Highly Stable Red Oxynitride β-SiAlON:Pr³⁺ Phosphor for Light-Emitting Diodes

Trivalent Pr3+-doped oxynitirde red phosphors β-SiAlON with composition Si6–zAlzOzN8–z:Prx (z = 0–2.0, x = 0.016) were synthesized by gas pressure sintering (GPS) at 1950 °C for 2 h. Red luminescence in the range 600–650 nm was detected upon excitation with 460 nm blue light, indicating that the phosphor can be excited by blue InGaN light-emitting diodes (LED). The crystallization and cell parameters of samples were investigated by powder X-ray diffraction (XRD), Rietveld refinement, and high-resolution transmission electron microscopy (HRTEM). Energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM) were further adopted to examine the effect of Al substitution on the microstructure. 27Al and 29Si solid-state nuclear magnetic resonance (NMR) data are consistent with SiN4–xOx and partially substituted AlN4–xOx tetrahedra. The temperature-dependent luminescence from the 1D2 and 3P0 states of Pr3+ were studied (10–573 K), and the integrated red emission from 600 to 650 nm increased with temperature (298–473 K). This unexpected phenomenon is proposed to be the result of two crossed excitation states in the configurational coordination diagram. This investigation reveals the superior characteristics of nitride compounds and the feasibility of doping Pr3+ into phosphor

Synthesis and VUV Photoluminescence Characterization of (Y,Gd)(V,P)O₄:Eu³⁺ as a Potential Red-emitting PDP Phosphor

YVO4:Eu3+-based phosphors in three series with compositions (Y1-xEux)(V1-zPz)O4, (Y0.95-yGdyEu0.05)(V0.4P0.6)O4 and (Y0.95-yEu0.05Gdy)(V1-zPz)O4 were synthesized and investigated as potential red-emitting phosphors for a plasma display panel (PDP). The optimal substitution proportions of P for V and Gd for Y were determined to be 60 and 20 mol %, respectively, for (Y0.95-yGdy)(V1-zPz)O4 doped with 5 mol % Eu3+. The vacuum ultraviolet PL and PLE spectra and chromaticity characteristics for the synthesized phosphors were measured and compared against those of a commercial red-emitting phosphor. Pumping the (Y,Gd)(P,V)O4:Eu3+ phosphors at a wavelength of 172 nm is more efficient than that at 147 nm. For VUV excitation at 147 nm, the CIE chromaticity coordinates for our red-emitting (Y1-yGdy)(V0.4P0.6)O4:Eu3+ are (0.6614,0.3286), as compared to (0.6443, 0.3613) for (Y,Gd)BO3:Eu3+ from Kasei Optonix Ltd. We suggest that the composition-optimized (Y0.75Gd0.20Eu0.05)(V0.4P0.6)O4 can serve as an alternative phosphor to replace a widely used red-emitting commercial phosphor such as (Y,Gd)BO3:  Eu3+ or Y2O3:  Eu3+

Synthesis and VUV Photoluminescence Characterization of (Y,Gd)(V,P)O₄:Eu³⁺ as a Potential Red-emitting PDP Phosphor

YVO4:Eu3+-based phosphors in three series with compositions (Y1-xEux)(V1-zPz)O4, (Y0.95-yGdyEu0.05)(V0.4P0.6)O4 and (Y0.95-yEu0.05Gdy)(V1-zPz)O4 were synthesized and investigated as potential red-emitting phosphors for a plasma display panel (PDP). The optimal substitution proportions of P for V and Gd for Y were determined to be 60 and 20 mol %, respectively, for (Y0.95-yGdy)(V1-zPz)O4 doped with 5 mol % Eu3+. The vacuum ultraviolet PL and PLE spectra and chromaticity characteristics for the synthesized phosphors were measured and compared against those of a commercial red-emitting phosphor. Pumping the (Y,Gd)(P,V)O4:Eu3+ phosphors at a wavelength of 172 nm is more efficient than that at 147 nm. For VUV excitation at 147 nm, the CIE chromaticity coordinates for our red-emitting (Y1-yGdy)(V0.4P0.6)O4:Eu3+ are (0.6614,0.3286), as compared to (0.6443, 0.3613) for (Y,Gd)BO3:Eu3+ from Kasei Optonix Ltd. We suggest that the composition-optimized (Y0.75Gd0.20Eu0.05)(V0.4P0.6)O4 can serve as an alternative phosphor to replace a widely used red-emitting commercial phosphor such as (Y,Gd)BO3:  Eu3+ or Y2O3:  Eu3+

