Preparation,characterization and luminescent properties of spherical CaTiO3:Pr3+ phosphors by spray pyrolysis

In this paper, spherical Pr³⁺-doped CaTiO₃ phosphor particles were fabricated through a two-step spray pyrolysis process, using citric acid and polyethylene glycol (PEG) as additives. X-ray diffraction (XRD), scanning electron microscopy (SEM), High-resolution transmission electron microscopy (HRTEM), thermogravimetric and differential thermal analysis (TG–DTA), X-ray photoelectron spectra (XPS), photoluminescence (PL), cathodoluminescence (CL) spectroscopy, and lifetime measurements were employed to characterize these samples. The results reveal that the as-prepared CaTiO₃:Pr³⁺ phosphors are spherical with submicron particle size. The particles show a strong red emission corresponding to ¹D₂–³H₄ (612 nm) of Pr³⁺ under the ultraviolet excitation (325 nm) and low voltage electron beams (1–5 kV). Furthermore, the morphology, PL and CL intensities of the CaTiO₃:Pr³⁺ phosphors can be tuned by altering the concentration of PEG, annealing temperature, and acceleration voltage. These phosphors show potential applications in the field of field emission displays (FEDs).     

Ab initio theoretical study of luminescence properties of Pr3+-doped Lu2O3

Ab initio embedded cluster calculations have been performed on $\hbox{Pr}^{3+}$ -doped $\hbox{Lu}_2\hbox{O}_3$ , in order to investigate the mechanism responsible for the highly efficient $^3P_0\rightarrow^1D_2$ non-radiative relaxation experimentally observed. $(\hbox{PrO}_6)^{9-}$ embedded clusters representing the C ₂ and S ₆ substitutional sites of Pr³⁺:Lu₂O₃ have been studied using wave function-based methods. It is found that an outward relaxation of the first coordination sphere around the impurity takes place upon doping. At the relaxed geometry of the lowest spin triplet 4f5d state, all the 4f5d states lie much higher in energy than all 4f ² states (except the ¹S multiplet). This result is in opposition to the interpretation of intersystem crossing through a low-lying 4f5d excited state of Pr³⁺ as the mechanism for the fast non-radiative ³ P ₀????¹ D ₂ relaxation proposed in the literature. Absorption to the lowest spin triplet 4f5d state is calculated to be around 4,800?cm^?1 higher for the C ₂ site than for the S ₆ site, supporting the assignment of bands in the excitation spectrum previously reported.     

Review of the synthesis,characterization, and properties of LaAlO3 phosphors

In this review different methods of preparing lanthanum aluminate (LaAlO₃) phosphors are discussed. The molten salt method, the combustion method, the sucrose method, and the coprecipitation technique are the best methods for preparing LaAlO₃ phosphors with small particle size and high surface area by low-temperature synthesis. LaAlO₃ usually has a rhombohedral structure. It has good dielectric properties and, hence, is regarded as an attractive alternative to SiO₂ in microelectronic devices. LaAlO₃ phosphors have excellent chemical and thermal stability, mechanical durability, and exploitable optical and electronic properties, leading to a wide range of potential applications. LaAlO₃ phosphors doped with rare-earth ions have luminescence properties and can, hence, be used in optical display systems.     

Synthesis, characterization and photoluminescence properties of Ce3+-doped ZnO-nanophosphors

The present study involves the synthesis of Ce³⁺ doped ZnO nanophosphors by the zinc nitrate and cerium nitrate co-precipitation method. The synthesized nanophosphors were characterized with respect to their crystal structure, crystal morphology, particle size and photoluminescence (PL) properties using X-ray diffraction (XRD), scanning electron microscopy (SEM)/energy dispersive X-ray (EDX), transmission electron microscopy (TEM)/Energy-dispersive X-ray spectroscopy (EDS) and PL-spectroscopy respectively. XRD results revealed that ZnO nanophosphors are single phase and cubic type structures. Further, PL spectra of ZnO:Ce³⁺ nanophosphors showed green emission because of the charge transfer at single occupied oxygen vacancies with ZnO holes and red emission due to the cerium ion transitions. Intensity and fine structure of the Ce³⁺ luminescence and its temperature dependence are strongly influenced by the doping conditions. The formation of ZnO:Ce³⁺ nanophosphors was confirmed by Fourier transform infrared (FTIR) and XRD spectra.     

