Tb-doped MgAl2O4 phosphors: A study of structural and luminescence characteristics

In the MgO-Al2O3 system, magnesium aluminate spinel (MgAl2O4) is a technologically significant compound due to its unique properties, including a high melting point, low thermal conductivity, excellent thermal shock resistance, chemical inertness, and robust mechanical strength. This compound has diverse applications in refractory materials, catalyst supports, moisture sensors, nuclear techniques, insulating materials, and even military applications. While rare-earth elements are commonly used as dopants in luminescent materials, limited research exists on doping of Tb3+ ions in magnesium aluminate. This study investigates the luminescence properties of Tb3+ doped synthesis magnesium aluminate materials, shedding light on this underexplored area. The combustion method is employed for synthesis, known for producing nano-sized powders with exceptional luminescent properties. Additionally, this study explores Sm3+ ion doping in magnesium aluminate materials and their luminescence properties. Using the combustion synthesis method, structural attributes of Tb3+-doped MgAl2O4 nanophosphors are meticulously examined. Through X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) analyses, coupled with excitation and emission spectra, a comprehensive investigation of the luminescent provide behavior at room temperature is provided. The XRD data reveal Tb3+ doped MgAl2O4 phosphors exhibit a single phase with face centred cubic structure belonging to the Fd3m‾ space group, consistent with the standard JCPDS files (No. 21-1152). Excitation and emission spectra offer valuable insights into the energy transitions within the Tb3+-doped MgAl2O4 phosphors. Furthermore, the study explores the effects of varying Tb3+ ion concentrations on the luminescent properties, revealing an optimal doping concentration of 5 wt% Tb for maximizing emission intensity. Concentration quenching, primarily attributed to dipole-dipole (d-q) interactions, is observed at higher Sm3+ concentrations. In conclusion, this research enhances our understanding of rare-earth ion doping in luminescent materials and highlights the potential applications of Tb3+-doped MgAl2O4 nanophosphors, which offer promise for various technological applications, including lighting and displays.

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 MoO₄^2- 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 ⁴F_9/2 → ⁶H_15/2, ⁴F_9/2 → ⁶H_13/2 and ⁴F_9/2 → ⁶H_11/2, 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.

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.