Green synthesis,structural and luminescent characterization of BaZrO3:Eu3+ nanoparticles

This paper presents experimental results of the structural, morphological, and luminescence characterization of Eu³⁺ doped BaZrO₃ powders produced by the green synthesis method. The highly crystalized cubic structure perovskite powders of the formula BaZrO₃ were synthesized by the chemical hydrothermal method. The phase of the compound and the average particle size were determined using X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Powder samples were characterized also by photoluminescence (PL) and thermoluminescence (TL) techniques. Results showed that BaZrO₃ crystallizes in its perovskite cubic phase, with a crystal size circa 40 nm. The presence of each element of the compound was confirmed by the energy disperse spectroscopy (EDS) technique. The PL emission spectra, at room temperature, were obtained using 395 nm as excitation wavelength. The spectra showed the characteristic emissions of Eu³⁺ ion. The intensity of the PL emission spectra varies with the Eu³⁺ concentration and shows a maximum luminescence efficiency when the synthesis of BaZrO₃ was performed using a content of 5 mol% Eu³?. The thermoluminescence data shows that at the heating rate of 10 °C/s, BaZrO₃:Eu³⁺ doped with 5% of dopant concentration exhibits two TL peaks: first of them rapidly decaying peaks at about 110 °C and a high sensitivity peak at 235 °C TL. The correlation between luminescence intensity and concentration quenching of the prepared phosphor was investigated. Present findings substantiate the ability of the BaZrO₃ nanopowder sample to be a promising candidate for luminescence applications.     

Highly sensitive optical thermometer of Sm3+, Mn4+ activated LaGaO3 phosphor for the regulated thermal behavior

Sm³⁺, Mn⁴⁺ co-activated LaGaO₃ phosphors, giving the characteristic emissions of orange and red emission simultaneously, were prepared by a solid-state reaction. Their luminescence properties, energy transfer behavior, thermal stability, and ratiometric temperature sensing performance were investigated. Thanks to the inhibition of energy transfer between Sm³⁺ and Mn⁴⁺ ions at high temperature and the reconstruction of the traps, the distinct optical behavior of the involved activators dependent on the ambient temperature was evaluated. Anti-thermal quenching performance of Sm³⁺ ions along with the emission declination of Mn⁴⁺ ions was observed. Hence, the optical thermometry characteristics of the resultant phosphor based on the fluorescent intensity ratio (orange/red) realize a recorded temperature sensitivity of 4.19% K⁻¹ and 2.09% K⁻¹. Moreover, the as-explored film combined with the LaGaO₃: Sm³⁺, Mn⁴⁺ phosphor is demonstrated to be a promising multi-color optical thermometer.     

Photoluminescence and electron-beam excitation induced cathodoluminescence properties of novel green-emitting Ba4La6O(SiO4)6:Tb3+phosphors

Tb³⁺ions activated Ba₄La₆O(SiO₄)₆ (BLSO:Tb³⁺) phosphors were synthesized by a citrate sol-gel method. The X-ray diffraction pattern confirmed their oxyapatite structure. The field-emission scanning electron microscope image established that the BLSO:Tb³⁺phosphor particles were closely-packed and acquired irregular shapes. The photoluminescence (PL) excitation spectra of BLSO:Tb³⁺phosphors showed intense f–d transitions along with low intense peaks corresponding to the f–f transitions of Tb³⁺ions in the lower energy region. The PL emission spectra displayed the characteristic emission bands of Tb³⁺ions, and the optimized concentrations were found to be at 1 and 6 mol% for blue and green emission peaks, respectively. The cathodoluminescece (CL) spectra exhibited a similar behavior that was observed in the PL spectra except the intensity variations in the blue and green regions. The CL spectra of the BLSO:6 mol% Tb³⁺phosphor unveiled accelerating voltage induced luminescent properties.     

