Novel Tb³âº-Doped LaAl2B4O10 phosphors: Structural analysis, luminescent properties, and energy transfer mechanism.

This study explores the structural and luminescent properties of terbium (Tb³âº)-doped lanthanum aluminium borate (LaAl2B4O10, abbreviated as LAB) phosphors, a novel host lattice for Tb³âº doping. LAB:Tb³âº phosphors, with varying dopant concentrations, were synthesized using a microwave-assisted combustion synthesis approach and characterized using X-ray diffraction (XRD), Rietveld refinement, and photoluminescence spectroscopy at both room and low temperatures. The structural analysis confirmed the hexagonal crystal structure of LAB and revealed successful incorporation of Tb³âº ions without altering the fundamental lattice. Luminescence studies demonstrated that the LAB:Tb³âº phosphors show strong green emission primarily attributed to the 5D4→7F5 transition of Tb³âº. The optimal doping concentration was determined to be 5 wt% Tb³âº, which provided maximum luminescence efficiency. This concentration also allowed for a critical study of energy transfer mechanisms within the phosphor, revealing dipole-dipole interactions with a critical distance of 9.80 Å between Tb³âº ions. Additionally, the CIE chromaticity coordinates of LAB:0.05 Tb³âº were precisely determined to be (0.289, 0.4460), indicating the potential for high-quality green emission suitable for solid-state lighting and display technologies. This work not only demonstrates the potential of LAB:Tb3+ as a highly efficient green luminescent material, but also sheds light on the mechanisms responsible for energy transfer and concentration quenching.

Synthesis and photoluminescence characteristics of a novel Eu and Tb doped Li2MoO4 phosphor.

Li2MoO4:x Eu3+ and Li2MoO4:xTb3+ phosphors, where x = 0.5, 1, 2, 3, 5 and 7 wt%, were synthesized through a gel-combustion method. The XRD data reveals that Eu3+ and Tb3+ doped Li2MoO4 phosphors exhibit a Rhombohedral structure belonging to the space group R3 which matched well with the standard JCPDS files (No.012-0763). We present photoluminescence (PL) spectra from Eu and Tb doped Li2MoO4 under 349 nm Nd:YLF pulses laser excitation over the temperature range of 10-300 K. Undoped Li2MoO4 shows a wide broad band around 600 nm because of the intrinsic PL emission of tetrahedral of MoO42- which was in good agreement with previous findings. Under the excitation of 394 nm, the as-synthesized phosphors exhibited sharp and strong intensity PL emission signals in the red (612 nm, 5D0→7F2 transition) and green (544 nm, 5D4→7F5 transition), respectively. The critical doping concentration of Eu3+ and Tb3+ ions in the Li2MoO4 were estimated to be 2 wt%. The concentration quenching phenomena were discussed, and the critical distances for energy transfer have also been evaluated by the concentration quenching.

Synthesis and photoluminescence characteristics of Dy incorporated MoO3 phosphor: Suppression concentration quenching.

A series of MoO3:Dy3+ phosphors have been synthesized via the gel-combustion method. The X-ray and photoluminescence (PL) emission spectra were employed to characterize the obtained phosphors. The prepared samples were characterized through XRD measurements and exhibited that Dy3+ ions can be successfully incorporated into the host material. The PL emission bands of Dy3+ doped MoO3 were observed at 486 nm, 574 nm and 666 nm which are assigned to the transitions of 4F9/2 â†’ 6H15/2, 4F9/2 â†’ 6H13/2 and 4F9/2 â†’ 6H11/2, respectively. Concentration quenching were largely taken into consideration as one of the crucial aspects limiting the application range of phosphors in today's modern world. An abnormal thermal quenching dependence was reported when Dy3+ ions were incorporated into MoO3 host matrix. In order to understand the origin of this beneficial behaviour, energy transfer processes occurring via radiative and nonradiative mechanisms were investigated to elucidate this suppression of the concentration quenching.

Structural and spectroscopic properties of LaAlBO3 doped with Eu3+ ions.

In this study, we performed X-ray diffraction (XRD) and environmental scanning electron microscope (ESEM) techniques to examine the structure and morphological observation of the samples and thermoluminescence (TL) experiments to extract the trapping parameters and dosimetric properties of LaAlBO3 phosphors doped with Eu at various doping concentrations. Diffraction patterns of obtained sample were well consistent JCPDS card No 98-009-7945, indicating the formation of pure phase. The TL kinetic parameters were estimated by CGCD software. TL glow curves of LaAlBO3:Eu3+ consist of 12 trap levels and exhibited dominantly first order kinetics. Photoluminescence (PL) emission was observed in the range 400-800 nm for LaAlBO3 phosphor doped with Eu3+. The dominant emission of Eu3+ corresponding to the electric dipole transition 5D0 → 7F2 is located at 616 nm. The sharp emission properties exhibited demonstrate that the LaAlBO3 is a suitable host for rare-earth ion doped phosphor material. It is observed that for the variable concentration of Eu3+ on PL studies, the PL intensity augments with increase in the dopant concentration and the concentration quenching was found after 1 mass% of Eu3+. The PL experimental results reveal that LaAlBO3:Eu3+ phosphor as an red emitting phosphor may be promising luminescence materials for the optoelectronic applications.

