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1.
A series of Gd11–xy Yb x Er y GeP3O26 germanate phosphates differing in the ratio of the Yb3+ and Er3+ active ions have been synthesized, and their luminescence spectra have been measured. According to X-ray diffraction characterization results, all of the synthesized germanate phosphates are single-phase and have a triclinic structure (sp. gr. P1). We have measured upconversion luminescence spectra due to the Er3+ 2H11/2, 4S3/24I15/2 and 4F9/24I15/2 radiative transitions in the synthesized gadolinium ytterbium erbium germanate phosphates and determined the luminescence upconversion energy yield (B en) in Gd11–xy Yb x Er y GeP3O26. The effects of the concentrations and ratio of the dopants in the Gd11(GeO4)(PO4)3O10 germanate phosphate host on B en and the ratio of the luminescence intensities in the red and green spectral regions (R/G) have been assessed.  相似文献   

2.
A series of In3+-doped Ba0.85Ca0.15TiO3:0.75%Er3+/xIn3+ (BCT:Er/xIn) lead-free piezoelectric ceramics with excellent upconversion luminescence were synthesized by the solid state reaction method. The effects of In3+ content on the crystal structure, ferroelectric, dielectric, piezoelectric, and upconversion luminescence properties were systematically studied. Under 980 nm excitation, a giant enhancement of the green emission (550 nm) by 10 times is achieved upon 2.5% mol In3+ doping, which is rarely observed in rare-earth ions-doped perovskite ferroelectric materials. The ultraviolet-visible-near infrared absorption measurements show that the In3+ doping may improve the dissolution of Er3+ ions and modify the isolate-/clustered-Er3+ ratio for x?≤?2.5%, resulting in the enhancement of the absorption cross-section, thereby contributing to the enhancement of green luminescence. Unfortunately, the In3+ doping suppresses the ferroelectric and piezoelectric properties of the BCT:Er/xIn ceramics. This problem can be resolved by adding a small amount (1 mol%) of Yb3+ to the BCT:Er/xIn ceramics to restore their good ferroelectric and piezoelectric properties. Such In3+ and rare-earth ions co-doped ceramics with greatly enhanced upconversion luminescence and good ferroelectricity and piezoelectricity may have potential applications in electro-optical devices.  相似文献   

3.
The photoluminescence (PL) spectra and Eu2+ excited state lifetime of EuGa2S4 and EuGa2S4:Er3+ have been studied in the range 78–500 K. The spectra show a band at 545 nm, due to the 4f 65d → 4f 7(8 S 7/2) transition. With increasing temperature, the full width at half maximum Γ(T) of the PL band of EuGa2S4 and EuGa2S4:Er3+ crystals increases from 0.15 to 0.22 and from 0.13 to 0.19 eV, respectively. Over the entire temperature range studied, Γ(T) is a linear function of T 1/2. The 545-nm emission intensity and Eu2+ excited state lifetime in EuGa2S4 and EuGa2S4:Er3+ vary exponentially with temperature. The luminescence quenching energies evaluated from the Arrhenius plots of I(103/T) and τ(103/T) coincide (0.10 eV) within the error of determination.  相似文献   

4.
Data are presented on the 300-K photoluminescence in GaS crystals doped with Er3+ or codoped with Er3+ and Yb3+. IR excitation (λex = 976 nm) gives rise to anti-Stokes luminescence in GaS:Er3+ (0.1 at %) and GaS:Er3+,Yb3+ (0.1 + 0.1 at %) and leads to an increased intensity of the emission due to the 4 I 11/24 I 15/2 transitions. The anti-Stokes luminescence is shown to result from consecutive absorption of two photons by one Er3+ ion, and the increased intensity of Er3+ luminescence in GaS: Er3+,Yb3+ is due to energy transfer from Yb3+ to Er3+.  相似文献   