Studies on the persistent luminescence of Eu2+ and Dy3+-doped SrAl2O4 phosphors: a review

This review includes research papers on different methods of preparation of Eu²⁺ and Dy³⁺-doped SrAl₂O₄ phosphors and papers reporting luminescence studies of the materials. The methods of preparation were compared and it was concluded that solid state reaction is the best method. Papers on characterization of these phosphors by X-ray diffraction and scanning electron microscopy are also discussed. The review ends with a few important conclusions.     

锌对CaTiO3∶Pr3+发光亮度和余辉时间的影响

研究了Zn的不同掺入量、不同合成温度对CaTiO3∶Pr3+红色光致发光材料结晶、初试亮度和余辉时间的影响.用X射线衍射确定了材料的物相构成, Zn的掺入没有导致Ca2Zn4Ti15O36相的出现.发射光谱的峰值位于613 nm,对应了Pr3+的1D2-3F4跃迁发射,且受Zn掺入量的影响.激发光谱呈宽带,随Zn掺入量的不同而变化明显.同时, Zn的掺入量的增加可以显著降低材料的合成温度.适量的Zn的掺入,在适当的合成温度条件下,获得了具有高的初始亮度、余辉时间达1 h左右的红色长余辉材料.     

Octahedron-dependent near-infrared luminescence in Cr3+-activated phosphors

Searching for broadband near-infrared (NIR) materials with high efficiency and excellent thermal luminescence stability is of great significance because of their widespread spectroscopic applications. Different element substitution can modulate the structure and crystal field of host lattice so as to regulate the luminescent properties. Herein, we report the octahedron-dependent NIR luminescence in Cr³⁺-doped KMP₂O₇ (M = Ga, Sc, In, and Lu) phosphors and investigate the effect of octahedral environment on luminescent properties, aiming to provide guidance for host material selection. The decreased crystal field strength leads to the apparent spectral red shift from 815 to 900 nm for the samples of M = Ga to Lu. The small Stokes shift as well as weak electron–phonon coupling effect decreases the non-radiative transition probability and thus gives rise to the highest emission intensity and excellent thermal stability of Cr³⁺-doped KGaP₂O₇. The optimal sample, KGa_0.89P₂O₇:0.11Cr³⁺, possesses an internal/external quantum efficiency of 55.8%/36.6%, and its integrated emission intensity at 423 K can maintain 68% of that at room temperature. Finally, we investigate the potential applications in non-destructive examination field by manufacturing a NIR phosphor-conversion light-emitting diode device.     

乙二醇辅助水热法制备不同形貌的CaTiO_3/CaTiO_3:Pr微晶

对乙二醇存在下水热法制备CaTiO3微晶的形貌进行了研究。对所得样品用X射线衍射、扫描电子显微镜(SEM)、热重分析及红外光谱(FTIR)进行了表征。结果表明,制备的CaTiO3微晶随着乙二醇和水配比的不同,可以形成立方体、三维十字架形及正十二面体等规整的外形。乙二醇在晶粒表面的配位吸附对这些不同形貌的形成有决定的作用。所得样品粒度分布均匀,基本不团聚。掺杂少量Pr3+离子后对样品的微观形貌基本不影响,在200℃低温水热获得的CaTiO3∶Pr样品就有明显的荧光和长余辉发光性能。样品在900℃煅烧后其外形并不发生变化,也不会团聚,但发光性质得到大幅度提高。     

Thermal study in Eu3+-doped boehmite nanofibers and luminescence properties of the corresponding Eu3+:Al2O3

Eu³⁺-doped boehmite nanofiber materials with different Eu³⁺ concentrations were synthesized without any surfactant, and followed by a series of characterizations. It was found that the boehmite nanofibers became coarser with the increase of Eu³⁺ concentration, which resulted in a gradual decrease of their specific surface areas. Moreover, the thermal stability of the boehmite nanofibers was studied by thermogravimetry–differential scanning calorimetry. All materials showed the phase transition from γ-Al₂O₃ to other forms. Yet the transition temperature was increased with the increase of Eu³⁺ concentration. The Eu³⁺-doped boehmite nanofibers with the maximum Eu³⁺ concentrations showed the best thermal stability. Photoluminescence spectra showed that the 2 mol% of doping concentration of Eu³⁺ ions in Eu³⁺:Al₂O₃ nanofiber was optimum.     

