The green emitting phosphors with general formula (La,Ce,Tb)MgAl11-xSi3x/4O19-3x/2Nx (0 ≤ x ≤ 0.5) were prepared with high temperature solid state reaction in reducing atmosphere with composition ...95%N2–5%H2. Co-doping with Si3N4 suppressed formation of secondary phase, and all samples showed pure crystalline LaMgAl11O19 phase. The La0.2MgAl11-xSi3x/4O19-3x/2Nx: 0.55Ce3+, 0.25 Tb3+ sample showed typical green emission related to the 5D4 to 7F5 transition of Tb ions, which was observed under 282 nm excitation owing to Ce–Tb transfer. Doping with nitrogen reduced the distance between Ce and Tb ions, which resulted in the improved luminescence as compared with undoped samples. Existing vacancy states reflected strongly in thermal dependence of luminescence of investigated phosphors. Finally, the luminous efficiency of lamps made of nitrided phosphors under ultraviolet excitation is higher than that of lamps without nitrogen-doped phosphors. This proves that doping with nitrogen is feasible way to improve luminous efficacies of currently commercially available phosphors.
•LaMgAl11-xSi3x/4O19-3x/2Nx:0.55Ce3+,0.25 Tb3+ phosphor is synthesized through high temperature solid-phase reaction.•Nitrogen is doped into the mixture to enhance the spectral characteristics and thermal stability of the phosphor.•Ce3+/Tb3+/N3+ doped LaMgAl11O19 phosphor in the UV-based luminous efficiency test.
A novel apatite structure phosphor Ca9La(PO4)5(GeO4)F2:Dy3+ (CLPGF:Dy3+) with a hexagonal lattice in the P63/m space group was synthesized via a facile solid state technique. The crystal and fine ...local structure as well as their photoluminescence properties were investigated in detail. The CLPGF:Dy3+ phosphor can absorb in the UV-vis spectral region of 290–475 nm and exhibit two intense emission bands centered at 485 and 580 nm, which ascribes to 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+, respectively. The concentration quenching of Dy3+ emission occurs via the energy transfer among the nearest-neighbor ions and the corresponding quenching mechanism was verified to be the dipole-dipole interaction. The quantum efficiencies of the phosphors were examined to be 72.9% and its luminescence intensity at 150 °C decreases to 93.8% and 98.6% of the initial value at room temperature, which corresponds to 4F9/2 to 6H15/2 transition and 4F9/2 to 6H13/2 transition of Dy3+ ions, respectively. Their interesting photoluminescence properties indicate that the CLPGF:Dy3+ phosphor is a promising white-emitting candidate for w-LEDs applications.
•A novel apatite-type Ca9La(PO4)5(GeO4)F2:Dy3+ phosphor has been synthesized.•Ca9La(PO4)5(GeO4)F2:Dy3+ is a promising white-emitting phosphor for LED.•The Ca9La(PO4)5(GeO4)F2:Dy3+ phosphor shows excellent thermal stability.
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•Novel double perovskite Ca2Gd0.5Nb1-xW5x/6O6:0.5Eu3+ phosphors were proposed.•The influence of W6+-doping concentration on luminescence properties was ...studied.•Ca2Gd0.5Nb1-xW5x/6O6:0.5Eu3+ red phosphors possess excellent luminescence performances.
