共查询到20条相似文献,搜索用时 15 毫秒
1.
R.B. Jabbarov B.G. Tagiev N.N. Musayeva P. Benalloul 《Journal of Physics and Chemistry of Solids》2005,66(6):1049-1056
A photoluminescence study of the blue-green emitting BaGa2S4:Eu2+ phosphor is reported. Diffuse reflectance, excitation and emission spectra were examined with the aim to enlarge the fundamental knowledge about the emission of the Eu2+ rare earth ion in this lattice. The thermal dependence of the radiative properties and the influence of the Eu2+ concentration were investigated. The Stokes shift, the crystal field splitting and the activation energy of the thermal quenching were determined. By combining these results with data available in literature, we discussed the radiative properties of the BaAl2S4:Eu2+ blue phosphor in relation with those determined in this study for the isostructural BaGa2S4:Eu2+ phosphor. 相似文献
2.
Junjun Zhang Linlin Li Wenwen Zi Na Guo Lianchun Zou Shucai Gan Guijuan Ji 《Journal of Physics and Chemistry of Solids》2014
Tetragonal CaMoO4 and CaMoO4:Eu3+ with various novel three-dimensional (3D) hierarchical architectures were successfully synthesized via a facile, efficient sonochemistry process in the absence of any surfactant or template. XRD, EDS, FE-SEM, and photoluminescence (PL) were employed to characterize the as-obtained products. It was found that morphology modulation could be easily realized by changing pH value of the precursor. The pH value of the precursor not only affected the substructures of the hierarchical structures, but also determined the size distributions of the final products. The formation mechanism for different hierarchical architectures was proposed on the basis of time-dependent experiments. The luminescence spectra showed that CaMoO4:Eu3+ phosphors can be effectively excited by the near ultraviolet (UV) (396 nm) and blue (466 nm) light, and exhibited strong red emission around 615 nm, which was attributed to the Eu3+5D0→7F2 transition. Compared with Y2O3:Eu3+ phosphor, CaMoO4:Eu3+ is much more stable, efficient and suitable, therefore, this phosphors could be a promising red component for possible applications in the field of LEDs. 相似文献
3.
Multi-color long lasting phosphorescent (LLP) phenomenon in β-Zn3(PO4)2:Mn2+,Zr4+ was systematically investigated. It is found that the red (λEm=616 nm) LLP performance of Mn2+ such as brightness and duration is largely improved, and that the blue (λEm=475 nm) LLP of Zr4+ with lower intensity appears when Zr4+ ions are co-doped into the matrix. The fluorescence, phosphorescence and thermoluminescence (TL) spectra show that Mn2+ ion is solely expected as a luminescent center, while Zr4+ ion not only acts as a luminescent center, but also induces an electron trap (TrapZr) associated with a TL peak at 344 K. The trap depth for TrapZr is 0.25 eV, while that for the intrinsic trap is 0.38 eV, associated with a dominant peak at 385 K for Zn3(PO4)2:Mn2+. The Zr4+-induced trap with suitable depth is responsible for the improvement of the red LLP of Mn2+ ion and the appearance of the blue LLP of Zr4+ ion. The LLP mechanism is also investigated. 相似文献
4.
Chaofeng Zhu Guorong Chen S. Baccaro M. Falconieri 《Journal of Physics and Chemistry of Solids》2007,68(9):1721-1724
Y2O3:Eu3+ phosphor is a very attractive material for use as a red phosphor in many fields. SrAl2O4:Eu2+ belongs to long lasting phosphor (LLP) and it is a useful bluish-green luminescence material, which can also be a promising candidate as a simple and easy-to-use radiation detection element for visual display of two dimensional radiation distributions. In the present study, both these two kinds of phosphors were synthesized using high temperature solid state reactions. In our work, the influence of gamma-ray irradiation on the properties of these two kinds of phosphors was studied by comparing photoluminescence, brightness and the decay curve of unirradiated and gamma-ray-irradiated samples. Conclusions from the present work can be briefly summarized as follows. In irradiated samples, the brightness is decreased without sensible change in the wavelength distribution of the luminescence spectrum and in the decay kinetic upon gamma exposure. Moreover, the emission due to Eu3+→Eu2+ conversion in Y2O3:Eu3+ phosphors was not observed in our sample after irradiation to high exposure. Also the brightness of SrAl2O4:Eu2+ phosphor turned out to decrease after the exposition to ionizing radiation while the luminescence wavelength distribution remained unchanged. The reason for the effect of gamma-ray irradiation on the properties of phosphors is also discussed in the paper. 相似文献
5.
