Controlled synthesis and luminescent properties of Eu(Eu), Dy-doped Sr3Al2O6 phosphors by hydrothermal treatment and postannealing approach

In this work, Sr₃Al₂O₆: Eu²⁺ (Eu³⁺), Dy³⁺ phosphors have been prepared by hydrothermal treatment and subsequently postannealing approach, using Sr(NO₃)₂, Al(NO₃)₃·9H₂O, and CO(NH₂)₂ as starting materials. The as-obtained phosphors were characterized by means of XRPD, FESEM, and PL techniques. In addition, many reaction parameters were studied in detail, including the initial mole ratios, hydrothermal reaction temperature, calcination temperature and calcination atmosphere. Remarkably, two scientific merits exist herein: Sr₃Al₂O₆: Eu²⁺ (Eu³⁺), Dy³⁺ phosphors can be selectively obtained in a reducing atmosphere (H₂/Ar, 20%+80%) and in air, respectively; adding certain amount of sodium citrate can alter the shape and size of Sr₃Al₂O₆: Eu²⁺ (Eu³⁺), Dy³⁺ phosphors in essence. Besides, the luminescent properties of Sr₃Al₂O₆: Eu²⁺ (Eu³⁺), Dy³⁺ phosphors were studied by excitation spectra, emission spectra and decay curves.     

The effect of calcium substitution on the afterglow of Eu2+/Dy3+ doped Sr4Al14O25

The effect of calcium substitution on the afterglow of tetrastrontium aluminate phosphors (Sr₄Al₁₄O₂₅:Eu²⁺, Dy³⁺) was investigated. A series of (Sr₁-_xCa_x)O⊎nAl₂O₃:Eu²⁺(1%), Dy³⁺(0.5%), with variation of calcium content (x = 0 − 1), were synthesized by a high temperature solid state reaction in a reducing atmosphere. The photoluminescence, persistent luminescence (afterglow), and lumen equivalents of these materials were studied and compared. It turned out that the afterglow properties of the phosphors were strongly dependent on the Sr/Ca ratio. As the Ca content increased, a phase transition and blue shift in emission spectra were observed.      

Synthesis,Persistent Luminescence,and Thermoluminescence Properties of Yellow Sr3SiO5:Eu2+,RE3+ (RE=Ce,Nd, Dy,Ho, Er,Tm, Yb) and Orange‐Red Sr3−xBaxSiO5:Eu2+, Dy3+ Phosphor

Sunlight‐excitable orange or red persistent oxide phosphors with excellent performance are still in great need. Herein, an intense orange‐red Sr_3?xBa_xSiO₅:Eu²⁺,Dy³⁺ persistent luminescence phosphor was successfully developed by a two‐step design strategy. The XRD patterns, photoluminescence excitation and emission spectra, and the thermoluminescence spectra were investigated in detail. By adding non‐equivalent trivalent rare earth co‐dopants to introduce foreign trapping centers, the persistent luminescence performance of Eu²⁺ in Sr₃SiO₅ was significantly modified. The yellow persistent emission intensity of Eu²⁺ was greatly enhanced by a factor of 4.5 in Sr₃SiO₅:Eu²⁺,Nd³⁺ compared with the previously reported Sr₃SiO₅:Eu²⁺, Dy³⁺. Furthermore, Sr ions were replaced with equivalent Ba to give Sr_3?xBa_xSiO₅:Eu²⁺,Dy³⁺ phosphor, which shows yellow‐to‐orange‐red tunable persistent emissions from λ=570 to 591 nm as x is increased from 0 to 0.6. Additionally, the persistent emission intensity of Eu²⁺ is significantly improved by a factor of 2.7 in Sr_3?xBa_xSiO₅:Eu²⁺,Dy³⁺ (x=0.2) compared with Sr₃SiO₅:Eu²⁺,Dy³⁺. A possible mechanism for enhanced and tunable persistent luminescence behavior of Eu²⁺ in Sr_3?xBa_xSiO₅:Eu²⁺,RE³⁺ (RE=rare earth) is also proposed and discussed.     