High color rendering index (CRI), low correlation color temperature (CCT) and excellent thermal stability are crucial indicators to evaluate the practical applications of the white light-emitting diodes (WLEDs), and the red phosphor is a key component that restricts the performances of the WLEDs. Herein, we have designed a novel W6+-doping double perovskite compound, and a series of the proposed Ca2Gd0.5Nb1-xW5x/6O6:0.5Eu3+ (x = 0–0.2) red phosphors were synthesized by the traditional high-temperature solid-state method at 1300 ℃. The influences of W6+-doping concentration on the microstructures and luminescence properties of the phosphors were investigated in detail. It is found that the concentration of W6+ ion has little effect on the microstructures of the Ca2Gd0.5Nb1-xW5x/6O6:0.5Eu3+ phosphors, whereas significantly influences their luminescence properties. All the obtained Ca2Gd0.5Nb1-xW5x/6O6:0.5Eu3+ phosphors can be efficiently excited by 393 nm near-ultraviolet and 464 nm blue light, exhibiting a very strong red emission at 614 nm and a weak orange emission at 591 nm. Compared with Ca2Gd0.5NbO6:0.5Eu3+ phosphor, the excitation intensity and the emission intensity of the Ca2Gd0.5Nb1-xW5x/6O6:0.5Eu3+ (0 < x ≤ 0.2) phosphors are enhanced, displaying an initial increase and then decrease tendency with ascending x. Due to the optimal regulation effect in the local environment of Eu3+ and the band gap, the as-obtained Ca2Gd0.5Nb1-xW5x/6O6:0.5Eu3+ (x = 0.05) phosphor exhibits the best luminescence properties including CRI, thermal stability and quantum efficiency. Using the Ca2Gd0.5Nb1-xW5x/6O6:0.5Eu3+ (x = 0.05) phosphor as the red light component, the assembled WLED device shows bright warm-white light with the higher CRI of 91 and the lower CCT of 5386 K. This work provides an effective and facile strategy for boosting the luminescence of double perovskite oxide phosphors.
In this study, we developed the phosphate glass doped with CeF3 for scintillator applications. The phosphate glasses, 20Li2O−5Gd2O3–2ZrO2−(73-x) P2O5−xCeF3 were synthesized at different CeF3 ...concentrations by using the conventional melt-quenching technique. The density, molar volume, transmittance, photoluminescence (PL) and radioluminescence (RL) properties were investigated and quantified. The study found a positive correlation between the concentration of CeF3 with the density values and refractive index of the glass samples. The transmission spectra exhibited a red shift as the level of CeF3 increased. The emission spectra revealed a wide range of wavelengths resulting from the transition between the 5d and 4f transitions of the Ce3+ ion. The maximum intensity of emission for both PL and RL were observed at a concentration of 0.50 mol% CeF3. Moreover, the results of the emission spectra measured under Gd3+ excitation and the PL decay curves of Gd3+ in glass samples showed clearly evidence energy transfer (ET) from Gd3+ to Ce3+. The XPS spectra revealed the existence of phosphorus oxidation states. The XANES analysis revealed the existence of Ce3+ and Ce4+ in all glass samples, as evidenced by the appearance of peaks at approximately 5.728 keV for Ce3+, 5.732 keV and 5.739 keV for Ce4+. The scintillation efficiency of CeF3-doped phosphate glass with a concentration of 0.50 mol% was found to be 60.63% when compared to BGO crystal. Additionally, the decay time is extremely fast, varying from 17.52 to 25.93 ns, which is a critical attribute in the development of radiation detectors. In addition, X-ray imaging was conducted to investigate its potential efficacy in scintillator applications for X-ray imaging. The X-ray imaging investigation had a spatial resolution of 10 lp/mm with an MTF of 0.25. The results suggest that CeF3-doped phosphate glass has the potential to serve as a scintillator in X-ray imaging systems.
•The CeF3-doped phosphate glasses were synthesized using melt-quenching technique.•The PL and RL have the concentration quenching at 0.50 mol% of CeF3.•The photoluminescence decay time of CeF3-doped glass is in nanoseconds order.•The scintillation efficiency of 0.50 mol% of CeF3 was 60.63% compared to BGO crystal.•X-ray imaging was conducted for investigating scintillator applications.
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•Eu3+-activated LiSbO3 phosphor was synthesized by a solid-state reaction.•LiSbO3:Eu3+ demonstrates efficient pure red luminescence.•The lattice always provides two positions of Li+ ...and Sb5+ for Eu3+ doping.•Eu3+ ions mainly occupy Li sites, and only a few are doped in Sb5+ positions.