Down-conversion from Er3+-Yb3+ codoped CaMoO4 phosphor: A spectral conversion to improve solar cell efficiency

The present paper focuses on near infrared (NIR) down-conversion photoluminescence (PL) properties by studying the energy transfer mechanism between Er³⁺ and Yb³⁺ in CaMoO₄:Er³⁺, Yb³⁺ phosphors. We have successfully synthesized a series of Er³⁺ doped and Yb³⁺ codoped CaMoO₄ phosphors by hydrothermal method. The down-conversion of Er³⁺-Yb³⁺ combination with CaMoO₄ phosphor is designed to overcome the energy losses due to spectral mismatch when a high energy photon is incident on the Si-solar cell. The XRD, FESEM, EDX, PL, UV–Vis, Lifetime measurements were carried out to characterize the prepared down-converting phosphors. The crystallinity and surface morphology were studied by X-ray diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM) techniques. The down-conversion PL spectra have been studied using 380 nm excitation wavelength. The Er³⁺ doped phosphors exhibit hypersensitive emission at 555 nm in the visible region due to ⁴S_3/2→⁴I_15/2 transition. The addition of Yb³⁺ into Er³⁺ doped CaMoO₄ attribute an emission at 980 nm due to ²F_5/2→²F_7/2 transition. The decrease in emission intensity in visible region and increase in NIR region reveals the energy transfer from Er³⁺ to Yb³⁺ through cross relaxation. The UV–Vis–NIR spectra shows the strong absorption peak around 1000 nm due to Yb³⁺ ion. The lifetime measurement also reveals the energy transfer from Er³⁺ to Yb³⁺ ions. The maximum value of energy transfer efficiency (ETE) and corresponding theoretical internal quantum efficiency are estimated as 74% and 174% respectively.     

A Novel Blue‐Emitting Phosphor of Eu2+‐Activated Magnesium Haloborate Mg3B7O13Cl

Eu²⁺‐doped magnesium haloborate Mg₃B₇O₁₃Cl was synthesized by the conventional high‐temperature solid‐state reaction. The phase formation was confirmed by X‐ray powder diffraction (XRD) measurements and structure refinement. The photoluminescence excitation and emission spectra, and decay curves were measured. Under the excitation of near‐UV light, Eu²⁺‐doped Mg₃B₇O₁₃Cl presents a narrow blue‐emitting band centered at 423 nm. The maximum absolute quantum efficiency (QE) of Mg₃B₇O₁₃Cl:Eu²⁺ phosphor was measured to be 80% excited at 385 nm light at 300 K. The thermal stability of the blue luminescence was evaluated by the luminescence decays as a function of temperature. The phosphor shows an excellent thermal stability on temperature quenching effects. Moreover, Mg₃B₇O₁₃Cl:Eu²⁺ phosphor shows scintillation characteristics excited by X‐ray irradiation at room temperature and presents a blue luminescence band with a fast lifetime of 600 ns.     

Analysis of structural,optical and magnetic properties of Fe/Co co-doped ZnO nanocrystals

In this paper, the structural, optical and magnetic properties of pure ZnO and Fe/Co co-doped ZnO nanoparticles are presented. Rietveld refinement of XRD pattern revealed the single phase wurtzite structure for prepared samples. FTIR study confirmed the formation of tetrahedral coordination between zinc and oxygen ions. SEM and TEM techniques were used to examine the morphology of samples. The absorption spectra showed the decrease in optical energy band gap with Fe/Co co-doping in ZnO. PL spectra demonstrated five peaks correspond to the ultraviolet region, violet, violet-blue, blue-green and green in the visible region. Emission peak in the UV region is attributed to near band-edge excitonic emission. Other four emission peaks in PL spectra are related to different defect states. M-H curve showed room temperature ferromagnetic (RTFM) behaviour of doped ZnO sample. This paper enhances the understanding of structural, optical and magnetic properties of Fe/Co co-doped ZnO nanocrystals for application in spintronics, solar cells, and ceramics.     

Synthesis and luminescent properties of Sr4−xSi3O8Cl4: xEu3+ red phosphor by hydrothermal method

Sr_4‐xSi₃O₈Cl₄:xEu³⁺ (SSOC:Eu³⁺) phosphors were successfully synthesized by hydrothermal method. The crystallization of this phosphor was analyzed by means of X‐ray diffraction patterns. The size and morphology were recorded using SEM patterns of samples. And the PLE and PL spectra were characterized by a PL spectrophotometer. Excited by 394 nm UV light, the intense red emission is recognized in SSOC:Eu³⁺ phosphor and the main emission peak located at 620 nm. The influences of Eu³⁺ concentration, pH value of reaction solution, and charge compensator on PL spectra of SSOC:Eu³⁺ phosphors were investigated. The results revealed that this red phosphor had potential applications for white LEDs.     