Tunable luminescence and energy transfer process between Tb3+ and Eu3+ in GYAG:Bi3+, Tb3+, Eu3+ phosphors

A series of Eu³⁺ ions co-doped (Gd_0.9Y_0.1)₃Al₅O₁₂:Bi³⁺, Tb³⁺ (GYAG) phosphors have been synthesized by means of solvothermal reaction method. The XRD pattern of GYAG phosphor sintered at 1500 °C confirms their garnet phase. The luminescence properties of these phosphors have been explored by analyzing their excitation and emission spectra along with their decay curves. The excitation spectra of the GYAG:Bi³⁺, Tb³⁺, Eu³⁺ phosphors consists of broad bands in the shorter wavelength region due to 4f⁸ → 4f⁷5d¹ transition of Tb³⁺ ions overlapped with 6s² → 6s¹6p¹ (¹S₀ → ³P₁) transition of Bi³⁺ ions and the charge transfer band of Eu³⁺–O^2?. The present phosphors exhibit green and red colors due to ⁵D₄ → ⁷F₅ transition of Tb³⁺ ions and ⁵D₀ → ⁷F₁ transition of Eu³⁺ ions, respectively. The emission was shifted from green to red color by co-doping with Eu³⁺ ions, which indicate that the energy transfer probability from Tb³⁺ to Eu³⁺ ions are dependent strongly on the concentration of Eu³⁺ ions.     

Synthesis and characterization of Eu3+/Dy3+ codoped composite phosphors SrAl2Si2O8/SrAlSi1/2O7/2 via a one-pot nitrate-gel process

Composite phosphors SrAl₂Si₂O₈/SrAlSi_1/2O_7/2 codoped with Eu³⁺ and Dy³⁺ were synthesized via a simple one-pot nitrate-gel process. The thermal decomposition process of the precursor is investigated by thermal analysis, X-ray diffraction and infrared spectroscopy, respectively. The as-prepared Eu³⁺/Dy³⁺ codoped SrAl₂Si₂O₈/SrAlSi_1/2O_7/2 phosphors could yield blue (436 nm), bluegreen (486 nm), yellow (583 nm), and red (617 nm) lights under near-UV 380 nm excitation from a composite matrix produced by spontaneous phase separation during heat treatment of the precursor. Moreover, the effects of Dy³⁺ doping concentration on the structures, defect features, and luminescence properties of the composite phosphors were examined in detail.     

Synthesis and optical studies of novel Eu2+ and Ce3+ doped BaMg8Al18Si18O72 phosphors

Novel Eu²⁺ and Ce³⁺ activated BaMg₈Al₁₈Si₁₈O₇₂ phosphors was prepared by combustion method and their PL characteristics were investigated. The result shows that all samples can be excited efficiently by near UV excitation under 334 nm and 316 nm. The emission was observed for BaMg₈Al₁₈Si₁₈O₇₂:Eu²⁺ phosphor at 437 nm corresponding to d → f transition, under 334 nm broad-band excitation, whereas BaMg₈Al₁₈Si₁₈O₇₂:Ce³⁺ phosphor shows emission band at 376 nm under 316 nm excitation. Phase purity of the phosphor was checked with the help of XRD pattern. SEM analysis shows the external morphology of the combustion synthesized phosphor.     