Electronic and Vibrational Absorption Spectra of NH₂ in Solid Ne

Irradiation of ammonia dispersed in solid neon near 4 K with tunable far-ultraviolet light from a synchrotron yielded amidogen, NH2, and imidogen, NH, radicals as products. The electronic absorption spectra of amidogen radicals in isotopic variants NH2, NHD, and ND2 were recorded in the visible and near-ultraviolet regions after photolysis of NH3 and ND3. The infrared absorption lines of NH2 associated with vibration-rotational levels of vibrational modes ν1 at 3234.3 (00,0–10,1), 3244.9 (00,0–11,1), and 3249.3 cm–1 (00,0–11,0), and ν2 at 1498.7 (10,1–11,1), 1509.5 (11,0–10,1), 1516.5 (00,0–10,1), 1528.6 (00,0–11,1), and 1533.7 cm–1 (00,0–11,0) were unambiguously identified according to the results of experiments with deuterium isotopes. The 00,0–00,0 lines of ν1 and ν2 for NH2 were derived to be at 3213.5 and 1494.6 cm–1 in solid neon

Nitrogen-Vacancy Centers in Diamond for High-Performance Detection of Vacuum Ultraviolet, Extreme Ultraviolet, and X‑rays

Fluorescent nanodiamonds (FNDs) containing nitrogen-vacancy (NV) centers as built-in fluorophores exhibit a nearly constant emission profile over 550–750 nm upon excitation by vacuum-ultraviolet (VUV), extreme ultraviolet (EUV), and X-radiations from a synchrotron source over the energy (wavelength) range of 6.2–1450 eV (0.86–200 nm). The photoluminescence (PL) quantum yield of FNDs increases steadily with the increasing excitation energy, attaining a value as great as 1700% at 700 eV (1.77 nm). Notably, the yield curve is continuous, having no gap in the VUV to X-ray region. In addition, no significant PL intensity decreases were observed for hours. Applying the FND sensor to measure the absorption cross-sections of gaseous O2 over 110–200 nm and comparing the measurements with the sodium-salicylate scintillator, we obtained results in agreement with each other within 5%. The superb photostability and broad applicability of FNDs offer a promising solution for the long-standing problem of lacking a robust and reliable detector for VUV, EUV, and X-radiations

Identification of Nitrogen Defects in Diamond with Photoluminescence Excited in the 160–240 nm Region

Photoluminescence (PL) spectra of natural diamond powders of type IaAB at 300 and 13 K were excited with synchrotron radiation in the wavelength range of 150–260 nm. The spectral features observed in the excitation spectra at 13 K show four vibrational progressions related to nitrogen defects in diamond: A, B, B′, and N3. Progression A has a spacing of 1258 ± 40 cm–1, associated with the N2 (or A) center; progression B has a spacing of 1181 ± 40 cm–1 and progression B′ has a spacing of 744 ± 40 cm–1 related to the N4 (or B) center; and progression N3 has a spacing of 1417 ± 40 cm–1 associated with the N3 center. The PL of these defects comprise continuous emission with two broad lines with maxima of ∼420 and 469 nm at 300 K. Upon excitation with light at wavelengths of <200 nm, the distinct zero-phonon lines of N3 and N4 centers in diamond at a temperature of 13 K become prominent at 416.0 and 491.2 nm, respectively. The vibrational progressions in the photoluminescence excitation (PLE) spectra of N2, N3, and N4 centers in diamond of type IaAB at 13 K are identified for the first time. We suggest the use of PL spectra excited in the region of 160–240 nm to analyze and identify the type of diamond

Imaging Extreme Ultraviolet Radiation Using Nanodiamonds with Nitrogen-Vacancy Centers

Extreme ultraviolet (EUV) radiation with wavelengths of 10–121 nm has drawn considerable attention recently for its use in photolithography to fabricate nanoelectronic chips. This study demonstrates, for the first time, fluorescent nanodiamonds (FNDs) with nitrogen-vacancy (NV) centers as scintillators to image and characterize EUV radiations. The FNDs employed are ∼100 nm in size; they form a uniform and stable thin film on an indium–tin–oxide-coated slide by electrospray deposition. The film is nonhygroscopic and photostable and can emit bright red fluorescence from NV0 centers when excited by EUV light. An FND-based imaging device has been developed and applied for beam diagnostics of 50 nm and 13.5 nm synchrotron radiations, achieving a spatial resolution of 30 μm using a film of ∼1 μm thickness. The noise equivalent power density is 29 μW/(cm2 Hz1/2) for the 13.5 nm radiation. The method is generally applicable to imaging EUV radiation from different sources

All-In-One Light-Tunable Borated Phosphors with Chemical and Luminescence Dynamical Control Resolution

