Dyand Mn emission in KMgSO4Cl phosphor

In the present paper, KMgSO₄Cl:Ce³⁺, KMgSO₄Cl:Ce³⁺,Dy³⁺, and KMgSO₄Cl:Ce³⁺,Mn²⁺, new halosulphate phosphors were synthesized by wet chemical method. X-ray powder diffraction (XRD) and photoluminescence (PL) characterization of phosphors have been reported in this paper. The effects of Dy³⁺ co-doping on the PL characteristics of KMgSO₄Cl:Ce phosphor were studied. Energy transfer from Ce³⁺→Dy³⁺and Ce³⁺→Mn²⁺ results in increase in PL peak intensity suggesting that Ce³⁺ plays an important role in PL emission in the present matrix. The PL emission spectra have two peaks (482 and 571 nm) and a single peak (564 nm), which could be attributed to the Ce³⁺→Dy³⁺and Ce³⁺→Mn²⁺ emissions, respectively.     

Luminescence investigations on sulfate apatite Na6(SO4)2FCl:RE (RE=Dy, Ce or Eu) phosphors

A new phosphor in the Cl-F system doped with Dy, Ce and Eu has been reported. Characterization of this phosphor using XRD, PL and TL techniques is described. Polycrystalline Na₆(SO₄)₂FCl:Dy; Na₆(SO₄)₂FCl:Ce and Na₆(SO₄)₂FCl:Eu phosphors prepared by a solid state diffusion method have been studied for their X-ray diffraction, photoluminescence (PL) and thermoluminescence (TL)characteristics. The PL excitation and emission spectra of phosphors were obtained. Dy³⁺ emission in the host at 475 and 570 nm is observed due to ⁴F_9/2→⁶H_15/2 and ⁴F_9/2→⁶H_13/2 transition, respectively, whereas the PL emission spectra of Na₆(SO₄)₂FCl:Ce phosphor shows the Ce³⁺ emission at 322 nm due to 5d→4f transition of Ce³⁺ ion. In Na₆(SO₄)₂FCl:Eu lattice, Eu²⁺ as well as Eu³⁺ emissions are observed. The emission of europium ion in this compound exhibits the blue as well as red emission. The TL glow curves of the same compounds have the simple structure with a prominent peak at 150, 175 and 200 °C. TL response, fading, reusability and trapping parameters of the phosphors are also studied. The TL glow curves of γ-irradiated Na₆(SO₄)₂FCl sample show one glow peak indicating that only one set of traps is being activated within the particular temperature range each with its own value of activation energy (E) and frequency factor (s). The trapping parameters associated with the prominent glow peak are calculated using Chen’s half width method. The release of hole/electron from defect centers at the characteristic trap site initiates the luminescence process in these materials. The intensity of the TL glow peaks increases with increase of the added γ-ray dose to the samples.     

Photoluminescence and thermoluminescence characterization of Eu- and Dy -activated Ca3(PO4)2 phosphor

Rare-earth-doped polycrystalline Ca₃(PO₄)₂:Eu, Ca₃(PO₄)₂:Dy and Ca₃(PO₄)₂:Eu,Dy phosphors prepared by a modified solid-state synthesis has been studied for its X-ray diffraction, thermoluminescence (TL) and photoluminescence (PL) characteristics. The PL emission spectra of the phosphor suggest the presence of Eu³⁺ ion in Ca₃(PO₄)₂:Eu and Dy³⁺ ion in Ca₃(PO₄)₂:Dy lattice sites. The TL glow curve of the Ca₃(PO₄)₂:Eu compounds has a simple structure with a prominent peak at 228 °C, while Ca₃(PO₄)₂:Dy peaking at 146 and 230 °C. TL sensitivity of phosphors are compared with CaSO₄: Dy and found 1.52 and 1.20 times less in Ca₃(PO₄)₂:Eu and Ca₃(PO₄)₂:Dy phosphors, respectively. The Ca₃(PO₄)₂:Eu,Dy phosphors shows switching behavior under two different excitation wavelengths and enhancement in PL intensity of Dy³⁺ ions were reported. The paper discusses the photoluminescence and thermoluminescence behavior of Eu³⁺ and Dy³⁺ ion in Ca₃(PO₄)₂ hosts, it may be applicable to solid-state lighting as well as thermoluminescence dosimetry applications.     

