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A reddish orange emissive long afterglow phosphors Ca2−xSnO4:xSm3+ (x = 0.001–0.05) are prepared by solid-state reaction in air atmosphere. The synthesized phosphors are characterized and analyzed by X-ray diffraction, photoluminescence spectra, afterglow decay curves, and absorption spectra. Under excitation at 407 nm, three emission peaks locate at 565, 610 and 654 nm, respectively, which can be assigned to the 4G5/2→6HJ (J = 5/2, 7/2, 9/2) transitions of Sm3+ ion. The fluorescent intensity and the afterglow characteristic depend on the concentration of Sm3+. The optimal Sm3+ concentration is x = 0.01. The CIE 1931 chromaticity coordinates of the emission and afterglow are (x = 0.6103, y = 0.3891) and (x = 0.5668, y = 0.4325) located in the range of reddish orange light emission. The afterglow decay curves of the Ca2SnO4:Sm3+ phosphor indicate both fast and slow decay components. The striking difference of the afterglow luminescence intensities of the phosphor after irradiation under 254 and 365 nm UV is discussed in deeply with absorption spectrum.

SrSi2O2N2:Eu2+ phosphors were prepared by a high temperature solid-state reaction method from the Eu2O3–SrCO3–Si3N4–Si system. The phase characteristics and luminescence properties of the samples synthesized with various starting composition of silicon powder were investigated in detail by mean of X-ray diffraction and fluorescence spectrophotometer analysis. Single-phase SrSi2O2N2:Eu2+ was successfully obtained avoiding the formation of an unknown phase, which usually exists from Eu2O3–SrCO3–Si3N4–SiO2 system. The comparison of different composition of starting materials [Si:Si3N4 = (1.5 + x)/3:(0.5−x) (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5)] indicates that different silicon powder content in starting materials plays an crucial role in phase and luminescence properties of SrSi2O2N2. The XRD diffraction intensity ratio of nitrogen-rich phase/oxygen-rich phase is increasing regularly with increasing x values in different starting composition of Si:Si3N4 = (1.5 + x)/3:(0.5−x) (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5). The emission intensity of the samples is gently enhanced with the increasing Si:Si3N4. This demonstrates that the SiO originated in the reaction of Si and CO2 is superior to SiO2 for preparation of SrSi2O2N2:Eu2+.

The red-emitting phosphors of CaBi2Ta2O9: Eu3+ and CaBi2Ta2O9: Eu3+/La3+ were prepared by the high-temperature solid-state reaction method. By using X-ray diffraction, the structural properties of powders have been analyzed. The photoluminescence excitation and emission spectra of CaBi2Ta2O9: Eu3+, and the dependence of luminescence intensity on doped Eu3+ ions concentration were investigated. The results show that CaBi2Ta2O9: Eu3+ can be efficiently excited by near-UV and blue light to realize an intense red luminescence (615 nm) corresponding to the electric dipole transition 5D0 → 7F2 of Eu3+ ions. Meantime, an enhancement of photoluminescence intensity was observed in La3+ ions doped CaBi2Ta2O9: Eu3+ phosphors. The CIE chromaticity coordinates of CaBi2Ta2O9: Eu3+ and CaBi2Ta2O9: Eu3+/La3+ are (0.6121, 0.3835) and (0.6141, 0.3821), corresponding to the hues of orange-red. The phosphors can be suggested to be a potential red-emitting phosphor for the application on white LEDs under irradiation of near-UV or blue chips.