It is a challenge to accurately determine the exact location of the rare earth ion (RE) in the lattice when there are significant differences in radius, electronegativity and valence between the lattice cation and the corresponding RE activator in a host material. This study presents the findings on the luminescence and site occupancy of Eu3+ emission centers in the lithium antimonate LiSbO3 lattice. The phase-formation, structures, elemental composition, band transition characteristics, luminescence properties, and lifetimes of the Eu3+-doped phosphors were investigated. Eu3+-doped LiSbO3 exhibits a typical 5D0→7F2 red luminescence transition at 613 nm. Site-selective excitation, luminescence, and decay properties at the 7F0→5D0 transition wavelength were measured using a tunable pulsed narrow-band dye laser. Two Eu3+ luminescence centers in LiSbO3 were identified across the temperature range from 10 K to 300 K. The doping of RE(Eu3+) in LiSbO3 consistently occupies two crystallographic positions of Li+ and Sb5+. Furthermore, the probability of RE(Eu3+) ions preferentially occupying the Li+ (M) sites is notably high. The decay curves and luminescence lifetimes of the two Eu3+ centers were determined. Drawing from the experimental data, we discuss the potential defects induced by Eu3+ doping in LiSbO3 and the mechanism of charge compensation. These results could be instrumental in the advancement of new RE-activated luminescent materials or serve as a reference for investigating the specific positioning of RE ions within a phosphor lattice.
SrMg2La2W2O12:Eu3+ (SMLWO:Eu3+) phosphors are successfully synthesized via the high temperature solid-state method in air. We study the crystal structure and luminescence properties (e.g. the ...excitation and emission spectra, the concentration dependent spectra, and fluorescent lifetimes) of the samples. SMLWO:Eu3+ phosphor with excitation at 324, 396, and 466 nm emits red light due to the 5D0 → 7F0, 7F1, 7F2, 7F3, 7F4, and 7F5 transitions of Eu3+ ion. We investigate the influence of excitation wavelength and Eu3+ concentration on the luminescence properties of the samples. We confirm the optimal Eu3+ concentration (∼8 mol%) in SMLWO:Eu3+ phosphor via the concentration dependent emission spectra of samples, and explain the luminous mechanism of SMLWO:Eu3+ phosphor by using the energy level diagram and energy transfer of Eu3+ ion.
•SrMg2La2W2O12:Eu3+ are successfully synthesized via the high temperature solid-state method in air.•SrMg2La2W2O12:Eu3+ phosphor with excitation at 324, 396, and 466 nm emits red light.•The luminescence properties of the samples can be affected by the excitation wavelength.•The optimal Eu3+ concentration is ∼8 mol% in SMLWO:Eu3+ phosphor.
NaBa(PO3)3: x% Mn2+ (x = 1, 5, 10), NaBa(PO3)3: 5% Ag+ and co-doped NaBa(PO3)3: 5% Ag+, x% Mn2+ (x = 1, 5, 10) phosphate glass were successfully synthesized by a conventional melting-quenching ...method. These materials were prepared to improve the red luminescence of Mn2+ ions and the energy transfer efficiency between Ag+ and Mn2+ ions. XRD, DTA, FTIR, UV–visible–NIR and EPR were used to characterize the obtained materials. NaBa(PO3)3: x Mn2+(1, 5,10%) glasses exhibit a red emission band (under 410 nm) which increases strongly in intensity with increasing the Mn2+ content. Data extracted from emission and excitation spectra of NaBa(PO3)3: 5%Ag+ glass show the presence of two emitting centers in the UV range indicating the presence of two isolated Ag+ sites. From EPR and optical spectroscopic studies, the dominant ionic nature of the bonding and its octahedral site have been highlighted. The red emission intensity of Mn2+ in NaBa(PO3)3: 5% Ag+, x% Mn2+ (x = 1, 5, 10) phosphors increases with increasing the Mn2+ content upon excitation into the Ag + absorption band (250 nm) while that of Ag+ decreases significantly. This behavior is due to the energy transfer from Ag+ to Mn2+ ions confirmed by the spectral overlap between Mn2+ absorption and Ag+ emission. The red emission intensity is enhanced by 60% for 10% of Mn2+ compared to that of the glass upon direct excitation into the Mn2+ absorption band (410 nm).