5.
Novel green-emitting piezoelectric ceramics of SrBi4?x Er x Ti4O15 (SBT-xEr) were prepared. Strong up-conversion with bright green (524 and 548 nm) and a relatively weak red (660 nm) emission bands were obtained under 980 nm excitation at room temperature, which is attributed to the intra 4f–4f electronic transition of (2H11/2, 4S3/2)–4I15/2 and the transition from 4F9/2 to 4I15/2 of Er3+ ions, respectively. Simultaneously, Er3+ doping promotes the electrical properties. At 0.8 mol%Er, the optimal electric properties with high Curie temperature of T c?~527?°C, large remanent polarization of 2P r?~14.92 μC/cm2 and piezoelectric constant of d 33?~17 pC/N was achieved. As a multifunctional material, Er3+ doped SBT showed a great potential to be used in 3D-display, bio-imaging, solid state laser and optical temperature sensor.  相似文献   

6.
Bi2–хLaхFe4O9 and Bi2Fe4–2xTixCoxO9 ferrites have been prepared by solid-state reactions at a temperature of 1073 K. X-ray diffraction data indicate that, in the Bi2–хLaхFe4O9 system, the limiting degree of La3+ substitution for Bi3+ ions in Bi2Fe4O9 does not exceed 0.05 and that the limiting degree of substitution in the Bi2Fe4–2xTixCoxO9 system lies in the range 0.05 < x < 0.1. The specific magnetization and specific magnetic susceptibility of the samples have been measured at temperatures from 5 to 300 K in a magnetic field of 0.86 T. The field dependences of magnetization obtained for the Bi2–хLaхFe4O9 and Bi2Fe4–2xTixCoxO9 ferrites at temperatures of 300 and 5 K demonstrate that partial isovalent substitution of La3+ for Bi3+ ions in Bi2Fe4O9 and heterovalent substitution of Ti4+ and Co2+ ions for two Fe3+ ions leads to partial breakdown of the antiferromagnetic state and nucleation of a ferromagnetic state.  相似文献   

7.
Sm3+-activated NaSrPO4 phosphors could be efficiently excited at 403 nm, and exhibited a bright red emission mainly including four wavelength peaks of 565, 600, 646 and 710 nm. The highest emission intensity was found for NaSr 1?x PO4: xSm3+ with a composition of x = 0.007. Concentration quenching was observed as the composition of x exceeds 0.007. The decay time values of NaSr1?x PO 4 : xSm3+ phosphors range from around 2.55 to 3.49 ms. NaSr1?x PO4: xSm3+ phosphor shows a higher thermally stable luminescence and its thermal quenching temperature T 50 was found to be 350°C, which is higher than that of commercial YAG:Ce3+ phosphor and ZnS:(Al, Ag) phosphor. Because NaSr1?x PO4: xSm3+ phosphor features a high colour-rendering index and chemical stability, it is potentially useful as a new scintillation material for white light-emitting diodes.  相似文献   

8.
BaAl2O4:Eu2+,RE3+ (RE3+=Y, Pr) down conversion nanophosphors were prepared at 600 °C by a rapid gel combustion technique in presence of air using boron as flux and urea as a fuel. A comparative study of the prepared materials was carried out with and without the addition of boric acid. The boric acid was playing the important role of flux and reducer simultaneously. The peaks available in the XPS spectra of BaAl2O4:Eu2+ at 1126.5 and 1154.8 eV was ascribed to Eu2+(3d 5/2) and Eu2+(3d 3/2) respectively which confirmed the presence of Eu2+ ion in the prepared lattice. Morphology of phosphors was characterized by tunneling electron microscopy. XRD patterns revealed a dominant phase characteristics of hexagonal BaAl2O4 compound and the presence of dopants having unrecognizable effects on basic crystal structure of BaAl2O4. The addition of boric acid showed a remarkable change in luminescence properties and crystal size of nanophosphors. The emission spectra of phosphors had a broad band with maximum at 490–495 nm due to electron transition from 4f 65d 1 → 4f 7 of Eu2+ ion. The codoping of the rare earth (RE3+=Y, Pr) ions help in the enhancement of their luminescent properties. The prepared phosphors had brilliant optoelectronic properties that can be properly used for solid state display device applications.  相似文献   