Preparation and cathodoluminescence characteristics of rare earth activated BaAl2O4 phosphors.

Undoped and Pr, Sm and Tb activated BaAl2O4 phosphors have been synthesized by solid state reaction method and combustion method. The structure and morphological observation of the phosphor samples were monitored by X-ray powder diffraction (XRD) and environmental scanning electron microscope (ESEM) coupled to an energy dispersive X-ray spectrometer (EDS). The all diffraction peaks are well assigned to standard data card (PDF♯17-306). Emission properties of the samples were explored using light emission induced by an electron beam (i.e cathodoluminescence, CL) at room temperature (RT). Undoped BaAl2O4 sample exhibits a broad defect emission from 300 to 500 nm from the aluminate defect centres. CL spectra recorded at room temperature display that the as-prepared BaAl2O4:Ln (Ln=Pr, Sm and Tb) phosphors exhibit different luminescence colors coming from different rare earth activator ions. The transition 4G5/2 → 6H7/2 located at 606 and 610 nm for Sm3+ can occur as hypersensitive transition having the selection rule ΔJ = ±â€¯1. For the Tb3+ doped samples, they exhibit D45 green line emissions. The proposed luminescent mechanisms of all doped rare earth ions are also discussed.

Luminescence studies of zinc borates activated with different concentrations of Ce and La under x-ray and electron excitation.

Several ZnB2O4 powder samples having dopants concentrations of 0.1, 0.01, 0.04wt% Ce and La were prepared using the nitric acid method via the starting oxides. Several complementary methods such as powder X-ray diffraction (XRD), thermal analyses environmental scanning electron microscopy (ESEM), Radioluminescence (RL) and Cathodoluminescence (CL) techniques were used. Unique luminescence properties of Ce doped ZnB2O4 powder samples are reported for the first time. A new luminescence bands appearing in red part of the spectrum and having all the characteristics of Ce3+ were obtained from RL results. Changing the Ce and La concentration of 0.01-0.1wt% leads to an increase in RL and CL intensities of Ce3+ and La3+ ions and also CL emission spectra of ZnB2O4 show gradual shift towards longer wavelength. When we compare the luminescence intensity of the samples it is seen that Ce doped ZnB2O4 has the highest intense whereas La doped ZnB2O4 has the lowest one. However, emission spectra of both Ce and La doped samples kept unchanged.

Optical spectroscopy of the Ce-doped multicomponent garnets.

Here, we report our results referring to the preparation of Ce doped Y2.22MgGa2Al2SiO12, Y1.93MgAl4SiO12 and Y2.22Gd0.75Ga2Al3O12 using solid state reaction at high temperature. Several complementary methods (i.e. powder x-ray diffraction (XRPD), energy dispersive analysis of X-rays (EDX), scanning electron microscopy (SEM) and Fourier transforms infrared spectroscopy (FTIR)) were studied to examine the effects of the synthesis procedure on the morphology and structure. XRD analyses revealed that all compounds include yttrium aluminate phase with garnet structure. Cathodoluminescence (CL), radioluminescence (RL) and photoluminescence (PL) measurements were carried out for clarification of relationship between host lattice defects and the spectral luminescence emissions. Luminescence emission of phosphors is peaked at 530nm assigned to 5d-4f transitions of the dopant Ce(3+) ions with a broad emission band in 400-700nm range. Under electron irradiation, the emission spectrum of Ce doped (YGd)3Ga2Al3O12 is well defined and has a characteristic fairly narrow and sharp emission band peaking at 312nm and 624nm corresponding to transition of (6)P7/2 →(8)S7/2 and (6)GJ→(6)PJ (Gd(3+)), respectively. We suggest some of phosphors might be excellent phototherapy phosphor materials under electron excitation.

Thermoluminescence studies of Nd doped Bi4Ge3O12 crystals irradiated by UV and beta sources.

Thermoluminescence (TL) glow curves of pure and rare earth doped bismuth germanate (BGO) were investigated under UV and beta radiation. The glow curves of pure BGO crystal present different patterns for both kinds of radiation. The TL glow curves of BGO crystals doped with Nd ions are similar to that of pure BGO under UV radiation. The kinetic parameters, kinetic order (b), activation energy (E) and frequency factor (s) of the TL glow curves of pure BGO crystal have been determined by peak shape method. Activation energies of 3 peaks obtained by PS were found to be 1.81, 1.15 and 1.78, respectively.