Mg3Y2Ge3O12:Bi3+ UV fluorescent phosphor as the TiO2 “sensitizer” for enhancing the heavy oil viscosity reduction

Nowadays, visible fluorescent materials based on rare earth (RE) and non-RE ions doping have been extensively explored for white LEDs. As for the UV fluorescent materials, it is well known that they are not suitable for the lighting applications. As a result, when compared to the visible fluorescent materials, previous works paid little attention to the UV fluorescent materials. In this work, we report a type of Mg₃Y₂Ge₃O₁₂:Bi³⁺ UV fluorescent phosphor. To understand the crystal structural information and photoluminescence (PL) properties of samples, we have used the X-ray diffraction (XRD), scanning electronic microscope (SEM), UV–visible diffuse reflectance and PL spectra to characterize them. The structural results reveal that the Bi³⁺ doped sample show their particle size at about 30 μm. The PL results show that the Bi³⁺ doped sample upon excitation at 230 nm can show a broad emission band that can almost cover the whole UV spectral region from 290 nm to 410 nm. Since this UV fluorescent band is exactly in agreement with the UV absorption region of TiO₂ semiconductor, we have fabricated several Mg₃Y₂Ge₃O₁₂:Bi³⁺/TiO₂-based ceramic plates and proposed used them to serve as an efficient UV irradiation source for photocatalytic application. As a result, we find that the TiO₂ can exhibit the significantly enhanced photocatalytic property for the heavy oil viscosity reduction after adding the Mg₃Y₂Ge₃O₁₂:Bi³⁺ UV fluorescent phosphor.     

Dual-mode optical thermometry based on Bi3+/Eu3+ co-activated BaGd2O4 phosphor with high sensitivity and signal discriminability

A series of BaGd₂O₄:Bi³⁺,Eu³⁺ phosphors with dual-emitting centers were prepared by high-temperature solid-state method. X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), fluorescence spectroscopy, lifetime decay curve and variable temperature emission spectroscopy were used to systematically study the structure, luminescence performance and temperature characteristics. Under ultraviolet (UV) excitation, the BaGd₂O₄:Bi³⁺,Eu³⁺ phosphor showed a broad-band emission in the blue region corresponding to transitions of Bi³⁺ ions and the sharp red light emission corresponding to Eu³⁺ ions. The Bi³⁺ and Eu³⁺ ion emission peaks were well-separated, which meets a prerequisite for efficient temperature signal resolution measurement. The fluorescence intensity ratio (FIR) technique was used to measure the different temperature response characteristics between Bi³⁺ blue emission and Eu³⁺ red emission. When the temperature varies from 293 K to 473 K, the relative temperature sensitivity (S_r) of BaGd₂O₄:Bi³⁺,Eu³⁺ phosphors is obtained, was determined as 1.0182%K⁻¹. In addition to calculating the relative sensitivity by FIR technology, we can also obtain the value of S_r through experiments and formulas related to the decay life, and found to be 1.0651%K⁻¹. Therefore, BaGd₂O₄: Bi³⁺,Eu³⁺ phosphor is an excellent non-contact optical temperature measurement material.     

A benign approach for novel synthesis of Eu3+ doped MgNb2O6: Its photoluminescence and photocatalytic studies

The Present work involves the production of Eu³⁺ (1–11 mol %) doped MgNb₂O₆ nanophosphors (NPs) by combustion technique using ODH as a fuel for the first time and well characterized. The average crystallite and the energy gap of the samples were found to be in the range of 20–45 nm and 4.65–5.66 eV respectively, TEM results reflects the same crystallite size values. The effect of doping was confirmed by the characteristic emission peaks recorded at ~535, 590, 614, 642 and 698 nm may be attributed to the 4f–4f intra shell transitions (⁵D₀→⁷F_j=0,1,2,3,4) of Eu³⁺ cations when bombarded at 395 nm energy. Judd–Ofelt parameters (Ω₂, Ω₄), transition probabilities (A_T), quantum efficiency (η), luminescence lifetime (τ_rad) are discussed in detail. From the emission spectra, CIE (Commission International de I’ Eclairage) chromaticity co-ordinates and Correlated color temperature (CCT) were estimated. Langmuir-Hinshelwood model was used to study the photocatalytic degradation of AR-88 dye. The above results confirmed that the present phosphor can be potentially used for display and photocatalytic applications.     