SrSi2O2N2:Eu2+ phosphors were synthesized by a high temperature solid-state reaction method using Sr2SiO4 as the precursor. The effect of different Eu valence and partial substitution of Sr2+ by Ba2+ in Sr2SiO4 on the luminescence properties of SrSi2O2N2:Eu2+ was studied. Phase characteristics and luminescence properties of the samples were investigated in detail by mean of X-ray diffraction and fluorescence spectrophotometer analysis. The results revealed that there exist charge defects originated from the replacement of Sr2+ by Eu3+ in Sr2SiO4:Eu3+ and anion vacancies which likely occur in Sr1.95Ba0.05SiO4:Eu2+ due to partial substitutions of Sr2+ by Ba2+. The defects in the Sr2SiO4 play a role in luminescence properties of SrSi2O2N2:Eu2+. The emission intensity of the samples that use Sr2SiO4:Eu3+ and Sr1.95Ba0.05SiO4:Eu2+ as precursor was increased by 17% and 11% respectively when compared with that of using Sr2SiO4:Eu2+ as precursor(0.5 mol% Eu2+ concentration). And with the increasing Eu2+ concentration, the increasing degree of luminescence intensity of the samples declines rapidly. In additional, at 200 °C, 75–78% emission intensity of the phosphors measured at room temperature were maintained. Furthermore, partial replacement of Sr2+ by Ba2+ in samples can reduce thermal quenching.

The CaBi2Ta2O9 bismuth layered-structure ferroelectrics doped with rare earth ions Eu3+ and Tb3+, or co-doped with Eu3+/Tb3+ were prepared by the conventional solid-state reaction method. The microstructure and photoluminescence properties of CaBi2Ta2O9: Eu3+, CaBi2Ta2O9: Tb3+ and CaBi2Ta2O9: Eu3+/Tb3+ were investigated. The XRD patterns demonstrate that the rare earth ions have been effectively doped into CaBi2Ta2O9 host lattices. The photoluminescence properties of CaBi2Ta2O9 with different activator ions are researched in details. The novel red and green light emissions were observed under the excitation of blue and near-UV light. Notably, tunable emissions and a warm-white color have been achieved in the Eu3+ and Tb3+ co-doped CaBi2Ta2O9 powders. These results suggest that CaBi2Ta2O9: Eu3+, CaBi2Ta2O9: Tb3+ and CaBi2Ta2O9: Eu3+/Tb3+ could be novel luminescence materials. It is also expected that rare earth doped CaBi2Ta2O9 ferroelectrics can find potential applications in new multifunctional photoluminescence ferroelectric devices.

Eu 3+ doped CaBi 2 Ta 2 O 9 bismuth layered-structure ferroelectrics were synthesized by a solid state reaction method. Photoluminescence spectra exhibited a novel red-emitting centered at 615 nm under the excitation of 465 nm. The luminescence intensity of Ca 1− x Eu x Bi 2 Ta 2 O 9 increased with the increase of Eu 3+ concentration until x = 0.15. Then the luminescence intensity decreased with the continuous increase of Eu 3+ concentration. It is calculated that the thermal activation energy was 0.3 eV in the research on the thermal stability of the sample Ca 0.85 Eu 0.15 Bi 2 Ta 2 O 9 . In addition, an enhancement of luminescence intensity was observed in the sample doped with Sr (Ba, Nb).

A series of red-emitting phosphors of CaBi2Ta2O9:Pr3+ and CaBi2Ta2O9:Eu3+ were synthesized by the solid-state reaction method. The crystal structure and photoluminescence properties were investigated by X-ray diffraction (XRD) and photoluminescence spectra. The emission spectra showed that the red emission peaks were located at 622 nm for Pr3+ and 615 nm for Eu3+, respectively. The optimal doping concentrations for Ca1−xBi2Ta2O9:xPr3+ and Ca1−yBi2Ta2O9:yEu3+ were x=0.02 and y=0.15, respectively. The effect of fluxes (H3BO3, NH4F, CaCl2 and CaF2) and charge compensations (Li2CO3, Na2CO3 and K2CO3) on luminescent properties were investigated in detail. It was found that the relative emission intensity of Ca0.98Bi2Ta2O9:0.02Pr3+ with 10 mol.% H3BO3 flux was about 2.9 times higher than that of the sample without flux. The relative emission intensity of Ca0.7Bi2Ta2O9:0.15Eu3+, 0.15K+ was about the 2.1 times higher than that of Ca0.85Bi2Ta2O9:0.15Eu3+.