Reaction Method In Air Atmosphere Research Articles

The effects of Lu3+, Gd3+ and Ga3+ substitution on the photoluminescence of Y2.95-x-yLuxGdyAlzGa5-zO12:0.05Ce3+ phosphors for high-power white AC-LEDs.

Various yellowish-green persistent phosphors of Y2.95-x-yLuxGdyAl5-zGazO12:0.05Ce3+ (x = 0-1, y = 0-1, z = 1-4) were successfully synthesized by the one-step high-temperature solid-state reaction method in air. The effects of simultaneous doping of Lu3+, Gd3+ and Ga3+ on the luminescence properties of the phosphors were investigated in detail for the first time. Herein, the microstructure, morphology, afterglow performance, luminescence properties, thermoluminescence, thermal quenching and flicker index of the efficient blue-light-activated Y2.95-x-yLuxGdyAl5-zGazO12:0.05Ce3+ phosphors were tested. The τ90 and τ80 values of Y1.45LuGd0.5Al2.5Ga2.5O12:0.05Ce3+ are 10.8 ms and 33.2 ms, respectively. These parameters are important in terms of effectiveness in reducing flicker in alternating current (AC) LEDs. Compared with the conventional Y3Al2Ga3O12:Ce3+ phosphor, the Y1.45LuGd0.5Al2.5Ga2.5O12:0.05Ce3+ phosphor has a better luminescence performance, stronger afterglow performance, and lower flicker index. The quantum yield of the Y1.45LuGd0.5Al2.5Ga2.5O12:0.05Ce3+ phosphor was 86.42% and the luminous efficiency of the LED devices prepared with it reached 92.12 lm W-1 when operated at 100 mA. Integrating sphere and spectroradiometer tests as well as CIE chromaticity diagrams indicate that the AC-WLEDs assembled by mixing the Y1.45LuGd0.5Al2.5Ga2.5O12:0.05Ce3+ phosphor and a commercial red phosphor in an appropriate ratio could obtain ideal white light with a high color-rendering index (87.9) and the flickering index was successfully reduced from 100% to 61.4%.

Photoluminescence properties of Eu-doped WO3-Eu2(WO4)3 composites and single-phase Eu2(WO4)3 powders

The development of highly stable and efficient oxide-based red phosphors is urgently required for next-generation lighting devices. Herein, we report the micro/crystal structures and luminescent properties of single-phase Eu2(WO4)3 and Eu3+-doped WO3-Eu2(WO4)3 composite phosphors prepared by a one-step conventional solid-state reaction method in air atmosphere. As increasing Eu contents in the mixtures of WO3 and Eu2O3, the intensities of the X-ray diffraction peaks of Eu2(WO4)3 increased while that of WO3 decreased. The photoluminescence intensity of the synthesized phosphors increased with increase in the Eu content when calcined at 900 °C, while it degraded at a higher temperature. Red-emitting single-phase Eu2(WO4)3 powders were successfully obtained when the WO3 and Eu2O3 powders were calcined in the ratio of 3:1. The intensity of the red emission spectra of the Eu2(WO4)3 phosphor was higher than those of the 6, 12, and 24 at.% Eu-added WO3 composites at excitation wavelengths of 394 and 465 nm. On the other hand, the intensity of emission from the single-phase phosphor was lower than that of the Eu-doped WO3-Eu2(WO4)3 composites under excitation of UV light at 254 nm. Thus, we propose two prospective phosphors for application as red phosphors at various wavelengths.

Evaluation of trapping parameters of europium doped tristrontium dialuminium oxide phosphor by different thermoluminescent analysis methods

In the present work, we have synthesized Europium (Eu) doped Tristrontium Dialuminium Oxide (Sr3Al2O6:Eu) phosphor by solid state reaction method in air atmosphere. The thermoluminescence (TL) properties of the synthesized phosphor are investigated and presented. Theoretical analysis of glow curves of Sr3Al2O6:Eu was done by computerized glow curve deconvolution (GCD) method, and the trapping parameters of the synthesized phosphor, such as activation energy, frequency factor, order of kinetics, etc. are discussed and explained. These trapping parameters are determined by different methods, such as Chen’s peak shape method, initial rise method, and Ilich method. The synthesized phosphor is found to be a good candidate for dosimetric applications.