Given the recent increased interest in phosphor materials and their applications, we analyzed a new NaPbB5O9:Dy3+ phosphor material with different concentrations of Dy3+. In particular, we investigated the crystal structure, morphology, and luminescence properties of these materials. X-ray diffraction analyses confirmed the formation of NaPbB5O9:Dy3+ phosphor powder. The functional groups present in the phosphor materials were examined by Fourier transform infrared spectroscopy. Scanning electron microscope images showed that the size of the grains was in the micrometer range. Photoluminescence spectra were recorded at different excitation wavelengths for the phosphor materials and we analyzed the variation in the intensity of the emission bands with different concentrations of Dy3+ ions. The color co-ordinates were calculated and used to characterize the color of the phosphor. We found that the emission colors of the Dy3+-doped NaPbB5O9 powders depended on the Dy3+ ion doping concentration and the excitation wavelength. 相似文献
6.
A series of red phosphors R0.8Eu1.2(MoO4)3 (R=La, Y, and Gd) have been synthesized by sol-gel method. The crystallization processes of the phosphor precursors were characterized by X-ray diffraction (XRD) and thermogravimetry-differential thermal analysis (TG-DTA), and the properties of these resulting phosphors have also been characterized by photoluminescence (PL) spectra and reflectance spectra. Field emission scanning electron microscopy (FE-SEM) was also used to characterize the shape and the size of the samples. The results of TG-DTA and XRD indicated that all of the R0.8Eu1.2(MoO4)3 (R=La, Y, and Gd) phosphors crystallized completely at 650 °C. Y0.8Eu1.2(MoO4)3 and Gd0.8Eu1.2(MoO4)3 have two structures, monoclinic and orthorhombic, while La0.8Eu1.2(MoO4)3 only adopts monoclinic structure. The luminescent properties of phosphors R0.8Eu1.2(MoO4)3 (R=La, Y, and Gd) are dependent on their structures to some extent. The orthorhombic Y0.8Eu1.2(MoO4)3 and Gd0.8Eu1.2(MoO4)3 phosphors show very similar luminescent properties, which differ from those of phosphors with monoclinic structure. For all of R0.8Eu1.2(MoO4)3 (R=La, Y, and Gd) phosphors, intense red emission is obtained by exciting at ∼394 and ∼465 nm which are owing to the sharp 7F0→5L6 and 7F0→5D2 lines of Eu3+. Two strongest lines at 394 and 465 nm in excitation spectra of these phosphors match well with the two popular emissions from near-UV and blue GaN-based LEDs, so they could be used as red components for white light-emitting diodes. 相似文献
7.
BaMgAl10O17:Eu2+ phosphors were synthesized by the flux method. When the appropriate amounts of fluxes are added, the synthesis temperature reduced by at least 200 °C compared with the conventional solid-state reaction method. SEM images demonstrated that addition of the flux in the process of phosphor synthesis benefitted the size and morphology of BaMgAl10O17:Eu2+ phosphor particles. Photoluminescence measurements under VUV excitation indicated that the luminescent intensity of the phosphor enhanced by adding the flux system (BaF2+Li2CO3). Addition of the flux system can not only enhance the luminescence efficiency and improve the stability, but also control the morphology and grain size of the phosphor. Replacement of Ba2+ by Li+ could generate traps, which result in slightly longer decay time. 相似文献
8.