Preparation and characterization of Li0.25Sr0.5(MoO4):Eu 0.253+ red-emitting phosphors for white LEDs by organic gel-thermal decomposition process

Li_0.25Sr_0.5(MoO₄):Eu_0.25³⁺ red-emitting phosphors were prepared by the organic gel-thermal decomposition process with metal salts and citric acid as starting reagents. X-ray diffraction, scanning electron microscopy and photoluminescent spectroscopy were used to characterize the as-prepared phosphors. The Li_0.25Sr_0.5(MoO₄):Eu_0.25³⁺ phase consisting of nanosized crystallites is formed at 400 °C and the nanosized crystallites with a tetragonal-dipyramid morphology increase with the calcination temperature and time. During the early period at 650 °C, the microstructure of the Li_0.25Sr_0.5(MoO₄):Eu_0.25³⁺ crystallites are unstable and the re-crystallization for some particles takes place with a particle morphological modification. The optimized calcination conditions for the Li_0.25Sr_0.5(MoO₄):Eu_0.25³⁺ phosphors are 650 °C for 13 h. The Li_0.25Sr_0.5(MoO₄):Eu_0.25³⁺ phosphors with particle sizes about 0.5 to 2.0 μm obtained under the optimized conditions can be excited by the ultraviolet light 395 nm and blue light 466 nm, which are well met with the requirements for the current commercial near-UV and blue LEDs, and exhibit a high emission performance.     

Facile ion-exchange synthesis of Gd-doped K2Ta2O6 photocatalysts with enhanced visible light activity

One of the well-known ways of increasing the visible light absorption capability of semiconducting materials is cation doping. This study aims to use Gd doping to tailor the bandgap energy of K₂Ta₂O₆ (KTO) for photocatalytic degradation of organic pollutants under visible light irradiation. Accordingly, the parent KTO and Gd-doped KTO with different Gd concentrations (K_2-3xGd_xTa₂O₆; x = 0.025, 0.05, 0.075 and 0.1 mol%) were synthesized by hydrothermal and facile ion-exchange methods, respectively. The powder XRD, FT-IR, SEM-EDS, TEM-SAED, N₂ adsorption-desorption, XPS, UV–Vis DRS, PL and ESR techniques were used to investigate the effect of Gd dopant concentration on the structural and photocatalytic properties of KTO. The photocatalytic activity of these samples was investigated for the photocatalytic degradation of methylene blue (MB) dye in an aqueous solution at room temperature under visible light irradiation. The experimental results show that all Gd-doped KTO samples exhibit enhanced photocatalytic activity compared with parent KTO toward MB degradation. In particular, Gd-KTO obtained by doping of 0.075 mol% shows the highest photocatalytic activity among the Gd-doped samples and the degradation efficiency of MB was 79% after 180 min of visible light irradiation, which is approximately 1.5 times as high as that by parent KTO (53%). In addition, trapping experiments and electron spin resonance (ESR) analysis demonstrated that the hydroxyl radicals (^?OH) have played a crucial role in the photocatalytic degradation of MB. The reusability and stability of Gd doped-KTO with a Gd content of 0.075 mol% against MB degradation were examined for five cycles. Based on the present study results, a visible light induced photocatalytic mechanism has been proposed for Gd0075-KTO sample.     

A new phosphor with flower-like structure and luminescent properties of Sr<Subscript>2</Subscript>MgSi<Subscript>2</Subscript>O<Subscript>7</Subscript>: Eu<Superscript>2+</Superscript>, Dy<Superscript>3+</Superscript> long afterglow materials by sol–gel method

The flower-like phosphors of Sr₂MgSi₂O₇: Eu²⁺, Dy³⁺ with high brightness and long afterglow were obtained by sol–gel method. X-ray diffraction pattern (XRD) shows that single-phased Sr₂MgSi₂O₇ phosphor is prepared by sol–gel method under 1250 °C. Scanning electron microscope (SEM) indicates that the phosphor consists of nano-sized whiskers which are detected for the first time in Eu²⁺ and Dy³⁺ co-doped long-lasting phosphorescence silicates. Furthermore, the investigation on the mechanism indicates that the internal structure and gas, liquid and solid phase effect play important roles in the formation of flower-like Sr₂MgSi₂O₇: Eu²⁺, Dy³⁺ nanostructure. Finally, the optical properties of flower-like Sr₂MgSi₂O₇ nanostructure have been characterized by photoluminescence (PL) spectra.     

