A series of K3Gd1 x y(PO4)2:xCe3+,yTb3+phosphors are synthesized by the solid-sate reaction method.X-ray diffraction and photoluminescence spectra are utilized to characterize the structures and luminescence properties of the as-synthesized phosphors.Co-doping of Ce3+enhances the emission intensity of Tb3+greatly through an efficient energy transfer process from Ce3+to Tb3+.The energy transfer is confirmed by photoluminescence spectra and decay time curves analysis.The efficiency and mechanism of energy transfer are investigated carefully.Moreover,due to the nonconcentration quenching property of K3Tb(PO4)2,the photoluminescence spectra of K3Tb1 x(PO4)2:xCe3+are studied and the results show that when x=0.11 the strongest Tb3+green emission can be realized.
K3Gd(PO4)2:Tb3+ phosphors are synthesized by the solid reaction method,and the phases and luminescence properties of the obtained phosphors are well characterized.The emission spectra of K3Gd(PO4)2:Tb3+ exhibit the typical emissions of Tb3+.Concentration quenching of Tb3+ is not observed in K3Gd(PO4)2:Tb3+,likely because the shortest average distance of Tb3+–Tb3+ in K3Gd(PO4)2:Tb3+ is adequately long such that energy transfer between Tb3+–Tb3+ ions cannot take place effectively.This result indicates that K3Tb(PO4)2 phosphors have potential application in near ultraviolet(n-UV)-convertible phosphors for white light-emitting diodes.
A series of Ca4.99(PO4)3F:1%Eu3+,1%X(X = Li+,Au3+,and Bi3+) nanoparticles are prepared using hydrothermal method,with an average size of 33–62 nm. We study the improved photoluminescence properties of Ca4.99(PO4)3F:1%Eu3+ by co-doping with Li+,Au3+,and Bi3+ ions,respectively,and the enhancement of the emission intensities of Eu3+ is observed in these samples. The effects of Li+ acting as a charge compensator,Au3+ as a plasma surface sensitizer,and Bi3+ as an energy conversion agent are discussed. The results show Ca+4.99(PO4)3F:1%Eu3,1%X nanoparticles are a promising candidate as a red component for near-ultraviolet light-emitting diodes.
A series of single-phased Ca_(2)Al_(2)SiO_(7):Eu^(2+) phosphors were synthesized by the solid-state reaction. Their structure and photolumi-nescence properties were investigated by the X-ray powder diffraction (XRD) and excitation and emission spectra in detail. The emission spectra of Ca_2Al_2SiO_7:Eu^(2+) phosphors consisted of blue and green band located at419 and542 nm, respectively. The relative intensities of the blue and green emission changed with Eu^(2+) concentration and were sensitive to the excitation wavelength. The unique photoluminescence property originated from the 4f^(7)→4f^(6)5d transition of Eu^(2)+ at different energy levels, on which the effect of the crystal field strength was con-sidered to be tailed by adjusting the host composition.
A series of K3Gd(PO4)2:Tb3+,Sm3+ phosphors were synthesized through solid state reaction. By co-doping Tb3+ and Sm3+into K3Gd(PO4)2 host and singly varying the doping concentration of Sm3+, tunable colors from green to yellow and then to orange were obtained in K3Gd(PO4)2:Tb3+,Sm3+ phosphors under the excitation at 373 nm. The energy transfer process from Tb3+ to Sm3+ was verified through luminescence spectra and fluorescence decay curves. Moreover, the energy transfer mechanism was demonstrated to be the quadrupole-quadrupole interaction. The results indicated that K3Gd(PO4)2:Tb3+,Sm3+ phosphors could be a potential application for n-UV white light emitting diodes.
A novel red-emitting phosphor, CaYAl3O7 : Eu 3+ , Sm3+ , is synthesized by a combustion method at a low temperature (850℃), and the single phase of CaYAl3O7 is confirmed by powder X-ray diffraction measurements. The photoluminescence property results reveal that the red emission intensity of Eu3+ is strongly dependent on the Sm3+ concentration. Only the Eu 3+ luminescence is detected in the Eu 3+ -Sm3+ co-doped CaYAl3O7 phosphor with 393 nm excitation. However, under the characteristic excitation (402 nm) of Sm3+ , not only the Sm3+ emission but also the Eu 3+ emission are observed. A possible mechanism of the energy transfer between Sm3+ and Eu 3+ is investigated in detail.
We report the photoluminescence(PL) of Eu3+-doped glass with Bi3+as a sensitizer. The specific glass system with the strong enhancement of the red emission of Eu3+is obtained by adding a small number of Bi3+ions instead of increasing the Eu3+concentration. The emission band of Bi3+overlaps with the excitation band of Eu3+and the lifetime decay curves,resulting in a very efficient energy transfer from Bi3+to Eu3+. The probability of energy transfer is strongly dependent on Bi3+concentration. In addition, the intensity of 4f–4f transition is much stronger than that of a charge-transfer(CT) band in the excitation spectrum, which indicates that the Na2O–Ca O–Ge O2-Si O2 glass is a suitable red-emitting phosphor with high stability as a candidate for light-emitting diodes(LEDs).
The structure and photoluminescence (PL) properties of Sr3SiO5 : Sm3+ and Li+-doped Sr3SiO5 : Sm3+ red-emitting phosphors were investigated. Samples were prepared by the high-temperature solid-state method. PL spectra show that the concentration quenching occurs when the Sm3+ concentration is beyond 1.3 mol% in Sr3SiO5 : Sm3+ phosphor without doping Li+ ions. The concentration-quenching mechanism can be explained by the electric dipole-dipole interaction of Sm3+ ions. The incorporation of Li+ ions into Sr3SiO5 : Sm3+ phosphors, as a charge compensator, improves the PL properties. The lithium ions also suppress the concentration quenching in Sm3+ with concentration increased from 1.3 mol% to 1.7 mol%.