Eu and Ce emission in sulphate based phosphors

Polycrystalline KMgSO₄Cl:Eu and Na₅(PO₄)SO₄:Ce phosphors prepared by a wet chemical method have been studied for its photoluminescence (PL) and thermoluminescence (TL) characteristics. The TL glow curve of the compound has a prominent peak at 200 °C and may be useful for TL study. TL sensitivity of the KMgSO₄Cl:Eu phosphor is found to be 1.7 times less than that of TLD—CaSO₄:Dy. The presence of bands at around 420, 435 and 445 nm in the PL emission spectra of the phosphor suggests the presence of Eu²⁺ in the host compound. Moreover a TL glow curve of the Na₅(PO₄)SO₄:Ce gives a better understanding of the TL mechanism (peaks at 271 and 310 °C) involved in the concerned phosphor. The PL emission spectra are observed at 382 nm for the various concentrations. In this paper we report PL and TL characteristics of KMgSO₄Cl:Eu halosulphate and Na₅(PO₄)SO₄:Ce phosphate sulphate phosphors first time.     

Luminescence and evaluation of trapping parameters in NaMgSO4Cl: X (X=Cu or Ce) phosphor

Thermoluminescence (TL) characteristics of recently developed high sensitive mixed halosulphate phosphors, NaMgSO₄Cl: Cu and NaMgSO₄Cl: Ce were studied in comparison with CaSO₄: Dy in order to assess the possibility of their use in personal monitoring and TLD phosphors at very low dose of 5 Gy. It was found that NaMgSO₄Cl: Cu is 5.59 times and NaMgSO₄Cl: Ce is 6.18 times more sensitive as compared to standard CaSO₄: Dy. UV photo-excited luminescence from Cu to Ce doped NaMgSO₄Cl halosulphate phosphors has been investigated. The intense emission of the spectrum is assigned to electronic transitions 3d⁹4s¹→3d¹⁰ in monovalent copper ion and 5d→4f in Ce³⁺ ions. Increase in PL peak intensity suggesting that Cu and Ce play an important role in PL emission in the present matrix. These phosphors were synthesized by the wet chemical method. XRD, photoluminescence (PL) and thermoluminescence (TL) characterization of phosphors has been reported in this paper. The preparation of an inexpensive and high sensitive NaMgSO₄Cl: Cu and NaMgSO₄Cl: Ce with TL glow peaks for different concentrations are observed between 160 and 195 °C and between 200 and 225 °C, respectively, exposed to gamma-rays of ⁶⁰Co for their thermoluminescence (TL) properties. The glow curves have been recorded at a heating rate of 2 K s^?1 and irradiated at a dose rate of 0.995 kGy h^?1 for 5 Gy. In present study the trapping parameters such as order of kinetics (b), activation energy (E) and frequency factors (s) have been calculated for the 195 and 200 °C glow peaks of NaMgSO₄Cl: Cu and NaMgSO₄Cl: Ce, respectively by using Chen's method. The paper discusses the luminescence of Cu⁺ and Ce³⁺ by simple method of incorporation in NaMgSO₄Cl host.     

Luminescence in trivalent rare earth activated Sr4Al2O7 phosphor

In this paper we report the combustion synthesis of trivalent rare-earth (RE³⁺ = Dy, Eu and Ce) activated Sr₄Al₂O₇ phosphor. The prepared phosphors were characterized by the X-ray powder diffraction (XRD) and photoluminescence (PL) techniques. Photoluminescence emission peaks of Sr₄Al₂O₇:Dy³⁺ phosphor at 474 nm and 578 nm in the blue and yellow region of the spectrum. The prepared Eu³⁺ doped phosphors were excited by 395 nm then we found that the characteristics emission of europium ions at 615 nm (⁵D₀?⁷F₂) and 592 nm (⁵D₀?⁷F₁). Photoluminescence (PL) peaks situated at wavelengths of 363 and 378 nm in the UV region under excitation at around 326 nm in the Sr₄Al₂O₇:Ce³⁺ phosphor.     