Fluorescence spectra of Tb3+-doped dual lanthanide oxyhalide powder phosphors

This short note presents the chemical preparation and recording of the fluorescence spectra of a new series of Tb³⁺-doped (La, Gd)OF, (La, Gd)OCl, (La, Y)OF and (La, Y)OCl powder phosphors. These phosphors have displayed green colour emission when irradiated with UV light. The measured fluorescence levels have been characterized by determining their stimulated emission cross-sections.     

Temperature dependent luminescence characteristics of Sm3+-doped silicate glass

We report here on the optical characterisation of Sm3+ (5 wt%): SiO2 + Al2O3 + Li2O + Na2O + MgO glass from the measurements of optical absorption spectra (at 300 K), total luminescence spectra (10-300 K) and fluorescence lifetimes (10-300 K) of the prominent emission transitions of the Sm3+ ions. Besides its spectral properties, physical and nonlinearity characterising property parameters have also been computed to understand the optical dispersive power of this glass. By the application of Judd-Ofelt parameters (omega(lambda)) of the measured absorption spectrum, the radiative transition probability factors (A) and stimulated emission cross-section (sigma(p)E) of the observed fluorescent levels have been analysed. Both emission intensity and measured lifetimes of the prominent luminescent transition (4G(5/2) --> 6H(7/2)) concerning Sm3+-glass has been showing a descending trend with the rise in temperature with N2-laser (337.1 nm) as the source of excitation.     

Structure-dependent luminescence properties of Eu3+-doped CsBPO4 (B = Mg,Zn)

Eu³⁺-doped monophosphate CsBPO₄ (B = Mg, Zn) was synthesized by conventional solid state reaction. The crystal phase formations and morphology of the phosphates were analyzed by X-ray powder diffraction (XRD) and scanning electron microscope (SEM) measurements, respectively. The luminescence properties, including the photoluminescence excitation and emission spectra, decay curve (lifetime), the color coordinates and the internal quantum efficiency were investigated. Two Eu³⁺-doped monophosphates display very distinct luminescence properties. CsMgPO₄:Eu³⁺ presents the dominant reddish-orange emission from magnetic dipole transition ⁵D₀ → ⁷F₁ and a long luminescence lifetime. In contrast, CsZnPO₄:Eu³⁺ has a pure red color with the dominant induced electric-dipole transition ⁵D₀ → ⁷F₂ and a fast decay. Different results on the luminescence features of CsBPO₄ (B = Mg, Zn):Eu³⁺ were discussed on the base of crystal structure. Eu³⁺ has structure-dependent transitions due to the special microstructure occupied in a given host.     

Synthesis, characterization, and luminescence properties of a new series of Eu3+-containing macrocycles

The synthesis and structural characterization of a series of neutral Eu(3+)-containing macrocyclic complexes, Eu(4)-Eu(7), are reported. The synthetic pathway herein allows for the size and functionality of the macrocycle to be tailored in one step from a common precursor (N,N' '-bis(p-isothiocyanatobenzylcarbamoylmethyl)diethylenetriamine-N,N'N' '-triacetic acid, (3) in high yield. The macrocyclic ligands 4-7 have within their structure a bis-amide derivative of diethylenetriaminepentaacetic acid (DTPA) functioning as the europium chelate that is bridged through thiourea groups by either a butyl (4), hexyl (5), octyl (6), or m-benzyl (7) linker. The two thiourea groups were designed into the host macrocycle to serve as hydrogen-bond donors to potential guest molecules that may alter the luminescence properties of the parent macrocycle. Characterization of the luminescence of Eu(4)-Eu(7) reveals an antenna effect from the ligand, and the luminescence lifetime data reveals the presence of one coordinated water molecule in aqueous solution.     

YF3:Ln3+ (Ln = Ce, Tb, Pr) submicrospindles: hydrothermal synthesis and luminescence properties

YF(3):Ln(3+) (Ln = Ce, Tb, Pr) microspindles were successfully fabricated by a facile hydrothermal method. X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), lifetimes, photoluminescence (PL) and low-voltage cathodoluminescence (CL) were used to characterize the resulting samples. The lengths and diameters of YF(3):0.02Ce(3+) microspindles are around 760 nm and 230 nm, respectively. Adding dilute acid and trisodium citrate (Cit(3-)) are essential for obtaining YF(3) microspindles. A potential formation mechanism for YF(3) microspindles has been presented. PL spectroscopy investigations show that YF(3):Ce(3+) and YF(3):Tb(3+) microcrystals exhibit the characteristic emission of Ce(3+) 5d → 4f and Tb(3+ 5)D(4)→(7)F(J) (J = 6-3) transitions, respectively. In addition, the energy transfer from Ce(3+) to Tb(3+) was investigated in detail for YF(3):Ce(3+), Tb(3+) microspindles. Under the excitation of electron beams, YF(3):Pr(3+) show quantum cutting emission and YF(3):Ce(3+), Tb(3+) phosphors exhibit more intense green emission than the commercial phosphor ZnO:Zn.     