Luminescence Properties of Dual‐Emission (UV/Visible) Long Afterglow Phosphor SrZrO3: Pr3+

A dual‐emission (UV/Visible) phosphor SrZrO₃: Pr³⁺ was prepared by a high‐temperature solid‐state reaction method. The afterglow including ultraviolet (UV) and visible region which originated from self‐trapped excitons and f–f transitions in Pr³⁺ was first observed after the short UV‐irradiation. All as‐prepared phosphors were studied systematically by X‐ray diffraction, photoluminescence (PL) spectra, decay curves, long afterglow spectra (LAG), and thermoluminescence (TL) glow curves. The PL intensity and the performance of afterglow are dependent on the concentration of Pr³⁺ ions. The optimal concentration of Pr³⁺ ions for the brightest PL emission and the best afterglow characteristic were experimentally to be 0.5% and 0.4%, respectively. The different mechanisms for concentration quenching in both cases were discussed. A model was proposed on the basis of experimental results to discuss the mechanism of LAG in SrZrO₃: Pr³⁺ in detail.     

Microstructure and optical properties of Pr3+-doped hafnium silicate films

In this study, we report on the evolution of the microstructure and photoluminescence properties of Pr³⁺-doped hafnium silicate thin films as a function of annealing temperature (T_A). The composition and microstructure of the films were characterized by means of Rutherford backscattering spectrometry, spectroscopic ellipsometry, Fourier transform infrared absorption, and X-ray diffraction, while the emission properties have been studied by means of photoluminescence (PL) and PL excitation (PLE) spectroscopies. It was observed that a post-annealing treatment favors the phase separation in hafnium silicate matrix being more evident at 950°C. The HfO₂ phase demonstrates a pronounced crystallization in tetragonal phase upon 950°C annealing. Pr³⁺ emission appeared at T_A = 950°C, and the highest efficiency of Pr³⁺ ion emission was detected upon a thermal treatment at 1,000°C. Analysis of the PLE spectra reveals an efficient energy transfer from matrix defects towards Pr³⁺ ions. It is considered that oxygen vacancies act as effective Pr³⁺ sensitizer. Finally, a PL study of undoped HfO₂ and HfSiO_x matrices is performed to evidence the energy transfer.     

Investigation of Eu2+ luminescence in barium tetraphosphate Ba3P4O13 polycrystalline ceramics

In this paper, Ba₃P₄O₁₃:Eu²⁺ phosphor was synthesized by a solid-state reaction. The photoluminescence (PL) emission spectrum and luminescence decay kinetics confirm that the doped Eu²⁺ ions can occupy two different Ba²⁺ sites. The PL excitation spectrum shows a broad band matching well with the emission of near-UV chip. Ba₃P₄O₁₃:Eu²⁺ is a promising phosphor for near-UV chip excited white LEDs. The doped Eu³⁺ ions can also be reduced to Eu²⁺ ions in air atmosphere at high temperature. Charge compensation mechanism is applied to explain this kind of abnormal reduction.     

Structure and Luminescence Characteristics of Eu3+‐Activated Trigonal Layered Perovskite Ba2La2ZnW2O12