9.
The article presents the formulas of quadrature frequency resolved spectroscopy (QFRS) on the upconversion photoluminescence (UCPL) of rare-earth (RE) doped materials on the general M-level model. The formulas are derived in matrix-equation form with the first-order perturbation on the rate equations at the M energy-levels of RE ion. The QFRS spectra for three different UCPL processes, i.e., the excited state absorption (ESA), energy transfer upconversion (ETU) and photon avalanche (PA) via cross relaxation process (CRP) in a particular case of M?=?3 are demonstrated with the respective salient features of the excitation power dependence. We have measured the QFRS on the UCPL (4 S 3/24 I 15/2) by systematically varying Er-doping in Ge28.1Ga6.3S65.6 chalcogenide glass from 0.01 to 0.5 at.% as well as 975 nm excitation power. Thereby the relaxation rates k 1 at the intermediate level 4 I 11/2, k 2 at the top level 4 S 3/2 and ETU parameter w are determined as a function of Er concentration. The UCPL dynamics on the basis of the formulas for the 3-level model is interpreted in terms of the determined parameters.  相似文献   

10.
Lead-free (K0.5Na0.5)(Nb1-xGe x )O3 (KNN-xGe, where x = 0-0.01) piezoelectric ceramics were prepared by conventional ceramic processing. The effects of Ge4+ cation doping on the phase compositions, microstructure and electrical properties of KNN ceramics were studied. SEM images show that Ge4+ cation doping improved the sintering and promoted the grain growth of the KNN ceramics. Dielectric and ferroelectric measurements proved that Ge4+ cations substituted Nb5+ ions as acceptors, and the Curie temperature (TC) shows an almost linear decrease with increasing the Ge4+ content. Combining this result with microstructure observations and electrical measurements, it is concluded that the optimal sintering temperature for KNN-xGe ceramics was 1020°C. Ge4+ doping less than 0.4 mol.%can improve the compositional homogeneity and piezoelectric properties of KNN ceramics. The KNN-xGe ceramics with x = 0.2% exhibited the best piezoelectric properties: piezoelectric constant d33 = 120 pC/N, planar electromechanical coupling coefficient kp = 34.7%, mechanical quality factor Qm = 130, and tanδ = 3.6%.  相似文献   

11.
A CsBaGd(MoO4)3:Er3+ phosphor with a scheelite-like structure (sp. gr. P21/n) has been synthesized and its luminescence properties have been studied. The synthesized material has been characterized by X-ray diffraction, differential thermal analysis, Raman spectroscopy, and IR spectroscopy.  相似文献   

12.
The effect of the synthesis conditions on the properties of inorganic laser-active liquids POCl3-SbCl5-235UO 2 2+ -Nd3+ is considered. The kinetic dependences of the U(IV) content and decay time of the Nd3+ luminescence in POCl3-SbCl5-235UO 2 2+ -Nd3+ solutions for various synthesis procedures at 380 K have been obtained. In POCl3-SbCl5-235UO 2 2+ -Nd3+ solutions, nonradiative energy transfer Nd3+ → U4+ is observed, and quenching of the Nd3+ luminescence is described by the Stern-Volmer law: k q = (6.4 ± 0.6) × 105 l mol?1 s?1. Laser liquids POCl3-SbCl5-235UO 2 2+ -Nd3+ with neodymium concentration of up to 0.7 M, uranyl concentration of up to 0.1 M, and decay time of the Nd3+ luminescence of up to 220 μs have been prepared for the first time.  相似文献   

13.
A series of Pr3+, Gd3+ and Pr3+–Gd3+-doped inorganic borate phosphors LiSr4(BO3)3 were successfully synthesized by a modified solid-state diffusion method. The crystal structures and the phase purities of samples were characterized by powder X-ray diffraction. Surface morphology of the sample was studied by scanning electronic microscopy (SEM). The optimal concentrations of dopant Gd3+ ions in compound LiSr4(BO3)3 were determined through the measurements of photoluminescence (PL) spectra of phosphors. Gd3+-doped phosphors LiSr4(BO3)3 show strong band absorption in UV spectral region and narrow-band UVB emission under the excitation of 276 nm was only due to 6P J 8S7/2 transition of Gd3+ ions. The effect of Pr3+ ion on excitation of LiSr4(BO3)3:Gd3+ was also studied. The excitation of LiSr4(BO3)3:Gd3+, Pr3+ gives a broad-band spectra, which show very good overlap with the Hg 253.7 nm line. The photoluminescence spectra of LiSr4(BO3)3 with different doping concentrations Pr3+ and keeping the concentration of Gd3+ constant at 0.03 mol have also been studied. The emission intensity of LiSr4(BO3)3:Pr3+–Gd3+ phosphors increases with increasing Pr3+ doping concentration and reaches a maximum at 0.01 mol. From the photoluminescence study of LiSr4(BO3)3:Gd3+, Pr3+ we conclude that there was efficient energy transfer from Pr3+→ Gd3+ ions in LiSr4?x?y Pr x Gd y (BO3)3 phosphors.  相似文献   