Enhanced luminescence properties of Eu3+ in La2MoO6 by nonsensitization of Bi3+

AbstractIt was unusual for Bi3+ ions to enhance the emission intensity of phosphors via nonsensitization. Here, La2MoO6:Eu3+, Bi3+ phosphors were successfully synthesized by a high temperature solid‐state reaction method in air atmosphere. As the increase of doping concentration of Bi3+, the emission spectra of La2MoO6:Eu3+, Bi3+ phosphors had obvious shifts, splits and the enhancement of intensities, which indicated that the characteristics of the phosphors were modified. To analyze these phenomena, the crystal structure refinements, spectral characteristic analyze and Judd‐Ofelt theoretical calculation were mainly performed. Bi3+ ions played the role of the nonsensitizer and affected the distortion of the crystal, the sites of Eu3+ ions, the field splitting energy and the internal quantum yield. Moreover the nephelauxetic effects of Bi3+ ions and the ET process caused synergistically the life times of La2MoO6:Eu3+, Bi3+ phosphors to increase and then gradually decrease. The CIE coordinates of phosphors changed within a small range. This study might be instrumental in promoting the further application of Bi3+ ions in rare earth luminescent materials.

Synthesis and luminescence properties of LiBaB9O15:Eu3+ single-component red-light emitting phosphors

The borate phosphors LiBaB9O15:Eu3+ were successfully synthesized by high temperature solid-state reaction method in air atmosphere. The formation of single phase samples was confirmed by powder X-ray diffraction, the luminescence properties of phosphors were characterized by fluorescence spectroscopy and chromaticity coordinates. X-ray diffraction results demonstrate that single-phase LiBaB9O15 was formed when sintered at 700 °C for 1 h. The effect of the excess amount of H3BO3 and Eu3+ doping concentration on the photoluminescence properties of LiBaB9O15:Eu3+ were investigated. The excitation and emission spectra indicate that the prepared phosphors can be effectively excited by UV and n-UV light and exhibit a strong red emission of Eu3+ (5D0→7F2 transition) at 612 nm. Phosphors with 15% excess of H3BO3 and Eu3+ doping concentration 0.59 have stronger luminescence intensity. According to Dexter theory, the concentration quenching mechanism was multipole-multipole interaction. The CIE chromaticity coordinates of LiBaB9O15:0.59Eu3+ phosphor (0.6415, 0.3411) was closer to the standard red-light CIE coordinates (0.67, 0.33). The luminescence properties of the commercial Y2O3:Eu3+ phosphor and the prepared LiBaB9O15:0.59Eu3+ phosphor were compared, the emission intensity of LiBaB9O15:0.59Eu3+ phosphor was weaker than Y2O3:Eu3+ phosphor under excitation of 260 nm wavelength, stronger than Y2O3:Eu3+ phosphor under excitation of 362 nm and 394 nm wavelength.

Tunning of photoluminescence emission of Y2SiO5:Tb3+, Eu3+ phosphors by altering the Tb3+, Eu3+ ratio

The Y2SiO5:Tb3+, Eu3+ phosphors were synthesized by a high temperature solid-state reaction method in air atmosphere and their crystal structures, lifetime, luminescence properties, and energy transfer mechanism were investigated in detail. A series of characteristic emissions of phosphors were observed in the emission spectra at around 545 nm, 593 nm, and 613 nm when excited at 350 nm. The energy-transfer mechanism from Tb3+ to Eu3+ in Y2SiO5 is determined by a dipole–dipole interaction. The CIE coordinates of the phosphors can be tuned from blue-green through white, to yellow and finally to orange-red with changing the Eu3+/Tb3+ ratio. The average decay time of Eu3+ increases from 2.10 to 5.81 ms with the concentration of Tb3+ increasing from 2% to 8%, and reaches the maximum at 0.08, and is shortened when the concentration of Tb3+ goes beyond 8%.

Synthesis and red emitting properties of NaAlP2O7:Pr3+ polycrystal for blue chip-excited WLEDS

Abstract A series of NaAlP2O7:xPr3+ (x = 1, 3, 5, 7, 9, 11, 13%) polycrystals have been prepared using the high temperature solid-state reaction method in air atmosphere. X-ray diffraction (XRD) measurements disclosed that all Pr3+ doped samples are single phase with the crystal structure of diphosphate NaAlP2O7 host. The fourier transform infrared (FT-IR) spectrum, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectrometry as well as photoluminescence excitation (PLE) and photoluminescence (PL) measurements were carried out at room temperature. NaAlP2O7:Pr3+ polycrystal exhibits a red emission with dominant peak at 663 nm under the visible blue light irradiation. The optimum dopant concentration of Pr3+ is 9%. The concentration quenching mechanism, CIE chromaticity coordinate and IQE were also present in this paper. This work reveals that NaAlP2O7:Pr3+ polycrystal is a potential red emitting phosphor for blue chips-excitated WLEDS.