Ran Pang Chengyu Li Lili Shi Qiang Su 《Journal of Physics and Chemistry of Solids》2009,70(2):303-306
By introducing the Y3+ into Sr2P2O7:Eu2+, we successfully prepared a kind of new phosphor with blue long-lasting phosphorescence by the high-temperature solid-state reaction method. In this paper, the properties of Sr2P2O7:Eu2+,Y3+ were investigated utilizing XRD, photoluminescence, luminescence decay, long-lasting phosphorescence and thermoluminescence (TL) spectra. The phosphor emitted blue light that was related to the 4f65d1-8S7/2 transition of Eu2+. The bright blue phosphorescence could be observed by naked eyes even 8 h after the excitation source was removed. Two TL peaks at 317 and 378 K related to two types of defects appeared in the TL spectrum. By analyzing the TL curve the depths of traps were calculated to be 0.61 and 0.66 eV. Also, the mechanism of LLP was discussed in this report. 相似文献
9.
The white-light long-lasting phosphors Y2O2S:Tb3+, Sr2+ or/and Zr4+ were prepared and studied. The white-light afterglow emission after the irradiation with 254 nm UV are composed of the blue light emission and the yellowish-green light emission, originating from the transitions of 5D3→7F5, 5D4→7F5 in Tb3+ when the Tb3+ concentration is not higher than 0.3 at%. The codoped Sr2+ and Zr4+ ions act as trap-creating ions. The afterglow can last over 21 min in the dark for Y2O2S:Tb3+0.3%, Sr2+4%, Zr4+4% after irradiation by 254 nm ultraviolet light. Y2O2S:Tb3+ may be a promising material for the development of white-light long-lasting phosphor since the Tb3+ has a high luminescent efficiency and the dominant excitation band of 4f →5d is located at 220-300 nm. 相似文献
10.
L. Pidol O. Guillot-Noël B. Viana D. Gourier 《Journal of Physics and Chemistry of Solids》2006,67(4):643-650
Two Ce3+-doped scintillator crystals, LSO (Lu2SiO5:Ce) and LPS (Lu2Si2O7:Ce), are studied by EPR spectroscopy. The analysis indicates that Ce3+ substitutes for Lu3+ ion in a C2-symmetry site for LPS and in two C1-symmetry sites for LSO, with a preference for the largest one, with 6+1 oxygen neighbors. Angular dependence of the EPR spectrum shows that the electronic ground state of Ce3+ is different in these two matrices. It is mainly composed of |MJ|=5/2 state in LPS and |MJ|=3/2 state in LSO. The temperature dependence of the linewidth shows a noticeably long spin lattice relaxation time, especially in LPS, which is the result of a stronger crystal field in LPS than in LSO. 相似文献
11.
E. Quintero E. Moreno M. Morocoima P. Grima P. Bocaranda M.A. Macías 《Journal of Physics and Chemistry of Solids》2010,71(7):993-735
Magnetic susceptibility χ measurements in the range from 2 to 300 K were carried out on samples of the Cu2FeSnSe4 and Cu2MnSnSe4 compounds. It was found that Cu2FeSnSe4 was antiferromagnetic showing ideal Curie-Weiss behavior with a Néel temperature TN of about 19 K and Curie-Weiss temperature θ=−200 K, while for Cu2MnSnSe4 the behavior was spin-glass with a freezing temperature Tf of about 22 K and Curie-Weiss temperature θ=−25 K. The spin-glass order parameter q(T), determined from the susceptibility data, was found to be in agreement with the prediction of conventional spin-glass theory. 相似文献
12.
Haoyi Wu Yihua Hu Bodai Zeng Zhongfei Mou Liuyong Deng 《Journal of Physics and Chemistry of Solids》2011,72(11):1284-1289
The long afterglow phosphors Sr1.97−xBaxMgSi2O7:Eu2+0.01, Dy3+0.02 (x=0, 0.4, 0.8, 1.2, 1.6 and 1.97) were synthesized via high temperature solid-state reaction. The phase identification reveals that the crystal plane spacing becomes greater with the decrease in the Sr/Ba ratio. Phase transition occurs when x=1.97. A nonlinear relationship between the emission peak and the crystal plane spacing is obtained with the decrease of the Sr/Ba ratio. This ascribes to the splitting of the 5d level of the Eu2+ and the change of the crystal field strength. The duration of the afterglow becomes shorter with the decrease of the Sr/Ba ratio. It may ascribe to deeper trap depth, lower trap concentration and the embarrassment of the transfer of carriers. 相似文献
13.
