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The synthesis and photo-luminescence properties of Eu2+/Eu3+ or Ce3+/Eu3+ co-doped Sr 5 (BO 3) 3 F compounds are reported. Using the Sr 5 (BO 3) 3 F as the host, through the solid state reaction under the reductive atmosphere, Eu2+/Eu3+ and Ce3+/Eu3+co-doped samples were prepared. These compounds exhibit good photo-luminescence properties. Under the excitation of 376 nm, an unusual red orange emission coming from the Eu2+ ions can be obtained in Eu ions doped Sr 5 (BO 3) 3 F, which exhibits a broadband emission in the range of 450–800 nm with the peak at around 600 nm. At the same time, the characteristic f-f excitation and emission of Eu3+ can improve and adjust the Eu2+ emission in Eu3+/Eu2+ codoped Sr 5 (BO 3) 3 F. In addition, the adjustable luminescence properties from blue to white of Sr 5 (BO 3) 3 F:Ce3+, Eu3+ are investigated. The energy transfer behavior from Ce3+ to Eu3+ was confirmed. In the spectra of the co-doped samples, we can hardly observe the characteristic peak of Eu2+, because Ce4+ can oxidize Eu2+ to Eu3+, and Ce4+ itself is reduced to Ce3+. The CIE coordinates from (0.2758, 0.2420) to (0.3857, 0.3015) show Sr 5 (BO 3) 3 F:3%Ce3+, x%Eu3+ (x = 1,3,5,7,9) are in the white light emission region. All results demonstrate that the Sr 5 (BO 3) 3 F:Eu3+/Eu2+ and Sr 5 (BO 3) 3 F:Ce3+/Eu3+ phosphors have good application prospects for LED plant growth and white LED, respectively. The bond energy method was used to explain the reason why the Eu2+/Eu3+ ion instead of only Eu2+ and Ce3+/Eu3+ instead of Ce3+/Eu3+/Eu2+ can exist in the host Sr 5 (BO 3) 3 F. The theoretical analysis agree well with the experimental result. [ABSTRACT FROM AUTHOR]

A novel luminescent material Sr 5 (BO 3) 3 F:x%Eu3+ was synthesized for the first time by a high temperature solid phase reaction in an air atmosphere. The luminescence properties and site occupancy of Sr 5 (BO 3) 3 F:x%Eu3+ phosphors were studied. The XRD powder diffraction data imply that the series of targets synthesized are pure phases. After repeated experiments, it was found that the main peak position of the excitation and emission spectra changed greatly when the same concentration or different concentration of Eu3+ was doped, and two kinds of spectral phenomena appeared. First, the position of the broadband excitation peak is about 335 nm, and the position of the strongest emission peak belongs to the 5D 0 →7F 0 transition of Eu3+ at 572 nm. Second, the position of the broadband excitation peak is about 275 nm, and the position of the strongest emission peak belongs to the 5D 0 →7F 2 transition of Eu3+ at 619 nm. These imply that different lattice sites are occupied by Eu3+ in Sr 5 (BO 3) 3 F. At the same time, the unusually strong 5D 0 →7F 0 transition illustrates the presence of interstitial oxygen and anomalous crystal field strength in system. A theoretical calculation method of bond energy was applied to study the site occupancy of Eu3+, which shows that any one of Sr1, Sr2, and Sr3 has the possibility of being occupied by Eu3+. Therefore, our test results are consistent well with the theoretical analysis. [ABSTRACT FROM AUTHOR]

A novel adjustable dual excited emission Eu2+/Eu3+ co-doped Ca 4 Si 2 O 7 F 2 phosphor are reported. Unlike most of Eu2+ doped inorganic compounds, in the host lattice Ca 4 Si 2 O 7 F 2 , partial Eu3+ can still exist stably even in reducing atmosphere. The adjustable dual excited emission from blue light to red light can be found by changing the wavelength of excitation emission or the concentration of europium doped ion. The mechanism by which the two ions Eu2+ and Eu3+ can coexist in Ca 4 Si 2 O 7 F 2 is revealed through the bond energy theory. Eu2+ and Eu3+ in Ca 4 Si 2 O 7 F 2 system can be demonstrated to occupy the Ca1 lattice of Ca 4 Si 2 O 7 F 2. • The luminescence characteristics of Eu3+ in Ca 4 Si 2 O 7 F 2 matrix. • The dual-excitation emission can be achieved. • Calculation of lattice occupation by bond energy theory. [ABSTRACT FROM AUTHOR]

Eu3+ doped in SrGa 2 Si 2 O 8 particles can be an effective tool for designing dual-mode anti-counterfeiting materials based on their tunable luminescence transformation and excitation wavelength-dependent emission. The structure was analyzed by XRD and crystal structure diagram. Self-activated luminescence of SrGa 2 Si 2 O 8 host is luminescent in blue region. By adjusting the excitation wavelength, the sample's color changes from white to red. It is found that Eu3+ occupies the Sr ion lattice in SrGa 2 Si 2 O 8 matrix preferentially by band theory calculation. Our results demonstrate that this new phosphor shows a potential for the application of anti-counterfeiting materials. • The luminescence of host SrGa 2 Si 2 O 8. • The luminescence characteristics of Eu3+ in SrGa 2 Si 2 O 8 matrix. • The dual-excitation emission can be achieved. • Calculation of lattice occupation by bond energy theory. [ABSTRACT FROM AUTHOR]

To explore a new color-adjustable self-emitting in SrGa 2 Ge 2 O 8 :Eu phosphors, a series of experiments and characterization were carried out in this paper. Through a classic solid state method, we successfully synthesized the SrGa 2-y Ge 2-z O 8 :xEu (0 ≤ x, y, z ≦ 0.2) phosphors. The resulting SrGa 2-y Ge 2-z O 8 :xEu (0 ≤ x, y, z ≦ 0.2) phosphors had been structurally characterized by X-ray Powder Diffraction Refinements (XRD) and Energy Disperse Spectrometer (EDS). In the present study, it was found that under the excitation of 277 nm, by changing the concentration of doped europium ions, a series of color changes from cyan to white are obtained in SrGa 2 Ge 2 O 8. The energy transfer from the host to the Eu ions occurs. And the energy transfer ability from the host to Eu3+ were shown to be induced when aluminum was substituted to the nominal composition. The bond energy calculation result shows that the doped Sr2+, Ga3+, Ge4+ ions are substituted by Eu3+, Al3+ and Si4+, respectively, which is consistent with the XRD Rietveld refinement analysis. Also, the EDS analysis shows that atomic ratio is 10:19:20 for Sr/Ga/Ge in SrGa 2 Ge 2 O 8 , which is consistent with the XRD result. Diffuse reflection (DR) spectra and electronic structure display the energy band gap is 4.49 and 3.487eV, respectively. Excited by the 260 nm light, it presents a broad band peaks from 350 to 650 nm with the peak at 441 nm. When Al3+/Si4+ ions are doped in it, the red-shift of the matrix and the photoluminescence improvement of SrGa 2 Ge 2 O 8 : Eu can be found. • The luminescence characteristics and crystal structure of Eu in SrGa 2 Ge 2 O 8 matrix. • The dual-excitation emission can be achieved. • The lattice occupancy and energy transfer was studied. [ABSTRACT FROM AUTHOR]