Eu³⁺‐doped tungstate Ba₂La₂ZnW₂O₁₂ phosphors with perovskite‐structure were prepared by the high temperature solid‐state reaction. The X‐ray powder diffraction (XRD) patterns and structure refinements indicate that the phosphors crystalized in the trigonal layer‐perovskite. The luminescence properties of the phosphors were investigated such as photoluminescence (PL) excitation and emission spectra, decay lifetimes, and color coordinates. It was found that the pure host shows self‐activated emission excited by the UV light. Moreover, Ba₂La₂ZnW₂O₁₂ also shows scintillation characteristics under the X‐ray irradiation. The near‐UV and blue light can efficiently excite Eu³⁺‐doped Ba₂La₂ZnW₂O₁₂ phosphors inducing the strong orange–red luminescence. The optimal Eu³⁺ doping concentration in this host is 40 mol%. The luminescence spectra and the luminescence color of the phosphors strongly depend on the doping levels and excitation wavelength. The different luminescence features were discussed on the base of crystal structure. Eu³⁺ ions have two possible substitutions on A or B sites in this trigonal layered perovskite. The phosphor could act as a candidate for the potential application in near‐UV excited white‐LEDs lighting.     

The photoluminescence characteristics of Tb2S3 nanoparticles embedded in sol–gel silica xerogel

The silica xerogel doped with Tb₂S₃ nanocrystallites has been prepared by sol–gel process. UV–Vis spectra, transmission electron micrograph (TEM), excitation spectra and photoluminescence (PL) spectra of doped xerogel samples have all been investigated at room temperature. A novel luminescent phenomenon has been observed from Tb₂S₃ nanoparticles doped silica xerogel. The emission spectrum of the doped sample shows high fluorescence intensity. The photoluminescence spectrum of the doped samples consists of two emission bands, one at 440 nm and the other at 600 nm. The sharp emission band of Tb₂S₃ from the doped samples has been assigned to the luminescence centers of Tb₂S₃ quantum dots in the porous phosphorescence silica xerogel.     

Luminescence and structural properties of Gd2SiO5:Eu3+ phosphors synthesized from the modified solid state method

This paper reports the preparation of Eu³⁺ doped Gadolinium oxyorthosilicate (Gd₂SiO₅:Eu³⁺) phosphor with different concentration of Eu³⁺(0.1–2.5 mol%) using the modified solid state reaction method. The synthesis procedure of the Gd₂SiO₅:Eu³⁺phosphor using inorganic materials such as Gd₂O₃, silicon dioxide (SiO₂), europium oxide (Eu₂O₃) and boric acid (H₃BO₃) as flux is discussed in detail. The prepared phosphor samples were characterized by using X-Ray Diffraction (XRD), Field Emission Gun Scanning Electron Microscopy (FEGSEM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), Photoluminescence (PL) and Thermoluminescence (TL). The Commission Internationale de l′Eclairage(CIE) coordinates were also calculated. The PL emission was observed in the 350–630 nm range for the Gd₂SiO₅:Eu³⁺ phosphor. PL excitation peaks were observed at 266, 275, 312 and 395 nm while the emission peaks were observed at 380, 416, 437, 545, 579, 589, 607, 615 and 628 nm. The emission peak at 615 nm was the most intense peak for all the different Eu³⁺ concentration samples. From the XRD data, using the Scherrer's formula, the average crystallite size of the Gd₂SiO₅:Eu³⁺ phosphor was calculated to be 33 nm. TL was carried out for the phosphor after both UV and gamma irradiation. The TL response of the Gd₂SiO₅:Eu³⁺ phosphor for the two different radiations was compared and studied in detail. It was found that the present phosphor can acts as a single host for red emission (1.5 mol%) for display devices and light emitting diode (LED) and white light emission for Eu³⁺(0.1 mol%) and it might be used as a TL dosimetric material for gamma dose detection.     

Investigation of luminescence properties of Pb2+‐doped Sr2B2O5 phosphor

A near‐UV emitting phosphor, Pb²⁺‐doped Sr₂B₂O₅ was synthesized by the solid‐state reaction method at 900°C for 3 hours in air. The structure of the phosphor was verified by X‐ray diffraction study which shows monoclinic phase. Fourier transform infrared (FTIR) analysis confirmed the formation of Sr₂B₂O₅. The excitation and emission spectra of the synthesized phosphors were investigated at room temperature with photoluminescence spectrophotometer. The emission and excitation bands of Pb²⁺‐doped Sr₂B₂O₅ were observed at 370 and 289 nm, respectively. The dependence of the PL intensities on the Pb²⁺ concentration for the Sr_2?xPb_xB₂O₅ (0.01 ≤ x ≤ 0.03) phosphors was studied and it was observed that the concentration quenching of Pb²⁺ in Sr₂B₂O₅ is 0.025 mol.     