T.K. Seshagiri T.K. Gundu Rao V. Natarajan S.V. Godbole 《Journal of Physics and Chemistry of Solids》2009,70(9):1261-1266
Yttrium borate doped with uranium was prepared by mixing and heating yttrium oxide obtained through oxalate precipitation route, boric acid and requisite amount of nuclear-grade uranium oxide at high temperature. Photoluminescence (PL), thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) studies were carried out on gamma-irradiated doped/undoped yttrium borate samples in the temperature range 300-600 K. TSL studies showed the presence of two glow peaks at 414 and 471 K. PL studies along with lifetime decay investigation suggested uranium goes in the matrix as UO22+. EPR studies showed the presence of O2−radical ion along with electron trapped in defect centres, which might have been produced for charge compensation. Apart from this, CO2− radical was also observed in the system having its origin from residual oxalate ion. Temperature dependence EPR studies of the observed radical confirmed the involvement of the CO2− and dioxide radical ion in the observed glow peaks. By correlating the TSL, PL and ESR data, probable mechanism is proposed for the observed TSL glow in the system. 相似文献
14.
G.R. Dillip K. Mallikarjuna S.J. Dhoble B. Deva Prasad Raju 《Journal of Physics and Chemistry of Solids》2014
A red-emitting phosphor NaSrB5O9:Eu3+ was synthesized by employing a solid-state reaction (SSR) method. The structures of the phosphors were analyzed by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) and Raman studies. The band at ~282 nm in the excitation spectra indicated the charge transfer band (CTB) of B-O in the host, whereas the CTB of Eu-O was observed at ~275 nm for the NaSrB5O9:Eu3+ (Eu3+=1 at.%) phosphor, which was supported by diffuse reflectance spectroscopy (DRS) measurements. The photoluminescence (PL) measurements exhibited a strong red emission band centered at about 616 nm (5D0→7F2) under an excitation wavelength of 394 nm (7F0→5L6). Upon host excitation at 282 nm, the pristine NaSrB5O9 exhibited a broad UV emission centered at ~362 nm. The energy transfer from host to Eu3+ ions was confirmed from luminescence spectra, excited with a 355 nm Nd:YAG laser. In addition, the asymmetric ratios indicate a higher local symmetry around the Eu3+ ion in the host. The calculated CIE (Commission International de l′Eclairage) coordinates displayed excellent color purity efficiencies (around 99.7%) compared to other luminescent materials. 相似文献
15.
H.O. Rodrigues G.F.M. Pires Junior J.S. Almeida A.C. Ferreira M.A.S. Silva 《Journal of Physics and Chemistry of Solids》2010,71(9):1329-2539
In this paper we studied the effects of Bi2O3 and PbO addition on BiFeO3 (BFO) ceramic matrix. The structural, dielectric and magnetic properties of fifteen BFO samples were discussed in view of possible applications in RF and microwave devices. The present work also reports the preparation of the samples. Polyvinyl alcohol (PVA) and tetraethyl orthosilicate (TEOS) were also added as a binder in the fabrication procedure. The samples have been studied by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and magnetic hysteresis measurements. Further, a study based on impedance spectroscopy also has been done. Dielectric permittivity (ε′) and dielectric loss (tan δ) were measured at room temperature in the frequency range 100 Hz-10 MHz, as well as a.c. conductivity. The -Im[Z(f)] versus Re[Z(f)] plot has been obtained. The samples were investigated in view of possible applications like miniaturized filters, diplexers and dielectric resonator antennas (DRA). In the RF and MW frequency region, the application of magneto-dielectric and multiferroic perovskite composite materials is desirable for the miniaturization of components. 相似文献
16.