Blue emission of Co2+ in K2ZnP2O7 phosphors

K2ZnP2O7: Co2+ blue emitting phosphors have been successfully synthesized by the solid state reaction method in air atmosphere. The X-ray diffraction (XRD) indicated that the samples crystallize in P42/mnm tetragonal space group. The photoluminescence properties were investigated. The excitation and emission band peaking at 272 nm and 386 nm respectively for K2ZnP2O7:0.01Co2+ phosphor, and the CIE color coordinate values were (x = 0.156, y = 0.073) indicated that the emitting color is blue. The correlated color temperature is calculated. The K2ZnP2O7: xCo2+ phosphors can be used for the white-light LEDs.

Luminescence properties of Cr3+ ions in Na2ZnP2O7 crystal

A green emitting phosphors have been successfully synthesized of Na2ZnP2O7 (NZPO) doped by chrome (Cr3+) using a solid state reaction method in air atmosphere for different Cr3+ concentrations (1, 1.25, 1.5, 1.75, 2 and 2.25 mol %). The synthesized samples were characterized by X-ray diffraction (XRD) which indicated that the Na2ZnP2O7: Cr3+ phases crystallize in P42/mnm tetragonal space group. Photoluminescence properties were investigated. The emission band is found to be centred at 527 nm under 417 nm excitation wavelength. The CIE chromaticity coordinates and the correlated color temperature (CCT) are both addressed. The information derived from the present study may be useful for white-LEDs.

Break the Interacting Bridge between Eu3+ Ions in the 3D Network Structure of CdMoO4: Eu3+ Bright Red Emission Phosphor

Eu3+ doped CdMoO4 super red emission phosphors with charge compensation were prepared by the traditional high temperature solid-state reaction method in air atmosphere. The interrelationships between photoluminescence properties and crystalline environments were investigated in detail. The 3D network structure which composed by CdO8 and MoO4 polyhedra can collect and efficiently transmit energy to Eu3+ luminescent centers. The relative distance between Eu3+ ions decreased and energy interaction increased sharply with the appearance of interstitial occupation of O2− ions ({O^{primeprime} }_{i}). Therefore, fluorescence quenching occurs at the low concentration of Eu3+ ions in the 3D network structure. Fortunately, the charge compensator will reduce the concentration of {O^{primeprime} }_{i} which can break the energetic interaction between Eu3+ ions. The mechanism of different charge compensators has been studied in detail. The strong excitation band situated at ultraviolet and near-ultraviolet region makes it a potential red phosphor candidate for n-UV based LED.

Crystal structure, electronic structure and photoluminescence properties of KLaMgWO6:Eu3+ phosphors

A variety of Eu3+-activated KLaMgWO6 phosphors were synthesized by a traditional high temperature solid state reaction method in air atmosphere. By using geometric optimization and Rietveld analysis, the detailed structural properties were derived for the first time. The band structure, electronic distribution and phonon dispersion were calculated using the plane-wave density functional theory (DFT). Meanwhile, the optical band gap of KLaMgWO6 host was measured with an ultraviolet-visible diffuse reflection spectroscopy (UV–vis DRS). The charge transfer band (CTB) of KLaMgWO6:Eu3+ phosphors is situated at ultraviolet and near-ultraviolet region from 250 to 410 nm. Combined with theoretical calculations and experimental results, the detailed luminescence process is deduced. The phosphors show intense absorption in near ultraviolet-blue region and exhibit strong red emissions with CIE coordinates of (x = 0.6474, y = 0.3360) under 344 and 394 nm excitation. Excellent luminescence properties make it have potential application in the fabrication of white light-emitting diodes (LEDs).

