A series of K3Gd1-x-y（PO4）2：xCe^3＋, yTb^3＋ 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 Ce^3＋ enhances the emission intensity of Tb^3＋ greatly through an efficient energy transfer process from Ce^3＋ to Tb^3＋. 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 non- concentration quenching property of K3Tb（PO4）2, the photoluminescence spectra of K3Tb1-x（PO4）2：xCe^3＋ are studied and the results show that when x = 0.11 the strongest Tb^3＋ green emission can be realized.
KaGd（PO4）2：Tb3＋ phosphors are synthesized by the solid reaction method, and the phases and lu- minescence properties of the obtained phosphors are well characterized. The emission spectra of KaGd（PO4）2：Tb3＋ exhibit the typical emissions of Tb3＋. Concentration quenching of Tb3＋ is not observed in KaGd（PO4）2：Tb3＋, likely because the shortest average distance of Tb3＋-Tb3＋ in KaGd（POn）2：Tb3＋ is adequately long such that energy transfer between Tb3＋-Tb3＋ ions cannot take place effectively. This re- sult indicates that KaTb（P04）2 phosphors have potential application in near ultraviolet （n-UV）-convertible phosphors for white light-emitting diodes.
A series of Ca499（PO4）3F：1%Eu^3＋, 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 Ca4.99（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 Ca2Al2SiOT：EU2＋phosphors were synthesized by the solid-state reaction. Their structure and photoluminescence properties were investigated by the X-ray powder diffraction （XRD） and excitation and emission spectra in detail. The emission spectra of Ca2Al2SiO7：Eu2＋ phosphors consisted of blue and green band located at 419 and 542 nm, respectively. The relative intensities of the blue and green emission changed with Eu2＋ concentration and were sensitive to the excitation wavelength. The unique photoluminescence property originated from the 4f^7→4f65d transition of Eu2＋ 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＋, ttmable colors from green to yellow and then to orange were obtained in K3Gd（POa）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 demon- strated to be the quadrupole-quadrupole interaction. The results indicated that K3Gd（POa）2：Tb3＋,Sm3＋ phosphors could be a potential application for n-UV white light emitting diodes.
A novel red-emitting phosphor, CaYA1307： Eu^3＋, Sm^3＋, is synthesized by a combustion method at a low temperature （850 ℃）, and the single phase of CaYA1307 is confirmed by powder X-ray diffraction measurements. The photoluminescence property results reveal that the red emission intensity of Eu^3＋ is strongly dependent on the Sm^3＋ concentration. Only the Eu^3＋ luminescence is detected in the Eu^3＋-Sm^3＋ co-doped CaYA1307 phosphor with 393 nm excitation. However, under the characteristic excitation （402 nm） of Sm^3＋, not only the Sm^3＋ emission but also the Eu^3＋ emission are observed. A possible mechanism of the energy transfer between Sm^3＋ and Eu3＋ is investigated in detail.
We report the photoluminescence（PL） of Eu^3＋-doped glass with Bi^3＋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 Eu^3＋ concentration. The emission band of Bi3＋overlaps with the excitation band of Eu^3＋ and the lifetime decay curves,resulting in a very efficient energy transfer from Bi^3＋ to Eu^3＋. The probability of energy transfer is strongly dependent on Bi^3＋ 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 Sr3 SiO5： Sm3＋ and Li＋-doped Sr3SiOs： 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 Sr3SiOs： 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 Sr3SiOs： 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 tool% to 1.7 tool%.