Reddish-orange,neutral and warm white emissions in Eu3+, Dy3+ and Dy3+/Eu3+ doped CdO-GeO2-TeO2 glasses

Eu³⁺, Dy³⁺ and Dy³⁺/Eu³⁺ doped CdO-GeO₂-TeO₂ glasses were prepared using the melt-quenching process and analyzed by X-diffraction, Raman spectroscopy, excitation and emission spectra, and emission decay time profiles. The lack of X ray diffraction peaks revealed that all samples are amorphous. Vibrational modes associated with TeOTe and GeOGe related bonds and molecular oxygen were detected by Raman spectroscopy. The luminescence characteristics were studied upon excitations that correspond with the emission of InGaN (370–420 nm) based LEDs. The Eu³⁺ singly doped glass displayed reddish-orange global emission, with x = 0.601 and y = 0.349 CIE1931 chromaticity coordinates, upon 393 nm excitation. Neutral emission with x = 0.373 and y = 0.412 CIE1931 chromaticity coordinates and correlated color temperature (CCT) of 4400 K, was achieved in the Dy³⁺ singly doped glass excited at 388 nm. The Dy³⁺/Eu³⁺ co-doped glass exhibited warm, neutral and soft warm white emissions with CCT values of 3435, 4153 and 2740 K, under excitations at 382, 388 and 393 nm, respectively, depending mainly on the Dy³⁺ and Eu³⁺ relative excitation. The Dy³⁺ excitation bands observed in the Dy³⁺/Eu³⁺ glass by monitoring the 611 nm Eu³⁺ emission, suggest that Dy³⁺ → Eu³⁺ energy transfer takes place, despite the fact that the Dy³⁺ emission decays in the Dy³⁺ and Dy³⁺/Eu³⁺ doped glass, remain without changes. The shortening of Eu³⁺ decay in presence of Dy³⁺ was attributed to an Eu³⁺ → Dy³⁺ non-radiative energy transfer process, which according with the Inokuti-Hirayama model might be dominated through an electric quadrupole-quadrupole interaction, with efficiency and probability of 5.5% and 51.6 s⁻¹, respectively.     

High sensitivity and multicolor tunable optical thermometry in Bi3+/Eu3+ co-doped Ca2Sb2O7 phosphors

Currently, with increasing demand for non-contact fluorescence intensity ratio-based optical thermometry, a novel phosphor with high-efficiency, dual-emitting centers, and differentiable temperature sensitivity is more and more urgent to develop. In this work, an efficient dual-emitting center optical thermometry with high sensitivity and multicolor tunable in Ca₂Sb₂O₇:Bi³⁺, Eu³⁺ phosphor is firstly designed and successfully prepared. Under 330 nm excitation, the fabricated phosphor presents the featured and distinguishable emissions of Bi³⁺ and Eu³⁺ ions. The high efficiency energy transfer from Bi³⁺ to Eu³⁺ ions is proved and its corresponding mechanism belongs to dipole-dipole interaction. By modulating the ratio of Bi³⁺/Eu³⁺, the multicolor changes from blue to pink are realized. Based on the discriminative thermal quenching behavior between Bi³⁺ and Eu³⁺, the fluorescence intensity ratio of Eu³⁺ to Bi³⁺ in Ca₂Sb₂O₇ samples illustrates excellent optical thermometry performance from 298 to 523 K. The maximum absolute sensitivity (S_a) and relative sensitivity (S_r) reach as high as 0.2773 K^?1 at 523 K and 2.37% K^?1 at 448 K, respectively. Notably, the discriminated surrounding temperature can be directly confirmed by observing the emitting color from purple to orange-red with the temperature increase from 298 to 523 K. Furthermore, the as-prepared phosphor materials also demonstrate outstanding repeatability and excellent reversibility. These results exhibit that the designed Ca₂Sb₂O₇:Bi³⁺, Eu³⁺ phosphors have great promising applications in the field of non-contact optical temperature thermometry and thermochromic.     

