Transitions Of Pr3 Research Articles

UVC Emission Devices Based on Alternating Current Inorganic Electroluminescence Using Y2SiO5:Pr3+ Phosphors

Ultraviolet C (UVC: 200-280 nm) lighting is urgently required for a number of sterilization applications such as water and air disinfection, food processing, and medical sterilization. Compared to other UVC emission sources, AC-driven inorganic phosphor electroluminescent (EL) devices are appealing due to their wide viewing angle, fast response time, low power consumption, high contrast, simple manufacture, and cost effectiveness. Although the luminance of inorganic phosphor EL devices is typically low, it is sufficient for most low-cost lighting and large-area display applications. In addition, inorganic phosphor EL devices have the advantage of emitting light without generating much heat. In this study, UVC emission was demonstrated through EL devices using a UVC phosphor. Pr3+-doped Y2SiO5 (Y2SiO5:Pr3+) is used for UVC light, Y2SiO5:Pr3+ phosphor shows a broad UVC emission at 280 nm from the f-d transition of Pr3+ ions as well as a sharp red emission at 610 nm from the f-f transition of Pr3+ ions. The phosphors were synthesized in three types to fabricate EL devices. The Y2SiO5:Pr3+ powder, film, and nano-powder formed the phosphor layers of EL devices by screen printing, spin coating, and electrophoretic deposition, respectively. In order to emit UVC light, patterned gold was used for transparent electrodes of the devices instead of conventional indium tin oxide (ITO), which absorbs the UV region. The EL devices were demonstrated in two types: powder EL and electrolyte EL. The fabricated EL devices showed a wide range of UVC emission from 260 nm to 330 nm. Finally, luminescent and electrical analysis of each device was performed to analyze the characteristics.

Time-dependent electrical and electroluminescence properties of In-substituted CaSnO3 and CaSnO3:Pr thin films prepared by a chemical solution deposition method

CaSnO3, CaSn0.9In0.1O3−δ, and Ca0.995Pr0.005Sn0.9In0.1O3−δ thin films sandwiched between (In0.975Sn0.025)2O3−δ thin-film electrodes were prepared by a chemical solution deposition method. The electric and electroluminescence properties were investigated by applying dc (direct current) voltages to the films. No appreciable current was detected for the CaSnO3 thin film. When constant dc voltage was applied to the CaSn0.9In0.1O3−δ and the Ca0.995Pr0.005Sn0.9In0.1O3−δ thin films, current was close to zero just after applying the voltage, increased with increasing time at the beginning, reached a maximum at a certain time, and then decreased with increasing time. The current increased by annealing at 673 K in air and decreased reversibly by quenching from 1323 K. Ca0.995Pr0.005Sn0.9In0.1O3−δ thin film showed reddish white electroluminescence due to f-f transitions of Pr3+ ions. The time dependence of the luminance was similar to that of the current. The results were discussed in relation to oxygen absorption and desorption at high temperatures and electromigration of oxygen vacancies at room temperature.

Interconfigurational d-f luminescence of Pr3+ ions in praseodymium doped Li6Y(BO3)3 single crystals

Luminescence properties of undoped Li6Y(BO3)3 (LYB) crystals grown by the Bridgman method as well as undoped and praseodymium doped LYB crystals grown by the Czochralski method were studied under excitation by ultraviolet light, synchrotron radiation and electron beam in the temperature region of 5–300 K. The emission bands peaking at 4.8, 3.76 and 2.95 eV were found in undoped Czochralski-grown crystals, while the band at 3.34 eV was dominant in the Bridgman-grown crystals. These bands are presumably ascribed to excitons localized at regular and defect-perturbed lattice sites. Intense emission bands peaking at 4.75, 4.50, 4.17 and 3.98 eV were discovered in Pr doped crystals at low temperatures and related to the interconfigurational 4f15d1 → 4f2 radiative transitions in Pr3+ ions. The structure of the emission spectrum is shown to be determined by the 3H4, 3H5, 3H6, 3F2, 3F3, 3F4 terms of the Pr3+ ion. The characteristic decay time of the 4f15d1 → 4f2 emission is τ = 24 ns at low temperatures, however, it shortens to 9 ns by room temperature due to a strong thermal quenching. The study of glow curves and spectra of thermostimulated luminescence in Li6Y(BO3)3:Pr crystal irradiated by 10-keV electron beam shows that Pr3+ ions do not participate in an electron-hole recombination process.