Synthesis, characterization and mechanoluminescence properties of europium doped (1-x) MgO.xBaO-Al2O3:0.1 Eu (x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, and 1.0) phosphor

A series of phosphor sample powders with varying concentrations of Magnesium and Barium concentration were prepared by high temperature solid state reaction method in air atmosphere. The phase formation of the calcined samples were confirmed by taking powder XRD and particle size of the sample powders were identified using SEM picture. The mechanoluminescent (ML) studies of each sample in the series were carried out via impact method. Variations in mechanoluminescence intensities were observed due to the variations in percentage compositions of magnesium and barium in the powder phosphors. The role of barium as sensitizer for enhancing ML intensities was undoubtfully proved and effort was taken to investigate about optimum concentration of barium for observing highest ML activity. The significant variations observed in ML intensities with stress variations and large decay time indicates the future scope of the sample for stress sensing applications. The Photoluminescence (PL) of the samples was studied using PL spectrum. The appreciable value of decay time and significant ML intensity variations of the sample with change in impact velocities highlights the future scope of the phosphor for stress sensing applications.

Luminescence properties and crystal structure of Sr3Sc(PO4)3:Sm3+ as novel orange-red emitting phosphors

A series of novel orange-red-emitting phosphors Sr3Sc1-x(PO4)3:xSm3+ was synthesized by high-temperature solid-state reaction method in air atmosphere. The crystal structure, photoluminescence and decay properties of the phosphors were investigated in detail for their applications in white light-emitting diodes. Phase results demonstrated that Sr3Sc1-x(PO4)3:xSm3+ crystallized in a cubic crystal system and the phase structure was represented. The emission spectra of Sr3Sc1-x(PO4)3:xSm3+ samples were composed of four sharp peaks around 566, 603, 649, and 711nm, respectively. The optimum doping concentration of Sm3+ ions and the mechanism of energy transfer among Sm3+ were also discussed in detail. Sr3Sc0.94(PO4)3:0.06Sm3+ exhibited excellent thermal stability. All the obtained results show that the Sr3Sc1-x(PO4)3:xSm3+ phosphors have considerable potential as orange-red phosphors for applications in the near ultraviolet excited white light emitting diodes.

Luminescence properties and energy transfer in Tb3+ and Eu3+ co-doped Ba2P2O7 phosphors

The Ba2P2O7:Tb3+, Eu3+ phosphors were synthesized by a high temperature solid-state reaction method in air atmosphere and their crystal structures, lifetime, luminescence properties, and energy transfer mechanism were investigated in detail.

Effect of excess TiO2 addition on the PTC properties of Ba0.99Y0.01TiO3-0.001MnO based ceramics

BaTiO3 is a typical ceramic with a positive temperature coefficient of resistivity (PTC). The grain conductivity of BaTiO3 is associated with doping, and the grain boundary plays an important role in the PTC effect. In this study, Ba0.99Y0.01TiO3-0.001MnO-xTiO2 (x=0.01–0.07) ceramics were synthesized by the conventional solid-state reaction method in air atmosphere. The influence of excess TiO2 on the crystal structure, microstructure, binding energy and the PTC characteristics were investigated by XRD, SEM, EDS, XPS and impedance spectroscopy, respectively. The results showed that excellent room-temperature resistivity and resistance jump ratio (Rmax/Rmin) up to 84Ωcm and 1.6×105 could be obtained possibly associated with the two different roles played by Ti ions at the grain boundaries.

Photoluminescence characteristics of a novel red phosphor Ba2Si4O10: Eu3+: structural effect and concentration quenching mechanism

A novel red phosphor Ba2Si4O10: Eu3+ was synthesized by the high-temperature solid state reaction method in air atmosphere. The crystal results reveal that Ba2Si4O10 has two different phases, in which the high-temperature phase belongs to monoclinic system and exhibits better photoluminescence property compared with low-temperature phase. The monoclinic Ba2Si4O10 was obtained at 1250°C and matched well with the JCPDS Card No. 83-1446. Photoluminescence excitation and emission spectra, fluorescence lifetime and quantum yield are conducted to investigate the luminescent property of Ba2Si4O10: Eu3+ phosphor. The results show that the phosphor can be excited by 393nm light (7F0→5L6) effectively and emit a strong red emission at 612nm (5D0→7F2). The optimal concentration of Eu3+ ions in Ba2Si4O10 matrix is 0.02, where the fluorescence lifetime was 1.0837 ms and the quantum yield was up to 31.64%. Additionally, the chromaticity coordinates of the optimal composition Ba1.98Si4O10: 0.02Eu3+ phosphor is calculated to be (0.65, 0.34). These results suggest that Ba2Si4O10: Eu3+ phosphor could be a potential red phosphor for practical application and optical devices.