Rare earth doped lithium titanate (Li2TiO3) for potential phosphor applications

Lithium titanate ceramics doped with three rare earth (RE) ions namely Eu³⁺, Dy³⁺ and Tb³⁺ were synthesized and their photoluminescence (PL) properties were investigated. PL spectra of Eu doped sample showed peaks corresponding to the ⁵D₀→⁷F_j (j=0, 1, 2, 3 and 4) transitions under 230 nm excitation. Strong red emission coming from the hypersensitive ⁵D₀→⁷F₂ transition of Eu³⁺ ion suggested the presence of the dopant ion in a highly asymmetric environment. Dy doped samples showed the Dy³⁺ emission characteristic due to ⁴F_9/2→⁶H_15/2 and ⁴F_9/2→⁶H_13/2 transitions. Their relative intensity ratios also suggested the presence of asymmetric environment around the metal ion. In case of the Tb³⁺ doped sample blue-green emission corresponding to the ⁵D₄→⁷F_j (j=6, 5 and 4) transitions was seen. The fluorescence lifetimes of Eu³⁺, Dy³⁺ and Tb³⁺ ions were found to be 645, 900 and 740 μs, respectively. PL intensity of the individual rare earth doped samples was compared with commercial red and green phosphors. It was found that the emission from Eu doped titanate sample was 46% of the commercial red phosphor and in case of the Tb samples it was 30% when excited at 230 nm. However, the synthesized Eu doped titanate sample showed better color purity as compared to the commercial phosphor. The titanate host was doped with all the three rare earths to get white light emission from the system. The individual rare earth ion content was optimized so as to get a near white light emission. The color coordinates of the triple doped systems were evaluated and plotted on the CIE x–y diagram. Our results suggest that lithium titanate has enough potential to be a phosphor material.     

Synthesis and effect of Ce co-doping on photoluminescence characteristics of KZnSO4Cl: M (M=Dy or Mn) new phosphors

In the present paper KZnSO₄Cl:Ce³⁺, KZnSO₄Cl:Ce³⁺, Dy³⁺ and KZnSO₄Cl:Ce³⁺, Mn²⁺ new halosulfate phosphors were synthesized by wet chemical method. XRD and photoluminescence characterization of phosphors has been reported in this paper.     

Correlation of photoluminescence of (Y, Ln)VO4:Eu (Ln=Gd and La) phosphors with their crystal structures

We have studied the photoluminescence (PL) of (Y, Ln)VO₄:Eu³⁺ (Ln=La and Gd) phosphors and the correlation of the PL of those phosphor with their crystal structure. It is found that (Y, Gd)VO₄:Eu³⁺ phosphors have the same crystal structure as YVO₄:Eu³⁺, which is tetragonal with a little different lattice parameters. In the case of (Y, La)VO₄:Eu³⁺ phosphors, however, the gradual change from tetragonal to monoclinic structure of host lattice was observed as the amount of La ion increased. To investigate the PL property of (Y, Ln)VO₄:Eu³⁺ (Ln=La and Gd) phosphors, vacuum ultraviolet (VUV) and ultraviolet (UV) excitation were used. The favorable crystal structure for the PL intensity of orthovanadate phosphor under 147 and 254 nm excitation was tetragonal containing Gd ion and under 365 nm excitation was monoclinic containing La ion which might have the lowest site symmetry for Eu³⁺ ion.     

Enhanced luminescence of Tb by efficient energy transfer from Ce in Sr2B5O9Cl host

Ce³⁺ and Tb³⁺ co-doped Sr₂B₅O₉Cl phosphors with intense green emission were prepared by the conventional high-temperature solid-state reaction technique. A broad band centered at about 315 nm was found in phosphor Sr₂B₅O₉Cl: Ce³⁺, Tb³⁺ excitation spectrum, which was attributed to the 4f-5d transition of Ce³⁺. The typical sharp line emissions ranging from 450 to 650 nm were originated from the ⁵D₄ → ⁷F_J (J = 6, 5, 4, 3) transitions of Tb³⁺ ions. The photoluminescence (PL) intensity of green emission from Tb³⁺ was enhanced remarkably by co-doping Ce³⁺ in the Tb³⁺ solely doped Sr₂B₅O₉Cl phosphor because of the dipole-dipole mechanism resonant energy transfer from Ce³⁺ to Tb³⁺ ions. The energy transfer process was investigated in detail. In light of the energy transfer principles, the optimal composition of phosphor with the maximum green light output was established to be Sr_1.64Ce_0.08Tb_0.1Li_0.18B₅O₉Cl by the appropriate adjustment of dopant concentrations. The PL intensity of Tb³⁺ in the phosphor was enhanced about 40 times than that of the Tb³⁺ single doped phosphor under the excitation of their optimal excitation wavelengths.     