Structural and luminescence properties of transparent borate glass co-doped with Gd3+/Pr3+ for photonics application

A new glass system of lithium borate doped with Gd2O3 and Pr2O3 has been fabricated using a conventional melt quenching technique. The physical parameters, such as density, molar volume, and refractive index, were measured and found to increase as the concentrations of lanthanide oxide (Gd2O3 and Pr2O3) in the glass increased, revealing the underlying structural changes. According to the results of XRD and FTIR, the synthesized glasses exhibited an amorphous structure, and borate complexes served as the triangular BO3, tetrahedral BO4, and OH group amounts in oxide glass. The photoluminescence (PL) spectra show characteristic emission bands resulting from f-f transitions of Pr3+ ions. The strongest emission occurred at 603 nm, corresponding to the transition from the 1D2 state to the 3H4 state. The optimal concentration of Gd2O3 for maximizing emission intensity was found to be 5.0 mol%, and this concentration will be used in the next experiment with varying Pr2O3 concentrations. In the subsequent experiment, emission spectra were recorded by exciting the glass with light at wavelengths of 445 nm, 469 nm, and 483 nm. The resulting emission spectra displayed the characteristic pattern associated with the emission of Pr3+. This emission peak at 603 nm represented the strongest intensity in the spectra, which is a common characteristic of Pr3+ emission. The emission intensity of the glasses initially increases with increasing concentrations of Pr2O3 up to 0.3 mol%, but beyond this concentration, the emission intensity starts to decrease. This behavior indicates the occurrence of a quenching effect at the 0.3 mol% concentration of Pr2O3. X-ray absorption near-edge structure (XANES) analysis confirmed that praseodymium ions were predominantly in the 3 + oxidation state. The chemical composition of the created glass was confirmed to be suitable for photonics applications.

Люминесцентная спектроскопия фосфатов, легированных ионами Pr-=SUP=-3+-=/SUP=-, облученных быстрыми электронами и реакторными нейтронами

This paper reports the spectroscopic properties of phosphates KLuP2O7, Sr9Sc(PO4)7, K3Lu(PO4)2, doped with Pr3+ ions. Photoluminescence (PL) spectra under selective excitation with UV photons, PL excitation spectra, and decay kinetics of pulsed cathodoluminescence are studied. Recordings of luminescence spectra were done with non-irradiated samples and after their irradiation with fast electrons (E = 10 MeV) or fast reactor neutrons. Three typical channels of electronic excitations radiative relaxation have been identified: interconfigurational d−f transitions, intraconfigurational f−f transitions in Pr3+ ions and luminescence associated with defects. After irradiation, significant changes in the luminescence characteristics were observed: a redistribution of the intensity of the intraconfigurational d−f transitions, an increase in the luminescence yield of defects and the manifestation of new emission centers. The formation of radiation-induced defects presumably occurs due to the formation of complexes consisting of phosphorus and oxygen atoms.

Spectroscopic Properties of Pr3+, Tm3+, and Ho3+ in Germanate-Based Glass Systems Modified by TiO2

In this paper, the effect of the GeO2:TiO2 molar ratio in glass composition on the spectroscopic properties of germanate glasses was systematically investigated. The visible luminescence bands associated with characteristic 1D2 → 3H4 (red), 5S2, 5F4 → 5I8 (green), and 1D2 → 3F4 (blue) transitions of Pr3+, Ho3+, and Tm3+ ions in systems modified by TiO2 were well observed, respectively. It was found that the luminescence intensity of glasses containing Pr3+ and Ho3+ ions increases, whereas, for Tm3+-doped systems, luminescence quenching with increasing content of TiO2 was observed. Based on Commission Internationale de I'Eclairage (CIE) chromaticity coordinates (x, y) analysis, it was demonstrated that the value of chromaticity coordinates for all glasses depends on the GeO2:TiO2 molar ratio. The addition of TiO2 to system compositions doped with Tm3+ ions shifts the (x, y) to the center of the CIE diagram. However, chromaticity coordinates evaluated for glasses containing Pr3+ ions move to a purer red color. Our results confirm that the spectroscopic properties of the studied glasses strongly depend on TiO2 content. Moreover, it can be stated that germanate-based glass systems modified by TiO2 can be used for optoelectronics in RGB technology as red (Pr3+), green (Ho3+), and blue (Tm3+) emitters.