Spectroscopic and photoluminescence characteristics of Sm3+ doped calcium aluminozincate phosphor for applications in w-LED

Monophase Calcium Aluminozincate (Ca₃Al₄ZnO₁₀) phosphor doped with Sm³⁺ ions by varying concentrations have been prepared at 1300 °C using conventional solid state reaction technique. The crystal structure and phase analysis of the as-prepared phosphor has been carried out by X-ray Diffraction (XRD) studies. Morphology and functional groups present in the phosphor have been investigated thoroughly by using Scanning Electron Microscope (SEM) and Fourier Transform Infrared (FT-IR) spectral measurements, respectively. Under 401 nm excitation, the as-prepared phosphor exhibit intense visible orange emission at 601 nm. It has been observed that 1.0 mol% of Sm³⁺ ions concentration is optimum to give intense visible orange emission. The PL analysis reveals that the dipole-dipole interaction is primarily responsible for the concentration quenching observed beyond 1.0 mol% of Sm³⁺ ions. The TR-PL study reveals a bi-exponential behavior of decay curves with an average lifetime of the order of microseconds. The CIE coordinates (x=0.574 and y=0.424) measured for the optimized phosphor are very close to the intense orange emission coordinates specified by Nichia Corporation developed Amber LED NSPAR 70BS (0.570, 0.420). The spectroscopic, PL and TR-PL studies suggest the potential use of Sm³⁺ doped calcium aluminozincate phosphors for display and white light emitting devices.     

Expanded and Enhanced Deep‐UV Excitations of Mn2+‐Doped Phosphate Glasses Sensitized by Gd3+ Ions

Mn²⁺‐doped phosphate glasses sensitized by Gd³⁺ ions are investigated. Enhanced photoluminescence (PL) properties of the samples are found with the excitations expanding toward the deep‐UV part of the spectrum. PL emission and excitation spectra correlated with the lifetime data consistently present evidences of the enhanced Mn²⁺ emission in association with the energy transfer from Gd³⁺ ions. In particular, the Gd³⁺ codoping benefits greatly the energy harvesting of Mn²⁺ ions, resulting in the enhanced and tunable excitations of Mn²⁺ ions which expand toward the deep‐UV part of the spectrum at 273 and 311 nm, respectively. Thus by Gd³⁺ sensitizing, the excitation source of the Mn²⁺ emission has covered the broad range of the spectrum from the original blue and near‐UVA to the deep‐UVB and UVC together with the enhanced emission in the green‐to‐red spectral region. The possible energy‐transfer mechanisms involved are discussed.     

Synthesis,structural characterization,and photoluminescence properties of Eu3+‐doped Mg3‐xEux(BO3)2 phosphor

Eu³⁺‐doped Mg_3‐xEu_x(BO₃)₂ (x = 0.000, 0.005, 0.010, 0.020, 0.050, and 0.100) phosphors were synthesized for the first time by solution combustion synthesis method, which is a fast synthesis method for obtaining nano‐sized borate powders. The optimization of the synthesis conditions of phosphor materials was performed by TG/DTA method. These phosphors were characterized by XRD, FTIR, SEM‐EDX, and photoluminescence, PL analysis. The XRD analysis exhibited that all of the prepared ceramic compounds have been crystallized in orthorhombic structure with space group Pnnm. Also, the influence of europium dopant ions on unit cell parameters of host material was analyzed using Jana2006 program and the crystalline size was determined by Debye‐Scherrer's formula. The luminescence properties of all Eu³⁺‐doped samples were investigated by excitation and emission spectra. The excitation spectra of Mg_3‐xEu_x(BO₃)₂ phosphors show characteristic peak at 420 nm in addition to other characteristic peaks of Eu³⁺ under emission at 613 nm. The emission spectra of Eu³⁺‐doped samples indicated most intensive red emission band dominated at 630 nm belonging to ⁵D₀→⁷F₂ magnetic dipole transition. Furthermore, the optimum or quenching concentration of Eu³⁺ ion has been determined as x = 0.010 showed the maximum emission intensity when it was excited at 394 nm.