Photoluminescent properties of white-light-emitting Li6Y(BO3)3:Dy3+ phosphor

In this study, lithium yttrium borate (LYBO) phosphor was doped with various concentrations of trivalent dysprosium ions. To produce these phosphors, the raw materials were sintered. The phase conformation, crystallinity, grain size, and overall morphology of the synthesized phosphors were studied with X-ray diffraction and scanning electron microscopy. The optimized LYBO phosphor, i.e., the LYBO phosphor that exhibited the highest X-ray- and ultraviolet (UV)-induced photoluminescent intensities, had a Dy³⁺ concentration of 4 mol%. Photoluminescence analysis showed that this phosphor could be easily excited with near-UV light (300–400 nm). The dominant photoluminescence bands were found in the blue (480 nm) and yellow (577 nm) regions of the visible spectrum. The light yield of the X-ray-induced luminescence of the optimized Li₆Y(BO₃)₃:Dy³⁺ was found to be 66% of that of the commercially available X-ray imaging material, Gd₂O₂S:Tb³⁺ (GOS). The chromaticity coordinates of the Li₆Y(BO₃)₃:Dy³⁺ phosphor were x = 0.34 and y = 0.32, which agree well with achromatic white (x = 0.33, y = 0.33). The results of this study show that the synthesized Li₆Y(BO₃)₃:Dy³⁺ phosphor could be used as X-ray imaging material.     

Luminescent properties of Sr<Subscript>3</Subscript>Al<Subscript>2</Subscript>O<Subscript>6</Subscript>: Eu,Pr prepared by sol–gel method

A new red-emitting long afterglow Sr₃Al₂O₆: Eu²⁺, Pr³⁺ phosphor was synthesized by sol–gel methods using Sr(NO₃)₂, Al(NO₃)₃·9H₂O, Eu(NO₃)₃ and Pr(NO₃)₃ as raw materials. The crystalline structure of the phosphor powders were characterized by X-ray diffraction. Luminescent properties of the phosphor powders were analyzed by the fluorescence spectrophotometer. Sr₃Al₂O₆: Eu²⁺, Pr³⁺ phosphor powders with single Sr₃Al₂O₆ phase were prepared at 1200 °C for 2 h in the reducing atmosphere. Pr³⁺ doped made the light intensity and the light-lasting time of Sr₃Al₂O₆: Eu²⁺, Pr³⁺ phosphors improved. The emission peaks of the Sr₃Al₂O₆: Eu²⁺, Pr³⁺ phosphor powders lay at 612 nm with the excitation of 472 nm and the longest afterglow time could last for about 15 min at Pr³⁺ content of 0.06.     

Luminescent properties of SrBPO5:Dy3+ and effect of Co-doping with Tm3+

A series of phosphors SrBPO₅:Dy³⁺ and SrBPO₅:Dy³⁺,Tm³⁺ was synthesized by traditional solid-state high-temperature method and was characterized by X-ray diffraction (XRD) and fluorescence spectrophotometry. For SrBPO₅:Dy³⁺ material, the f-f transitions of Dy³⁺ ions were assigned and discussed, and the optimal doping concentration of Dy³⁺ was found. As a result of co-doping SrBPO₅:Dy³⁺ with Tm³⁺, the phosphors SrBPO₅:Dy³⁺,Tm³⁺ can be effectively excited by 360 nm ultraviolet (UV), and exhibit color-tunable emission from blue to yellowish-white region with different doping concentration. The present study can pave the way for the creation of efficient UV phosphors using Dy³⁺,Tm³⁺ co-doped systems for near-UV InGaN-based light emitting diodes (LEDs).     