Synthesis, structure and luminescence characteristics of La3Ga5SiO14:Pr3+ phosphors

In this study, we synthesized series of La3Ga5SiO14:Pr3+ phosphors by high-temperature solid-state reactions. For the synthesized phosphors, X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive spectrum (EDS), Raman, infrared (IR), absorption, photoluminescence (PL) and photoluminescence excitation (PLE) characterizations and decay characteristics were performed. The XRD patterns indicate that the synthesized phosphors have the same D32 (P321) structure with La3Ga5SiO14 host. The SEM image and EDS pattern show the irregular morphology and the combined La, Ga, Si, O and Pr elements for the synthesized phosphors. The room temperature Raman and IR spectra show that the phonon modes of the La3Ga5SiO14:Pr3+ phosphors follow the overall mode distributions of La3Ga5SiO14 and no appreciable changes in the phonon properties are observed, indicating that the force fields in the La3Ga5SiO14:Pr3+ lattice are not strongly altered by Pr3+ doping. The UV-Vis absorption spectra show that the phosphors contain a strong absorption band and several moderate bands resulting from the 4f-5d and f-f transitions of Pr3+ ions, respectively. La3Ga5SiO14:Pr3+ phosphors produce white light when λex = 255 nm. On the basis of emission data, the concentration quenching mechanism of the Pr3+ emission was speculated as the dipole-dipole interaction. The decay time and thermal stability were investigated, and the CIE coordinates with the corresponding correlated color temperatures were also calculated.

AC‐Driven Ultraviolet‐C Electroluminescence from an All‐Solution‐Processed CaSiO3:Pr3+ Thin Film Based on a Metal‐Oxide‐Semiconductor Structure

AbstractAn ultraviolet (UV) light source is continuously required for applications of sterilization as well as industrial value. In particular, research on materials and devices emitting UV‐C radiation in the range from 210 to 280 nm is very meaningful and challenging work. Herein, UV‐C electroluminescence (EL) from an all‐solution processed CaSiO3:Pr3+ (CSO) thin film is reported for the first time. The CSO thin film is formed on a Si substrate (size of 13 × 13 mm2), and structurally, the UV‐C EL device has a metal‐oxide‐semiconductor (MOS) shape consisting of CSO and interlayered SiOx of 100 and 150 nm thickness, respectively, on Si. The emission and electrical properties of the UV‐C EL device are investigated under an alternating current system. The results reveal UV‐C emission peaking at 276 nm attributed to the 4f5d‐3H(F)j transition of Pr3+ ions within CSO, with a maximum output optical power of 8.37 µW cm−2 (power efficiency of 0.15%) at an operating voltage of 40 Vop (50 Hz). The work can provide a feasible method for realizing large‐area UV‐C‐emitting devices based on the MOS structure.

Long afterglow yellow luminescence from Pr3+ doped SrSc2O4

A yellow emitting long afterglow luminescence material SrSc2O4:Pr3+ was successfully prepared by solid state reaction method. SrSc2O4:Pr3+ phosphor shows a long afterglow luminescence peak at about 495, 545, 621, 630 and 657 nm, respectively, corresponding to the f–f transitions of Pr3+. The afterglow chromaticity coordinates of SrSc2O4:1 at%Pr3+ were calculated to be (0.35, 0.41), indicating that the afterglow emission is close to the light of yellow region. And, the afterglow luminescence of the optimal sample doped by 1 at%Pr3+ can persist for over 3 h. The thermoluminescence results suggest that there are three types of traps with depth of 0.61, 0.69 and 0.78 eV exiting for all the samples, which are produced by the addition of Pr3+ ions. The trap density of SrSc2O4:1 at%Pr3+ is the maximum when the incorporation of Pr3+ ions reaches 1 at%, which thus results in the longest afterglow luminescence. All the results indicate that SrSc2O4:Pr3+ can be a potential candidate of novel long afterglow phosphors.

