-ray diffraction. Theoretical studies reveal that K2GdHf(PO4)3 is an insulator with a direct band gap of 4.600 eV and that the optical transition originates from the O-2p→Hf-5d transition. A Ce3+-doped phosphor, K2Gd0.99Ce0.01Hf(PO4)3, was prepared and its luminescence properties studied. With 324 nm light excitation, a blue emission band was observed due to the 5d 1→4f 1 transition of Ce3+. The average luminescence lifetime was calculated to be 5.437 µs and the CIE chromaticity coordinates were (0.162, 0.035). One may expect that K2Gd0.99Ce0.01Hf(PO4)3 can be used as a good blue phosphor for three-colour white-light-emitting diodes (WLEDs).
A new rare-earth polyborate, trisodium europium octaborate, Na3EuB8O15, was prepared using the high-temperature molten-salt method and structurally determined by single-crystal X-ray diffraction analysis. It crystallizes in the triclinic space group P\overline{1} and contains a one-dimensional [B8O15]∞ tube structure that is constructed from BO3 and BO4 polyhedra. The Eu3+ and Na+ cations reside in this structure to ensure cohesion and neutrality. The excitation spectra, emission spectra, decay time and Commission Internationale de l'Éclairage (CIE) chromaticity index of Na3EuB8O15 were studied. Under near-UV light excitation (393 nm), the polyborate shows an intense red emission, which mainly originates from the highest intensities of the 5D0→7F1 and 5D0→7F2 transitions.
A new potassium dysprosium polyborate, K 3 DyB 6 O 12 , has been prepared via the high-temperature molten salt method and structurally characterized by single-crystal X-ray diffraction analysis. The structure can be described as a three-dimensional framework composed of isolated bicyclic [B 5 O 10 ] 5À groups and Dy 3+ and K + ions. The Fourier transform IR (FT-IR) and ultraviolet-visible (UV-Vis) spectra were investigated. A series of K 3 Gd 1-x Dy x B 6 O 12 phosphors was prepared and their photoluminescence properties were studied. The K 3 -Gd 1-x Dy x B 6 O 12 phosphors exhibit a strong yellow emission band at 577 nm (the 4 F 9/2 ! 6 H 13/2 transition of Dy 3+ ) under UV excitation of 275 nm (the 8 S 7/2 ! 6 I J transition of Gd 3+ ), suggesting the occurrence of the energy transfer Gd 3+ !Dy 3+ . The optimized doping concentration of the Dy 3+ ion was 8 mol%. We may expect that K 3 Gd 1-x Dy x B 6 O 12 is a promising pale-yellow emission phosphor for visual displays or solid-state lighting.
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