不同形貌的LaPO4：Dy荧光粉的制备及其真空紫外激发下的发光性能

在水热法中通过改变磷源以及反应溶剂成功合成出了不同形貌的LaPO₄：Dy荧光粉,考察了真空紫外激发下不同形貌的LaPO₄：Dy荧光粉的发光性能.结果表明,由于采用的磷源不同,不同形貌的LaPO₄：Dy荧光粉的发光强度会受到影响;其次颗粒尺寸的大小也会影响发光强度.而形貌对Dy³⁺离子占据的格位的对称性影响不大,三种形貌的LaPO₄：Dy荧光粉的黄蓝比都在1—1.5之间.从激发光谱的对比中可知LaPO₄基质向Dy³⁺离子传递能量的效率不如向其他稀土离子,如Eu³⁺离子的效率高,同时在激发光谱中还观察到了较强的Dy³⁺离子的f-d跃迁激发峰. 关键词： 3+')" href="#">Dy³⁺ 真空紫外 发光     

Solid state metathesis of CaSO4:Eu2+ phosphor

CaSO₄:Dy, is a well known phosphor for radiation dosimetry using thermoluminescence. CaSO₄:Eu³⁺ and CaSO₄:Eu²⁺ phosphors also find applications in radio-photoluminescence dosimetry and photoluminescent liquid crystal displays (PLLCD), respectively. Various syntheses of these phosphors are known. In this paper solid state metathesis of CaSO₄:Eu using domestic microwave oven is described for the first time. The synthesis is fast, the entire process being completed within few minutes. The phosphor is characterized using XRD and PL techniques.     

Enhanced blue emission and EPR study of LaMgAl11O19:Eu phosphors

Europium doped LaMgAl₁₁O₁₉ phosphor was prepared by the combustion method. The as-prepared and post-treated (1350 °C 10 h 5% H₂+95% N₂) phosphors were investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), photoluminescence (PL) and electron paramagnetic resonance (EPR) techniques. XRD patterns show that LaMgAl₁₁O₁₉:Eu phosphors have hexagonal structure. FT-IR spectrum exhibits absorption bands corresponding to the stretching vibration of AlO₄ and AlO₆. Morphological studies reveal that this phosphor has faceted plates of varying sizes and shapes. The as-prepared LaMgAl₁₁O₁₉:Eu phosphor consists of both Eu³⁺ and Eu²⁺ ions. The phosphor exhibits a bright blue emission at 450 nm (4f⁶5d→4f⁷ transition of Eu²⁺). On post-treating the phosphor we are able to enhance the blue emission efficiency by 330%. The process was detected from the evolution of excitation, emission and EPR spectra and the results are discussed.     

Effect of Tb3+ co-doping and particle size on K2Ca2(SO4)3:EU phosphor

K₂Ca₂(SO₄)₃ doped with Eu, and co-doped with Tb were prepared by the solid state diffusion method. The nanoparticles of these phosphors were also prepared by the chemical co-precipitation method. The formation of the compounds was confirmed by XRD. The particle size was calculated by the broadening of the XRD peaks using Scherrer's formula. The particle size was found to be around 20?nm. Thermoluminescence (TL) was studied to see the effect of co-doping and particle size. Tb³⁺ co-doping decreases the intensity in the Eu²⁺ doped phosphor due to the energy transfer and multiple de-excitations through various radiative and non-radiative processes. The K₂Ca₂(SO₄)₃:Eu,Tb phosphor is found to be 0.33 times more sensitive than TLD-700H, but around 15 times more than LiF-TLD 100, and 7 times more than CaSO₄:Dy. The effective atomic number Z_eff is around 15, which is again comparable to CaSO₄:Dy.

However, very low sensitivity was observed in the case of nanoparticles. The decrease in the sensitivity is attributed to the particle size effect i.e., the volume-to-surface ratio. Study of photoluminescence (PL) of the material is also carried out.     

UV-induced photoluminescence and thermally stimulated luminescence of CaSO4:Eu and CaF2:Tb3+ phosphors

Ultraviolet radiation induced changes in photoluminescence (PL) and thermally stimulated luminescence (TSL) of europium activated calcium sulphate (CaSO₄:Eu³⁺, Eu²⁺) and terbium doped calcium fluoride (CaF₂:Tb³⁺) phosphors have been studied. PL measurements suggest conversion of Eu³⁺ to Eu²⁺ on 254 nm irradiation corresponding to charge transfer band of Eu³⁺ ions and reduction of Eu²⁺ ions with 365 nm illumination representing a f–d transition of Eu²⁺ ions. Similar studies carried out on CaF₂:Tb³⁺ phosphor, however, do not show any significant wavelength specific changes. The integrated TSL output appears to be rate-dependent for both phosphors. The wavelength dependent changes in TSL output observed for CaSO₄:Eu phosphor have been correlated with those obtained in PL studies. The changes in TSL and PL characteristics of CaF₂:Tb³⁺ phosphor have been explained on the basis of stabilisation of traps based on matrix specific charge similarities.     