Luminescent behavior of pulsed laser deposited Pr doped ZnO thin films

Highly c-axis oriented, single-phase praseodymium doped ZnO (PZO) thin films were pulsed laser deposited on c-Al2O3 substrate under different oxygen pressure conditions. Photoluminescence spectra revealed the presence of intense band-edge emission, low intensity defect related emission in the Jacobian transformed wavelength to energy plots in the UV–visible region. The presence of a distinct peak at 2.79 eV correlates with the emission from Pr3+ ions, ensuring energy transfer between the host and Pr3+ ions under indirect excitation. Different narrow line width, intra-4fn-shell transitions of Pr3+ ions from 3P0,3P1 and 1D2 energy states were observed under direct excitation and found to depend on the ambient oxygen pressure maintained during deposition. All the PZO thin films were found to be ~90% transparent in the region between 400 and 800 nm. X-ray photoelectron emission studies of these films ensured the occurrence of Pr as Pr3+ ions in the ZnO matrix.

Photoluminescence and afterglow behavior of orange-reddish Pr3+-activated Sr3Al2O6 phosphor

The orange-reddish Sr3Al2O6:Pr3+ samples were prepared using solid state reaction in air and the photoluminescence properties of the phosphors were investigated. The as-prepared phosphors were studied systematically by X-ray diffraction, scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS), photoluminescence (PL) spectra, afterglow decay curves, thermoluminescence (TL) glow spectra, X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). The luminescence of Pr3+-activated Sr3Al2O6 exhibited a strong emission peak at 611 ​nm under 246 ​nm excitation arising from the intrinsic f-f transition of Pr3+ as an emitting centre. The ions of Pr3+ acted as not only the activators but also the providers of traps. The doping concentration of Pr3+ has a significant effect on the photoluminescence and long afterglow luminescence. The TL process and possible luminescence working mechanism of the Sr3Al2O6:Pr3+ were discussed in detail. The suitable and effective trap depths as well as the high concentration of defects for Sr3Al2O6 phosphors were obtained though the introduction of Pr3+ ions, greatly extending the lifespan of the electron-hole pair in the lattices for the improvement of the luminescent properties of Sr3Al2O6 long afterglow phosphors.

Structural, thermal and broadband NIR emission properties of Nd3+/Pr3+/Ag NPs co-doped tellurite glass

Nd3+/Pr3+ co-doped tellurite glasses containing metallic Ag NPs were synthesized by melt-quenching and heat-treating techniques. The amorphous structural nature, fundamental vibrational units and good thermal stability of the prepared tellurite glasses were confirmed by X-ray diffraction (XRD) pattern, Raman spectrum and differential scanning calorimeter (DSC) curve, respectively. The precipitated Ag NPs in a glass matrix with an average diameter ∼5 nm were revealed by transmission electron microscopy (TEM) image, and the radiative property of Nd3+ and Pr3+ ions was evaluated from the absorption spectrum by Judd-Ofelt theory. Under the excitation of 488 nm Xenon lamp, two broadband near-infrared emissions covering 800-1100 nm and 1250-1650 nm ranges were observed from the fluorescence spectrum. The former originated from the transitions of Pr3+:3P1,0→1G4, Pr3+:1D2→3F4,3, Nd3+:4F3/2→4I11/2 and Nd3+:4F3/2→4I9/2, while the latter was contributed by the Pr3+:1G4→3H5, Pr3+:1D2→1G4, Pr3+:3F3→3H4 and Nd3+:4F3/2→4I13/2 transitions. With the introduction of Ag NPs, the emission intensity of two broadband near-infrared emissions was further enhanced, in which the peak emission intensity of 1250-1650 nm band was increased by about 56% and the FWHM is up to 250 nm. The obtained results indicate that Nd3+/Pr3+/Ag NPs co-doped tellurite glass has great potential in realizing ultra-broadband near-infrared emission covering O-, E- and S-bands simultaneously.