纳米Y2O3:Eu3+超声辐射沉淀制备及其性能研究

采用超声辐射沉淀法以草酸为沉淀剂制备出纳米Y2O3:Eu^3 粉体。利用XRD、TG-DTA、TEM等手段对其进行了表征．并对其光谱特性进行了研究。结果表明：将超声辐射引入普通沉淀法中,可显著提高粉体性能,所得纳米Y2O3:Eu^3 为球形,粒度分布均匀,粒径约为38～45nm,与微米晶相比,该纳米晶的发射光谱发生蓝移,激发光谱发生红移。     

Synthesis, characterization and luminescence properties of SrLa2(MoO4)4:Eu phosphors

SrLa₂(MoO₄)₄ (SLM) phosphors doped with Eu³⁺ ions were prepared by a sol–gel combustion method using citric acid as a fuel/reductant and nitrates as oxidants. The crystallization processes were tracked by means of X-ray diffraction and thermo-gravimetric analysis and differential scanning calorimetry. The size and shape of the products were characterized using a scanning electron microscope, while the luminescent spectra of these resulting phosphors were recorded using a photoluminescence (PL) spectrophotometer. PL studies reveal that the emission intensity of SLM:Eu phosphors was strongly related to sintering temperature as well as the doping concentration of Eu³⁺ ions. The present phosphor has a strong excitation at 395 and 459 nm, indicating that it could serve as a promising red-emitting candidate for near-UV and GaN-based blue light-emitting diode chips.     

水热法制备长余辉发光材料CaTiO3:Pr,Al及其发光性能

以氯化钙、四氯化钛和Pr6O11为原料,采用水热法结合煅烧制备了掺镨的钛酸钙长余辉发光材料.水热产物进行了XRD、扫描电镜、荧光光谱等表征.研究了水热条件、煅烧条件以及添加Al3+(以Al(NO3)3为原料)对CaTiO3:Pr粉末发光的影响.结果表明:直接水热即可得到具有一定余辉的CaTiO3:Pr发光材料,添加Al3+后长余辉性能显著提高.在200℃水热反应6 h可获得性能最佳的产物,最佳煅烧条件为900℃煅烧1 h.     

Eu3+- and Ho3+-doped Ba3Al2O6- and MgAl2O4-type phosphors and their photoluminescent properties

Journal of Thermal Analysis and Calorimetry - The aluminate hosts were basically activated with the Eu3+- and Ho3+-ions which were prepared by solid-state reaction in this study. The DTA/TG results...     

Physical,structural and luminescence investigation of Eu3+-doped lithium-gadolinium bismuth-borate glasses for LEDs

The aim of the current report is to fabricate Eu³⁺-doped glasses with the chemical composition of 50Li₂O-15Gd₂O₃-5Bi₂O₃-(30-x)B₂O₃-xEu₂O₃ (where x = 0.5, 1.0, 1.5, 2.0 and 2.5 mol%), with the help of conventional melt quenching technique. The fabricated glasses have been studied with help of physical, structural and luminescence properties for application of LEDs. The structural properties were investigated by XRD and FTIR spectra. Physical properties have been measured. Direct and indirect optical energy band gap (E_g) have been calculated and found to be increasing with Eu₂O₃ concentration. Luminescence spectra have been observed from photo and radioluminescence spectra and found in good agreement with each other, however the concentration quenching was not determined for the samples. The high-covalence and asymmetric nature was confirmed from Photoluminescence emission and RL emission transition as well as from the higher values of luminescence intensity ratio. The JO parameters have been found for the better performance of lasing materials. The lifetime's data have been found to be decreasing from 1.64 to 1.50 ms, which is the confirmation of energy transfer in Eu³⁺ ions through cross relaxations. From the calculated properties it has been suggested that the present glass samples might be good for red-light emitting devices.