14.
The roentgenoluminescence spectra, temperature-dependent activator luminescence, optically stimulated luminescence, and the effect of IR irradiation on the yield and spectral composition of the low-temperature roentgenoluminescence and thermoluminescence curves of the Y3Al5O12:Ce3+ scintillator have been studied in the temperature range 85–295 K. The results, coupled with earlier data, suggest that the Ce3+ ions in the garnet crystal studied form Ce3+ p hole centers and increase the concentration of electronic F ?-centers responsible for the IR stimulation band at 940 nm. The reduction in roentgenoluminescence yield on cooling Y3Al5O12:Ce3+ to below 230 K is due to the significant localization of excited carriers at defects, which show up in thermoluminescence peaks and optical stimulation spectra. The low-temperature Ce3+ luminescence in Y3Al5O12:Ce3+ seems to result from the recombination of activator-bound excitons.  相似文献   

15.
The photoluminescence (PL) of Ga2S3-5 mol % Eu2O3 nanocrystals prepared by mechanical comminution of the initial compound has been studied in the temperature range from 77 to 300 K. It is established that the PL spectrum of nanocrystals, in comparison to that of a massive sample, extends over a broader wavelength interval (430–620 nm) and has two maxima (at 507 and 556 nm) instead of one. The intensity of emission from nanocrystals is significantly higher than that from the massive crystal. The halfwidth in both cases varies with the temperature in proportion to T 1/2. The intensity of emission at 556 nm for nanocrystals depends on the temperature as lgI ~ 1/T, this dependence having three linear portions corresponding to an activation energy of 0.04, 0.16, and 0.43 eV. The PL bands with maxima at 507 and 556 nm are assigned to the intracenter 4f 65d4f 7 transitions in Eu2+ ions.  相似文献   

16.
Polycrystalline sample LiMg(1?x)PO4:xTb3+ (x = 0.001, 0.002, 0.005, 0.01, 0.02) phosphor was synthesized via modified solid state method (MSSM). The prepared sample was characterized through XRD pattern (X-ray diffraction) and SEM (scanning electron microscope). Additionally, photoluminescence (PL), optically stimulated luminescence (OSL), thermoluminescence (TL) and other dosimetric properties including dose linearity, reusability and fading were studied. In OSL mode, sensitivity of prepared phosphor was found to be 2.7 times that of LiMgPO4:Tb3+, B (BARC) phosphor and 4.3 times that of α-Al2O3:C (BARC) phosphor. The TL glow consists of overlapping peaks in temperature range of 50–400°C and first peak (P1) was observed at 150°C, second peak (P2) at 238°C, third peak (P3) at 291°C and fourth peak (P4) at 356°C. The TL sensitivity of second peak (P2) of LiMgPO4:Tb3+ phosphor was compared with α-Al2O3:C (BARC) phosphor and found to be 100 times that of the α-Al2O3:C (BARC) phosphor. The minimum detectable dose (MDD) was found to be 5.6 μGy. Moreover, photoionization cross-sections, linearity, reusability, fading and kinetic parameters were calculated. Also, photoluminescence spectra of LiMgPO4: Tb3+ shows characteristic green–yellow emission exciting at 224 nm UV source.  相似文献   