Luminescence of 5d–4f transitions of Pr3+ in natural fluorite CaF2, anhydrite CaSO4 and apatite Ca5(PO4)3F

Natural fluorite, anhydrite and apatite under deep UV excitation exhibits several narrow emission bands in the spectral range of 225–300 nm with the strongest peaks at 230–240 nm and 260–290 nm and with half-widths of 20–30 nm. They are characterized by narrow excitation band peaking at 220 nm and very short decay times of 20–50 ns. Those spectral-kinetic parameters enable their interpretation as 4f5d–4f transitions in Pr3+ luminescence center. Such kind of luminescence has been studied extensively over the past several decades in synthetic phosphors, including those which are analogous to natural compounds, but it is the first time 5d–4f luminescence transitions of Pr3+ is being proved in minerals.

Pr3+ doped BaNb2O6 reddish orange emitting phosphor for solid state lighting and optical thermometry applications

A novel reddish-orange emitting BaNb2O6: Pr3+ phosphor was synthesized by conventional solid-state reaction method and its structural, morphological, optical properties and temperature dependent photoluminescence properties were investigated. The Le Bail profile matching of XRD patterns confirmed the orthorhombic phase presence and the corresponding cell parameters were calculated.Through a profound investigation of UV–visible diffuse reflectance spectra, a decrease in optical-band gap energy and an increase in Urbach tail width were noticed in doped sample as compared to undoped sample. Under the blue light excitation, the emission spectra exhibit peaks in reddish-orange region due to intra f-f transitions of Pr3+ ions. Strong covalence between Pr3+ and O2- was estimated by calculating nephelauxetic ratio, bonding parameter and covalency using the excitation spectra. The involvement of intervalence charge transfer (IVCT) state results in nonradiative relaxation increase, for which the emission peak intensities decreased with increase in temperature. The configurational coordinate model was used to demonstrate this phenomenon. The fluorescence intensity ratio technique was utilized for temperature sensing applications. The suitable CIE coordinates and significant temperature dependent PL makes the BaNb2O6: Pr3+ material to be a potential candidate for contributing red component in WLED and temperature sensing applications.

Peculiarities of 16-75 µm Pr3+ luminescence in Ge36Ga5Se59 glass

High-purity samples of the new Ge36Ga5Se59 glass composition doped with 2×1019, 5×1019 and 1020 cm−3 of Pr3+ atoms were synthesized and their luminescent properties were investigated in the 1.6–7.5 µm spectral range. The luminescence registration method involved has made it possible to separate the spectra of the overlapping transitions in Pr3+ in the 2–2.7 µm emission band and to determine the respective lifetimes as well as their concentration dependencies. High sensitivity of the detection system has allowed to detect weak luminescence band at ∼7.2 µm corresponding to 3F3→3F2 transition for the first time in Pr doped glasses. The experiments showed that intense cross-relaxation processes in investigated glasses can cause a steep ∼ 5 µm emission rise with Pr3+ concentration increase. This effect can be of use for the design of efficient ∼ 5 µm luminescent sources with population efficiency significantly exceeding 100% (when pumped at ∼ 1.5 µm) and luminescence quantum yield close to unity.

Visible to Near‐Infrared Persistent Luminescence and Mechanoluminescence from Pr3+‐Doped LiGa5O8 for Energy Storage and Bioimaging

AbstractHere, a novel multifunctional phosphor of Li1−xGa5O8:xPr3+ is reported. The crystal structure, mechanoluminescence (ML), persistent luminescence (PersL), photoluminescence (PL) and photoluminescence excitation (PLE) are systematically studied. LiGa5O8 emits blue PersL peaked at 437 nm after irradiation by a 254 nm lamp for 10 s, and corresponding PersL can be observed for 30 min by naked eyes. In the same case, the PersL from Li0.995Ga5O8:0.005Pr3+ covers visible to near‐infrared lights (400–1000 nm) which can persist for 120 min. Thermoluminescence analysis shows Pr3+ doping not only increases the shallower trap (0.73 eV) concentration by at least 20 times but also helps the formation of deeper trap centers (0.87 eV). The differences between ML and PersL spectra reveal the selective effects of mechanical stimuli on the transitions of Pr3+ ions. In the end, the fabrication of an intelligent PersL quick response code (QR‐code) permits optical information write‐in after irradiation by a 254 nm lamp and then cryptical information of “SCUT” can be read out by thermal stimulation which shows the potential in information storage. Moreover, the biological tissues penetration experiments and cytotoxicity tests are carried out to display the potential of PersL in bioimaging.