Optical Spectroscopy and Excited-State Dynamics of Eu3+-Doped Bismuth Borate Glasses Containing CuO

Bismuth borate glasses containing phosphors and luminescent rare-earths are of interest for applications in light-emitting devices. Herein, the influence of CuO impurities on red-emitting Eu³⁺-doped bismuth borate glasses of the 25Bi₂O₃-15BaO-10Li₂O-50B₂O₃ type was investigated by various spectroscopic methods. The glasses were prepared by the melt-quench technique and characterized by X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, UV/Vis optical absorption (OA), and photoluminescence (PL) spectroscopy including decay kinetics assessment. The XRD data confirmed the amorphous nature of the glasses whereas FT-IR spectra indicated the basic structural features of trigonal BO₃ units and BO₄ tetrahedra. The OA analysis showed that addition of CuO up to 0.5 mol% results in significant growth of the visible Cu²⁺ absorption band around 715 nm, with slight decrease in the optical band gap energies assessed through Tauc plots. A drastic PL quenching of Eu³⁺ ions emission was evidenced concurring with the detrimental effect of Cu²⁺. The assessment of the Eu³⁺ emission decay curves revealed significant lifetime decrease of the ⁵D₀ emitting state with increasing CuO concentration. An analysis of quenching constants was finally performed comparing results from integrated PL data with the emission decay rates. It is argued that the bismuth borate glass system supports an effective Eu³⁺→Cu²⁺ energy transfer (more so than phosphates) in connection with a strong spectral overlap between Eu³⁺ emission and Cu²⁺ absorption.     

Photoluminescence Properties of a Promising Red-emitting Phosphor CaNb2O6:EU3+for Trichromatic White Light Emitting Diodes Application

Motivated by the need for new phosphors of white light emitting diode (WLED) application, Ca_0.95Nb₂ O₆:Eu³⁺_0.05 phosphors were synthesized by high temperature solid‐state reaction. Increasing the content of doped‐Eu³⁺ and adding the co‐activator Bi³⁺ to improve the photoluminescence (PL) intensity of Ca_1?xNb₂ O₆Eu³⁺_x phosphors were investigated in detail. The effects of Eu³⁺ were better than that of Bi³⁺ on the PL intensity of Ca_1?xNb₂ O₆Eu³⁺_x phosphors. Compared with Y₂O₂ S:0.05Eu³⁺ the Ca_0.70Nb₂ O₆:Eu³⁺_0.03 phosphor could be excited efficiently by UV (395 nm) light and emit the red light at 614 nm with line spectra, which were coupled well with the characteristic emission from UV‐Near UV LED. The CIE (International Commission on Illumination) chromaticity coordinates (x?0.654, y?0.348) of Ca_0.70Nb₂O₆:Eu³⁺_0.03 were close to the NTSC (National Television Standard Committee) standard values. Therefore Ca_0.70Nb₂ O₆:Eu³⁺_0.03 might find application to UV‐Near UV InGaN chip‐based white light emitting diodes, which is further proved by the LED fabrication with the Ca_0.70Nb₂ O₆:Eu³⁺_0.03 phosphor.     

Fine tuning bifunctional properties of Y0.5Gd0.5BO3 by doping with Ce3+ and co-doping with Li+,Ca2+ and Al3+ following an epoxide mediated gel approach