Luminescence properties and energy transfer in Dy3+ and Eu3+ co-doped Sr3Y(PO4)3 phosphor

The phosphors Sr3Y(PO4)3: Dy3+, Eu3+ were synthesized by a high temperature solid-state reaction method in air atmosphere and their crystal structures, luminescence properties, lifetime, and energy transfer mechanism were investigated in detail. The co-doped Dy3+ and Eu3+ in Sr3Y(PO4)3 could enhance emission of Eu3+ ions and a series of characteristic emissions of Dy3+ and Eu3+ were observed in the emission spectra at around 487 nm, 575 nm, and 615 nm when excited at 350 nm. It indicates that the energy transfer occurs from Dy3+ to Eu3+ and the intensity ratio of multicolor emission could be tuned by adjusting their concentration ratio on the basis of efficient Dy3+ – Eu3+ energy transfer. The energy-transfer mechanism from Dy3+ to Eu3+ in Sr3Y(PO4)3 is determined to be a quadrupole-quadrupole interaction and the critical distance between Dy3+ and Eu3+ is 15.22 Å. The decay life time of the Dy3+ ions decreases with the increase of the Eu3+ dosage concentration.

Preparation and piezoelectric properties of CuO-added (Ag0.75Li0.1Na0.1K0.05)NbO3 lead-free ceramics

CuO-doped (Ag0.75Li0.1Na0.1K0.05)NbO3 (ALNKN-xCuO, x = 0–2mol%) lead-free piezoelectric ceramics were prepared by the solid-state reaction method in air atmosphere. The effects of CuO addition on the phase structure, microstructure, and piezoelectric properties of the ceramics were investigated. The experimental results show that the ALNKN ceramics without doping CuO possess rhombohedral phase along with K2Nb6O16-type phase and metallic silver phase. For all of the CuO-doped ALNKN ceramics, a pure perovskite structure with the orthorhombic phase was obtained by enclosing the samples in a corundum tube. A homogeneous microstructure with the grain size of about 1 μm was formed for the ceramics with 0.5mol% CuO. The grain size increases with increasing amount of CuO. The temperature dependence of dielectric properties indicates that the ferroelectric phase of the ALNKN-xCuO ceramics becomes less stable with the addition of CuO. The ceramics with x = 1mol% exhibit relatively good electrical properties along with a high Curie temperature. These results will provide a helpful guidance to preparing other AN-based ceramics by solid-state reaction method in air atmosphere.

Synthesis, photoluminescence and Judd–Ofelt parameters of LiNa3P2O7:Eu3+ orthorhombic microstructures

We report, for the first time, the photoluminescence properties of Eu3+-doped LiNa3P2O7 phosphor, synthesized by a facile solid-state reaction method in air atmosphere. The crystal structure and phase purity of the phosphors were analyzed by X-ray diffraction analysis. Orthorhombic structural morphology was identified by scanning electron microscopy. The phosphate groups in the phosphor were confirmed by Fourier transform infrared analysis. Bandgap of the phosphor was calculated from the diffuse reflectance spectra data using Kubelka–Munk function. Under 395-nm UV excitation, the phosphors show signs of emitting red color due to the 5D0 → 7F2 transition. In accordance with Judd–Ofelt theory, spectroscopic parameters such as oscillator intensity parameter Ω t (t = 2), spontaneous emission probabilities, fluorescence branching ratios and radiative lifetimes were calculated and analyzed for the first time in this system.

Tuning the Color Emission of Sr2P2O7: Tb3+, Eu3+ Phosphors Based on Energy Transfer

A series of color tunable Tb3+‐ and Eu3+‐activated Sr2P2O7 phosphors were synthesized by a traditional solid‐state reaction method in air atmosphere. The crystal structure, photoluminescence (PL) properties, energy transfer, thermal stability, and luminous efficiency were investigated. A series of characteristic emission of Tb3+ and Eu3+ were observed in the PL spectra and the variation in the emission intensities of the three emission peaks at around 416 nm (blue), 545 nm (green), and 593 nm (orange‐red) induced the multicolor emission evolution by tuning the Tb3+/Eu3+ content ratio. The energy‐transfer mechanism from Tb3+ to Eu3+ ion was determined to be dipole–dipole interaction, and the energy‐transfer efficiency was about 90%. The novel phosphors have excellent thermal stability in the temperature range of 77–473 K and the Commission International De L'Eclairage 1931 chromaticity coordinates of Sr2P2O7: Tb3+, Eu3+ (λex = 378 nm) move toward the ideal white light coordinates.