Luminescence enhancement for Y2Mo4O15:Pr3+ red-emitting phosphors by Tb3+ co-doping

A series of Y2Mo4O15:Pr3+, Tb3+ red-emitting phosphors is synthesized via a solid-state reaction. The X-ray diffraction results indicate that the patterns of Y2Mo4O15:Pr3+, Tb3+ samples match well with the standard Y2Mo4O15 monoclinic structure. Under blue excitation at 453 nm, the Y2Mo4O15:Pr3+ phosphors show a red emission peaked at 614 nm, corresponding to the characteristic 1D2 → 3H4 electronic transition of Pr3+. Under near-ultraviolet excitation at 375 nm, the Y2Mo4O15:Tb3+ phosphor results in a double emission at 552 nm and 490 nm, which corresponding to the 5D4 → 7F5 and 5D4 → 7F6 electronic transitions of Tb3+. Furthermore, the luminescence properties of Y2Mo4O15:Pr3+ phosphor, especially luminescence intensity, was observably improved by the Tb3+ co-doping, which due to the emission peak of Tb3+ matches well with the excitation peak of Pr3+ at 490 nm and the resulted energy transfer between Tb3+ and Pr3+. The chromaticity coordinates of Y2Mo4O15:Pr3+, Tb3+ phosphors are all located in the red region. The results indicate that the prepared Y2Mo4O15:Pr3+, Tb3+ red phosphors are suitable for the applications of blue-excited warm white light-emitting diodes.

Spectroscopic investigations of Pr3+ ions doped CNGG and CLNGG single crystals

Spectroscopic characteristics of Pr3+ ions doped CNGG and CLNGG single crystals were investigated in order to assess their potential as laser materials for visible emission. The Judd-Ofelt intensity parameters for the f-f transitions of Pr3+ ions were used to determine spectroscopic and laser emission features. The temperature dependence of the absorption spectra for the 3H4 → 3P0 transition was used to highlight the multicenter structure, different Stark levels, hot bands, and also the connection between the vibronic and electronic lines. The presence of electron-phonon interaction was also observed in the emission spectra corresponding to the 3P0 → 3H4 transition under different excitation wavelengths. Based on low temperature absorption and emission spectra, partial energy level diagrams of Pr3+ ions doped in CNGG and CLNGG single crystals were obtained. The emission cross-sections for different transitions of Pr3+ ions were evaluated by the Fuchtbauer-Ladenburg formula. The fluorescence decay curve of the 1D2 level was measured under selective excitation at different concentrations and temperatures. The concentration quenching process for the 1D2 state was also studied.

Luminescence of Pr3+ Impurity Centers and Defects in Sr9Sc (PO4)7:Pr3+

The spectroscopic characteristics and luminescence decay kinetics of Sr9Sc(PO4)7:Pr3+(1%) were investigated using synchrotron radiation of ultraviolet (UV), vacuum ultraviolet (VUV) and X-ray ranges, as well as pulsed cathodoluminescence (PCL) methods at temperatures of 10, 90, and 295 K. The luminescence spectra contain three groups of bands and lines. In the UV range, the observed bands correspond to interconfigurational 5d → 4f transitions in Pr3+ ions. In the visible spectrum, the wide luminescence band of defects dominates, as well as narrow lines associated with intraconfigurational 4f → 4f transitions in Pr3+ ions. When excited by an electron beam (5 Hz), the main component with a decay time τ ∼ 17 ns dominates in the decay kinetics of the 5d → 4f luminescence. The decay kinetics of 5d → 4f luminescence upon excitation with high-frequency (τ ∼ 8 MHz) synchrotron radiation of the X-ray range contains a fast component (τ ∼ 15 ns) against the background of the slow component of the μs-range. An effective nonradiative energy transfer is observed from impurity centers to defects, as well as from the host to Pr3+ ions and defects.

Luminescence of Pr3+ and Nd3+ Ions in Double Molybdates

The optical spectra of samples of double zirconium molybdates activated by rare-earth Pr3+ and Nd3+ ions are studied. The presence of bands corresponding to the 4f–4f transitions of Pr3+ and Nd3+ trivalent ions in the absorption, excitation, and luminescence spectra is shown. A strong dependence of the luminescence intensity of Pr3+ ions on temperature is revealed.