5d→4f transition in halosulphate phosphors

The synthesis, X-ray diffraction and photoluminescence characteristics in alkaline halosulphate phosphors, such as KZnSO₄Cl:Ce; KMgSO₄Cl:Ce; NaMgSO₄F:Ce and Na₃SO₄F:Ce is reported in this paper. The Ce³⁺ emission in KMgSO₄Cl:Ce phosphor is maximum and it may be useful for scintillation applications.     

Luminescent properties of Dy doped SrMoO4 phosphor

Trivalent dysprosium ions (Dy³⁺) doped strontium molybdate (SrMoO₄) phosphors were synthesized by solid-state reaction and their photoluminescence (PL) properties were investigated. X-ray powder diffraction (XRD) analysis confirmed the formation of SrMoO₄:Dy³⁺. PL measurements indicated that the phosphor exhibited intense emission at 482, 490 (⁴F_9/2→⁶H_15/2) and 575 nm (⁴F_9/2→⁶H_13/2) under UV excitation. The effect of the doping concentration of Dy³⁺in SrMoO₄:Dy³⁺ on the PL was investigated in detail. Na⁺ ion was a good charge compensator for SrMoO₄:Dy³⁺.     

Photoluminescence characterization of Ce and Dy doped Li2CaGeO4 phosphors

Ce³⁺ and Dy³⁺ activated Li₂CaGeO₄ phosphors were prepared by a solid-state reaction method, and characterized by XRD (X-ray diffraction) and photoluminescence techniques. The characteristic emission bands of Dy³⁺ due to ⁴F_9/2→⁶H_15/2 (blue) and ⁴F_9/2→⁶H_13/2 (yellow) transitions were detected in the emission spectra of Li₂CaGeO₄:Dy³⁺. Ce³⁺ broad band emission was observed in Li₂CaGeO₄:Ce³⁺ phosphors at 372 and 400 nm due to 5d→4f transition when excited at 353 nm. Co-doping of Ce³⁺ enhanced the luminescence of Dy³⁺ significantly and concentration quenching occurs when Dy³⁺ is beyond 0.04 mol%. White-light with different hues can be realized by tuning Dy³⁺ concentration in the phosphors.     

Photoluminescence of Eu single doped and Eu/Dy codoped Sr2Al2SiO7 phosphors with long persistence

This paper reports the preparation of long persistent Sr₂Al₂SiO₇:Eu²⁺ and Sr₂Al₂SiO₇:Eu²⁺, Dy³⁺ phosphors and the comparison of their photoluminescent properties. The silicate phosphors prepared by solid-state reaction routine showed a broad blue emission peaking at 484 nm when activated by UV illumination. Such a bluish-green emission can be attributed to the intrinsic 4f-5d transitions of Eu²⁺. After the UV source was switched off, long persistent phosphorescence could be observed by naked eyes for both samples in darkness. Afterglow measurements revealed that Eu/Dy codoped phosphor possesses better afterglow properties than the Eu single doped one, since the maximum lifetime (τ_max=99 s) of the photons calculated from the decay profile is much larger than that of the Eu single doped phosphor (τ_max=82 s). TSL results suggested that the difference in afterglow properties was caused by the difference in the electron traps within the crystal lattice. For Eu/Dy codoped phosphor, the doping of Dy ions produced electron traps with trap depth of 0.52 eV, which is suitable and therefore leads to good persistence. However, in the case of Eu single doped phosphor, the trap depth is 0.88 eV, which is really too deep an energy barrier to overcome, and therefore a poor persistence was observed in the experiment.     

Photoluminescence studies of NaCaPO4:RE (RE=Dy, Mn or Gd)

The purpose of the present study is to develop an understanding of photoluminescence properties of Dy³⁺, Mn²⁺ or Gd³⁺doped NaCaPO₄ phosphors, which have served as efficient phosphors in many industrial applications. The phase formation was confirmed by the X-ray powder diffraction (XRD) measurement. Photoluminescence (PL) excitation spectrum measurement of NaCaPO₄:Dy³⁺ shows this phosphor can be efficiently excited by near-ultraviolet (UV) light from 300 to 400 nm and presents dominant luminescence band centered at 480 nm (blue) and 573 nm (yellow). The PL excitation of NaCaPO₄:Mn²⁺ and Gd³⁺ under UV wavelength shows the emissions at 520 and 313 nm, respectively. A scanning electron microscope (SEM) shows an average crystallite size in sub-micrometer range. The obtained results show that the phosphors have the potential for application in the lamp industry and medical applications.