Single-composition white-emitting phosphors with superior intrinsic properties upon excitation by ultraviolet light-emitting diodes are important constituents of next-generation light sources. Borate-based phosphors, such as NaSrBO₃:Ce³⁺ and NaCaBO₃:Ce³⁺, have stronger absorptions in the near-ultraviolet region as well as better chemical/physical stability than oxides. Energy transfer effects from sensitizer to activator caused by rare-earth ions are mainly found in the obtained photoluminescence spectra and lifetime. The interactive mechanisms of multiple dopants are ambiguous in most cases. We adjust the doping concentration in NaSrBO₃:RE (RE = Ce³⁺, Tb³⁺, Mn²⁺) to study the energy transfer effects of Ce³⁺ to Tb³⁺ and Mn²⁺ by comparing the experimental data and theoretical calculation. The vacuum-ultraviolet experimental determination of the electronic energy levels for Ce³⁺ and Tb³⁺ in the borate host regarding the 4f–5d and 4f–4f configurations are described. Evaluation of the Ce³⁺/Mn²⁺ intensity ratios as a function of Mn²⁺ concentration is based on the analysis of the luminescence dynamical process and fluorescence lifetime measurements. The results closely agree with those directly obtained from the emission spectra. Density functional calculations are performed using the generalized gradient approximation plus an on-site Coulombic interaction correction scheme to investigate the forbidden mechanism of interatomic energy transfer between the NaSrBO₃:Ce³⁺ and NaSrBO₃:Eu²⁺ systems. Results indicate that the NaSrBO₃:Ce³⁺, Tb³⁺, and Mn²⁺ phosphors can be used as a novel white-emitting component of UV radiation-excited devices

Controlling The Activator Site To Tune Europium Valence in Oxyfluoride Phosphors

A new Eu³⁺-activated oxyfluoride phosphor Ca₁₂Al₁₄O₃₂F₂:Eu³⁺ (CAOF:Eu³⁺) was synthesized by a solid state reaction. Commonly red line emission was detected in the range of 570–700 nm. To achieve the requirement of illumination, this study revealed a crystal chemistry approach to reduce Eu ions from 3+ to 2+ in the lattice. Replacing Al³⁺–F^– by the appreciate dopant Si⁴⁺–O^2– is adopted to enlarge the activator site that enables Eu³⁺ to be reduced. The crystallization of samples was examined by powder X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). Photoluminescence results indicated that as-synthesized phosphors Ca₁₂Al_{14‑<i>z</i>}Si_<i>z</i>O_32+<i>z</i>F_2–<i>z</i>:Eu (<i>z</i> = 0–0.5, CASOF:Eu) display an intense blue emission peaking at 440 nm that was produced by 4f–5d transition of Eu²⁺, along with the intrinsic emission of Eu³⁺ under UV excitation. Moreover, the effect of Si⁴⁺–O^2– substitution involved in the coordination environment of the activator site was investigated by further crystallographic data from Rietveld refinements. The ¹⁹F solid-state nuclear magnetic resonance (NMR) data were in agreement with refinement and photoluminescence results. Furthermore, the valence states of Eu in the samples were analyzed with the X-ray absorption near edge structure (XANES). The quantity of substituted Si⁴⁺–O^2– tunes chromaticity coordinates of Ca₁₂Al_{14–<i>z</i>}Si_<i>z</i>O_32+<i>z</i>F_2–<i>z</i>:Eu phosphors from (0.6101, 0.3513) for <i>z</i> = 0 to (0.1629, 0.0649) for <i>z</i> = 0.5, suggesting the potential for developing phosphors for white light emitting diodes (WLEDs). Using an activator that is valence tunable by controlling the size of the activator site represents a hitherto unreported structural motif for designing phosphors in phosphor converted light emitting diodes (pc-LEDs)

Selective Growth of Boron Nitride Nanotubes by the Plasma-Assisted and Iron-Catalytic CVD Methods

Boron nitride nanotubes (BNNTs) were selectively synthesized on patterned bilayer (Fe/Al) catalysts by the plasma-assisted chemical vapor deposition (PACVD) method. The as-grown nanotubes comprise both coaxial and cup-stacking tubular structures. Optical transitions on cup-stacking BNNTs are investigated for the first time. The observed red-shift of free excitonic luminescence was attributed to the excitonic recombination in terms of defect trapping in the tube’s surface. The O2 additives during the synthetic process were found to balance the excess H radicals that in turn enhance the growth yield of BNNTs. Moreover, our elemental mapping results provide direct evidence of the metal catalytic mechanism and the influence of the as-formed Al2O3 underlayer