Z.X. Cheng S.J. ZhangF. Song H.C. GuoJ.R. Han H.C. Chen 《Journal of Physics and Chemistry of Solids》2002,63(11):2011-2017
Erbium and ytterbium codoped double tungstates NaY(WO4)2 crystals were prepared by using Czochralski (CZ) pulling method. The absorption spectra in the region 290-2000 nm have been recorded at room temperature. The Judd-Ofelt theory was applied to the measured values of absorption line strengths to evaluate the spontaneous emission probabilities and stimulated emission cross sections of Er3+ ions in NaY(WO4)2 crystals. Intensive green and red lights were measured when the sample were pumped by a 974 nm laser diode (LD), especially, the intensities of green upconversion luminescence are very strong. The mechanism of energy transfer from Yb3+ to Er3+ ions was analyzed. Energy transfer and nonradiative relaxation played an important role in the upconversion process. Photoexcited luminescence experiments are also fulfilled to help analyzing the transit processes of the energy levels. 相似文献
17.
The influence of reducing annealing and repeated oxidizing annealing of the Li2B4O7:Mn single crystals on their thermostimulated luminescence (TSL) and X-ray luminescence (XL) has been studied. Because of the oxygen vacancies formation and the dopant ions reduction, the reducing annealing results in a drastic decrease of the luminescence intensity along with the simultaneous shift of a part of the maxima and redistribution of the peak intensities. The repeated annealing in the oxidizing environment leads only to the partial reduction of the luminescent properties of the Li2B4O7:Mn crystals. 相似文献
18.
Pooja Varshney Sarita Afaq Ahmad Saba Beg 《Journal of Physics and Chemistry of Solids》2006,67(11):2305-2309
Electrical conductivity of ZrO2 doped with Pb3O4 has been measured at different temperatures for different molar ratios (x=0, 0.01, 0.02, 0.03, 0.04, 0.05 and 0.06). The conductivity increases due to migration of vacancies, created by doping. The conductivity increases with increase in temperature till 180 °C and thereby decreases due to collapse of the fluorite framework. A second rise in conductivity at higher temperatures beyond 500-618 °C is due to phase transition of ZrO2. DTA and X-ray powder diffraction were carried out for confirming doping effect and transition in ZrO2.The addition of Pb3O4 to ZrO2 shifted the phase transition of ZrO2 due to the interaction between Pb3O4 and ZrO2. 相似文献
19.
Keishi Kanada Akira Oosawa Takao Suzuki Hirotaka Manaka 《Journal of Physics and Chemistry of Solids》2007,68(11):2191-2194
The ground state of the solid solution of the two spin gap systems (CH3)2CHNH3CuCl3 and (CH3)2CHNH3CuBr3 has been investigated by 1H NMR. The existence of a magnetic ordering in the sample with the Cl-content x=0.85 was clearly demonstrated by a drastic splitting in a resonance line at low temperatures below TN=13.5 K. The observed NMR spectra in the ordered state was qualitatively consistent with the simple antiferromagnetic state. 相似文献
20.
Yong Sun Won 《Journal of Physics and Chemistry of Solids》2010,71(12):1742-1745
The supercells of pure and Eu-doped Sr2SiO4 were theoretically analyzed by density functional theory (DFT) calculations to investigate the typical two-peak emission of Sr2SiO4:Eu2+, which originates from two different Sr2+ (or Eu2+) sites in the Sr2SiO4 host structure. The Perdew-Wang generalized-gradient approximation (GGA) functional and the double numerical plus d-functions (DND) basis set with effective core potentials (ECP) were employed in the calculations of electronic properties. The electron transfer between Eu2+ ions placed at two different crystallographic Sr2+ sites was understood based on the accurate assignment of deconvoluted peaks of the two-peak emission to their corresponding crystallographic sites. This study ought to be instructive as a basic guideline to improve the color chromaticity of Sr2SiO4:Eu2+ for use in white light emitting diodes (WLEDs). 相似文献