Realizing the ubiquitous presence of rare-earth orthoborates in various applications involving their optical properties, the current investigation is directed towards the exploration of epoxide mediated rapid synthesis to make YBO₃. Highly crystalline orthoborate with disordered vaterite structure resulted on calcining xerogel from the reaction of yttrium chloride, boric acid and propylene oxide at 900 °C as verified from diffraction, vibration spectroscopic and microscopic techniques. Following this approach, orthoborate containing 50 mol% of Y and Gd was obtained and characterized. Dissolution limit of Ce³⁺ in Y_0.50Gd_0.50BO₃ has been determined. Cerium doping resulted in the reduction in the optical band gap of these samples and appended photocatalytic ability in terms of degradation of aqueous rhodamine-6G (Rh-6G) dye solution. The intensity of 4f → 5d transition of Ce³⁺ increased monotonously with increase in cerium content. The role of distortion on the blue emission from Ce³⁺ and photocatalytic properties of these samples were comprehended by characterizing Li⁺, Ca²⁺ and Al³⁺-doped samples (up to 10 mol%) for yttrium. The distortion of Y_0.50?xM_xGd_0.45Ce_0.05BO₃ lattice decreased in the order, R_Ca2+ > R_Y3+ > R_Li+ > R_Al3+, with the emission intensity (5d → 4f transitions) from Ce³⁺ increasing in the reverse order. Optical band gap was found to decrease for the Li⁺, Ca²⁺ and Al³⁺ doped samples as compared to undoped one. These doped samples retained their catalytic ability as verified from their use in the photo degradation of rhodamine-B (Rh-B) dye. An insight in to possible mechanism operative in the present photo catalytic degradation experiments has been attempted by carrying out trapping experiments.     

稀土离子Tm3+掺杂Bi2WO6的可见光催化性能

以Na₂WO₄·2H₂O和Bi（NO₃）₃·5H₂O为主要原料,采用水热法合成了稀土离子Tm³⁺掺杂的Bi₂WO₆光催化剂。采用XRD、SEM、TEM、Raman、PL、DRS研究了Tm³⁺掺杂Bi₂WO₆的物相,微观形貌和可见光催化性能。结果表明,Tm³⁺掺杂有效提高了Bi₂WO₆的光催化性能,当掺杂量为6%时,样品的光催化性能最好,可见光照射30 min后,对罗丹明B的降解效率达到91.27%,而可见光照射5 h后,对焦糖色素的降解效率达45.25%。与未掺杂Bi₂WO₆相比,分别提高了27.78%和35.22%。     

Investigation of Luminescence Properties of Eu3+, Dy3+ and Gd3+ Doped MgAl2Si2O8 Red‐emitting Phosphors

Rare‐earth‐doped aluminosilicates of alkaline earth MgAl₂Si₂O₈: Eu³⁺, Dy³⁺ and MgAl₂Si₂O₈: Eu³⁺, Gd³⁺ were synthesized by the solid state reaction method at 1300 ^oC. The phosphors were characterized by X‐ray powder diffraction (XRD), photoluminescence (PL), thermoluminescence (TL) and scanning electron microscopy (SEM). X‐ray powder diffraction studies show that the phosphors were crystallized in the triclinic crystal system. The phosphors show characteristic broad band phosphorescence of Eu³⁺. This broad band phosphorescence has red emission bands in the range of 580–705 nm corresponding to ⁵D₀ → ⁷F_j (j:0,2,3,4) transitions of Eu³⁺.     

Effects of boric acid on structural and luminescent properties of BaAl<Subscript>2</Subscript>O<Subscript>4</Subscript>:(Eu<Superscript>2+</Superscript>, Dy<Superscript>3+</Superscript>) phosphors

Eu²⁺/Dy³⁺-codoped BaAl₂O₄ phosphors were prepared by conventional solid-state reaction with boric acid flux. The effects of boric acid on structural and luminescent properties of BaAl₂O₄:(Eu²⁺, Dy³⁺) were investigated. The crystallinity of BaAl₂O₄ improved with increasing amount of H₃BO₃. Incorporation of Eu²⁺ and Dy³⁺ ions into effective lattice sites was promoted by H₃BO₃ addition. As a result, Eu²⁺ emission in BaAl₂O₄ was greatly enhanced by H₃BO₃, and the duration of persistent luminescence increased with the amount of H₃BO₃. However, the decay lifetime of persistent luminescence was not strongly influenced by the amount of H₃BO₃.