17.
Single-phase ceramic samples of La1–xNdxInO3 (0.007 ≤ x ≤ 0.05), LaIn0.99M0.01O3, and La0.95Nd0.05In0.995M0.005O3 (M = Cr3+ and Mn3+) solid solutions have been prepared by solid-state reactions, and their crystal structure, magnetic field dependences of their specific magnetization at 5 and 300 K, and temperature dependences of their molar magnetic susceptibility have been studied. It has been shown that the 300-K specific magnetization of the La1–xNdxInO3 (x = 0.02, 0.05), La0.95Nd0.05In0.995M0.005O3 (M = Cr3+ and Mn3+), and LaIn0.99Mn0.01O3 solid solutions increases linearly with increasing magnetic field strength up to 14 T and that the magnitude of the 300-K specific magnetization of the La0.993Nd0.007InO3 and LaIn0.99Cr0.01O3 solid solutions increases linearly, but they have diamagnetic magnetization. At a temperature of 5 K, the magnetization of all the indates studied here increases nonlinearly with increasing magnetic field strength, gradually approaching magnetic saturation, without, however, reaching it in a magnetic field of 14 T. In the temperature range where the Curie–Weiss law is obeyed (5–30 K), the effective magnetic moments obtained for the Nd3+ ion (\({\mu _{effN{d^{3 + }}}}\)) in the La1–xNdxInO3 solid solutions with x = 0.007, 0.02, and 0.05 are 2.95μB, 3.09μB, and 2.75μB, respectively, which is well below the theoretical value \({\mu _{effN{d^{3 + }}}}\)= 3.62μB. The effective magnetic moments of the Cr3+ and Mn3+ ions in the LaIn0.99Cr0.01O3 and LaIn0.99Mn0.01O3 solid solutions are 3.87μB and 5.11μB, respectively, and differ only slightly from the theoretical values \({\mu _{effC{r^{3 + }}}}\)= 3.87μB and \({\mu _{effM{n^{3 + }}}}\)= 4.9μB.  相似文献   

18.
In this study, the luminescence performance of zinc phosphate glasses containing Eu3+ ion with the chemical compositions (60–x)NH4H2PO4-20ZnO-10BaF2-10NaF–x Eu2O3 (where x = 0.2, 0.5, 1.0 and 1.5 mol%) has been studied. These glasses were characterized by several spectroscopic techniques at room temperature. All the glasses showed relatively broad fluorescence excitation and luminescence spectra. Luminescence spectra of these glasses exhibit characteristic emission of Eu3+ ion with an intense and most prominent red emission (614 nm), which is attributed to 5D07F2 transition. Judd-Ofelt (Ω2, Ω4) parameters have been evaluated from the luminescence intensity ratios of 5D07FJ (where J = 2 and 4) to 5D07F1 transition. Using J-O parameters and excitation spectra, the radiative parameters are calculated for different Eu3+-doped glasses. Effect of γ-irradiation at fixed dose has been studied for all the Eu3+-doped glass matrices. The lifetimes of the excited level, 5D0, have been measured experimentally through decay profiles. The colour chromaticity coordinates are calculated and represented in the chromaticity diagram for Eu3+-doped zinc phosphate glasses for all concentrations.  相似文献   

19.
The compound (NH4)3[UO2(CH3COO)3]2(NCS) (I) was synthesized and examined by single crystal X-ray diffraction analysis. The compound crystallizes in the rhombic system with the unit cell parameters a = 11.5546(4), b = 18.5548(7), c = 6.7222(3) Å, V = 1441.19(10) Å3, space group P21212, Z = 2, R = 0.0345. The uranium-containing structural units of crystals of I are isolated mononuclear groups [UO2(CH3COO)3]? belonging to crystal-chemical group AB 3 01 (A = UO 2 2+ , B01 = CH3COO?) of uranyl complexes. The specific features of packing of the uranium-containing complexes in the crystal structure are considered.  相似文献   

20.
The crystal structure of a previously unknown compound [CH3NH3][(UO2)(H2AsO4)3] was solved by direct methods and refined to R 1 = 0.038 for 3041 reflections with |F hkl | >-4σ |F hkl |. The compound crystallizes in the monoclinic system, space group P21/c, a = 8.980(1), b = 21.767(2), c = 7.867(1) Å, β = 115.919(5)°, V = 1383.1(3) Å3, Z = 4. In the structure of the compound, pentagonal bipyramids of uranyl ions, sharing bridging atoms with tetrahedral [H2AsO4]? anions, form strongly corrugated layered complexes [(UO2)(H2AsO4)3]? arranged parallel to the (100) plane. The protonated methylamine molecules [CH3NH3]+ form unidimensional tapelike packings parallel to the c axis and linked by hydrophilic-hydro-phobic interactions. The topology of the layered uranyl arsenate complex [(UO2)(H2AsO4)3]? is unusual for uranyl compounds and was not observed previously. A specific feature of this topology is the presence of monodentate arsenate “branches” arranged within the layer.  相似文献   

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