Visible to infrared low temperature photoluminescence of rare earth doped bismuth germanate crystals.

In this paper, the influence of a series of rare earth (Eu, Tm, Nd) and Cr ion doping on the optical properties of BGO was investigated by means of photoluminescence (PL) from visible to IR region in the 10-300K temperature range using different types of detectors, namely, photomultiplier tube (PMT), InGaAs (IGA), and Si. Several samples were investigated having dopants concentrations of 0.3wt%Nd, 0.4wt%Tm, 0.06wt% Cr and 3ppm Eu. The PL spectra of the samples showed different luminescence behaviour which is assigned to the 4f intra shell transition from rare earth ions. The temperature dependence of the PL from rare earth doped BGO crystals is also examined.

Characterisation and luminescence studies of Tm and Na doped magnesium borate phosphors.

In this study, structural and luminescence properties of magnesium borate of the form MgB4O7 doped with Tm and Na were investigated by X-ray diffraction (XRD), Raman spectroscopy and cathodoluminescence (CL). The morphologies of the synthetised compounds exhibit clustered granules and road-like materials. As doping trivalent ions into a host with divalent cations requires charge compensation, this effect is discussed. The CL spectra of undoped MgB4O7 shows a broad band emission centred around 350 nm which is postulated to be produced by self-trapped excitons and some other defects. From the CL emission spectrum, main emission bands centred at 360, 455, 475 nm due to the respective transitions of (1)D2→(3)H6,(1)D2→(3)F4 and (1)G4→(3)H6 suggest the presence of Tm(3+) ion in MgB4O7 lattice site. CL mechanism was proposed to explain the observed phenomena which are valuable in possibility of the developing new luminescent materials for different applications. In addition, the experimental Raman spectrum of doped and undoped MgB4O7 were reported and discussed.

Visible to infrared low temperature luminescence of Er(3+), Nd(3+) and Sm(3+) in CaSnO3 phosphors.

Novel stannate phosphor, orthorhombic CaSnO3 phosphors doped with Er(3+), Nd(3+) and Sm(3+) have been synthesized by a conventional solid-state method under N2+H2 gas flow. Visible and near-infrared photoluminescence (PL) properties were investigated as function of laser power and temperature. It was observed that all dopant ions are well incorporated in CaSnO3 and are responsible for the optical emission in the temperature range of 10-300K. PL peaks at 490, 546, 656, 696, 894, 1065, and 1344nm were observed for the CaSnO3:Nd(3+) phosphor and associated to f-f transition of Nd(3+) ion. Emissions at 564, 600-607, 646-656 and 714nm were detected for the CaSnO3:Sm(3+). The strongest one, observed at 600nm, was associated to (4)G5/2→(6)H7/2 of Sm(3). Emission lines at 528, 548, 662 at 852nm were also seen for CaSnO3:Er(3+) and correspond to Er(3+) intra-4f(n) shell transitions. In addition, at low temperatures, a stark splitting of the 4f electron energy levels of the Er(3+) ions were observed in infrared region (1520-1558nm) and assigned to the transition between the (4)I13/2 state and the (4)I15/2 state. Finally, our results show that the rare earth doped CaSnO3 has remarkable potential for applications as optical material since it exhibits efficient and sharp emissions due to rare earth ions.

Catholuminescence properties of rare earth doped CaSnO3 phosphor.

The present study describes cathodoluminescence (CL) properties of CaSnO3 phosphors doped with Eu(3+), Tb(3+) and Dy(3+) synthesized by a solid-state method. X-ray diffraction (XRD) patterns confirm that CaSnO3 sintered at 1200°C exhibits orthorhombic structure. The evidence and rationale for two strong broad emission bands appeared at 360 and 780nm for undoped CaSnO3 are presented. The CL measurements exhibit that the 4f-4f emissions from (5)D4→(7)F6 (490nm), (5)D4 →(7)F5 (544nm), (5)D4 →(7)F4 (586nm) and (5)D4 →(7)F3 (622nm), assigned to possible transitions of Tb(3+) ions are seen. The strongest one, observed at 544nm, due to its probability of both magnetic and electric transitions make the sample emission green. Emissions at 480, 574, 662 and 755nm were detected for the CaSnO3:Dy(3+) and attributed to the transitions from the (4)F9/2 to various energy levels (6)H15/2, (6)H13/2, (6)H11/2 and (6)H9/2+(6)F11/2 of Dy(3+), respectively. CL spectra of Eu doped CaSnO3 reveal that there is a strong emission peak appeared at 615nm due to the electric dipole transition (5)D0→(7)F2 (red). Finally, our results show that the rare earth doped CaSnO3 have remarkable potential for applications as optical materials since it exhibits efficient and sharp emission due to rare earth ions.