•Optical and photoluminescence properties of Ag + -Mn2+ co-doped NaBa(PO3)3.•Efficiency of the energy transfer from Ag + to Mn2+.•Enhancement of the red emission of Mn2+.
Novel Mn4+-activated KLaMgWO6 red phosphors with different Mn4+ concentrations were successfully synthesized via a high-temperature solid-state reaction method. The phase formation, microstructure, ...photoluminescence properties, decay lifetimes and internal quantum efficiency were discussed to analyze the properties of the as-prepared phosphors. The samples belonged to monoclinic crystal system with enough WO6 octahedrons that provided suitable sites for Mn4+ ions. Upon the excitation of 348 nm, KLaMgWO6:Mn4+ phosphors gave bright far-red emission around 696 nm due to the 2Eg→4A2g transition of Mn4+ ions. The critical concentration of Mn4+ was 0.6 mol% and the concentration quenching mechanism belonged to electric multipolar interaction. Besides, the CIE chromaticity coordinates of the KLaMgWO6:0.6%Mn4+ phosphor were (0.7205, 0.2794) which located in deep red range, and its color purity reached up to 96.6%. The KLaMgWO6:0.6%Mn4+ sample also exhibited high internal quantum efficiency of 43%. All of the admirable optical properties indicate that the KLaMgWO6:Mn4+ phosphors can be applied to indoor plant growth illumination.
•GSBA glass doped with Ce3+/Eu3+ was successfully prepared.•Red shift in emission spectra of Ce3+ is caused by the increase of optical basicity.•Ce3+→Eu3+ mechanism based on GSBA system is electric ...quadrupole-quadrupole.•White light emission of Ce3+/Eu3+ co-doped glass is achieved and CCT is below 3300 K.
Through the method of conventional high-temperature melting, Ce3+/Eu3+doped GeO2-SiO2-BaO-Al2O3 (GSBA) glasses were fabricated. Photoluminescence spectrum, Fourier transform infrared spectroscopy, absorption spectrum, fluorescence attenuation time and CIE color coordinates were tested to investigate the optical properties and structure of glass. Using the formula of Dexter's energy transfer, the energy transfer from Ce3+ to Eu3+ was studied. The band gap as well as spacing between rare earth ion were obtained by theoretical calculation. The results show that the optimal cerium ion concentration of the Ce3+ doped and Ce3+/Eu3+ co-doped GSBA glass was consistent, which is 0.3 mol%. For the samples only doped with Ce3+, there has no significant changes of glass structure with increasing Ce3+ concentration, and multiple ligands of GeO4, GeO6, SiO4, SiO4&GeO4, AlO4 and AlO6 co-existed in glass structure. It is proved that there is energy transfer from Ce3+ to Eu3+ and the form of energy transmission is electric quadrupole-quadrupole transfer. What's noteworthy is that in Ce3+/Eu3+ double-doped glass, the prepared glass material can emit white light through changing the doped concentration of Eu3+ ion, and color temperature is all below 3300 K, which proves the application potential of Ce3+/Eu3+ co-doped germanosilicate glass in the field of warm white LED.
In this research, upconversion nanocrystals incorporated with MOR zeolite composites were synthesized using the desilicated MOR zeolite as a host for the in situ growth of NaREFsub.4 (RE = Y, Gd) ...Yb/Er nanocrystals. The structure and morphology of the composites were studied with XRD, XPS, and TEM measurements, and the spectral studies indicated that the subsequent thermal treatment can effectively improve the upconversion emission intensity of Ersup.3+. By using the NaYFsub.4:Yb/Er@DSi1.0MOR-HT composite that holds the strongest upconversion emission, a probe of UCNC@DSiMOR/BPEI was constructed with the modification of branched poly ethylenimine for the detection of Cusup.2+. It was indicated that the integrated emission intensity of Ersup.3+ shows a linear dependence with the logarithm value of the Cusup.2+ concentration ranging from 0.1 to 10 μM. This study offered a feasible method for the construction of UCNC@zeolite composites with enhanced upconversion emission, which may have a potential application as fluorescent probes for the detection of various metal ions by adjusting the doping luminescent center.
