Investigative study of Mn2+ concentration on the structure, morphology and photoluminescence of sol-gel ZnAl2O4/ZnO/ SrAl2O4/Sr3Al2O6 mixed phase nanophosphor (original) (raw)
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Physica B: Condensed Matter, 2009
ZnS and SiO 2 -ZnS nanophosphors, with or without different concentration of Mn 2 + activator ions, were synthesized by using a sol-gel method. Dried gels were annealed at 600 1C for 2 h. Structure, morphology and particle sizes of the samples were determined by using X-ray diffraction (XRD), highresolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM). The diffraction peaks associated with the zincblende and the wurtzite structures of ZnS were detected from as prepared ZnS powders and additional diffraction peaks associated with ZnO were detected from the annealed powders. The particle sizes of the ZnS powders were shown to increase from 3 to 50 nm when the powders were annealed at 600 1C. An UV-Vis spectrophotometer and a 325 nm He-Cd laser were used to investigate luminescent properties of the samples in air at room temperature. The bandgap of ZnS nanoparticles estimated from the UV-Vis data was 4.1 eV. Enhanced orange photoluminescence (PL) associated with 4 T 1 -6 A 1 transitions of Mn 2 + was observed from as prepared ZnS:Mn 2 + and SiO 2 -ZnS:Mn 2 + powders at 600 nm when the concentration of Mn 2 + was varied from 2-20 mol%. This emission was suppressed when the powders were annealed at 600 1C resulting in two emission peaks at 450 and 560 nm, which can be ascribed to defects emission in SiO 2 and ZnO respectively. The mechanism of light emission from Mn 2 + , the effect of varying the concentration on the PL intensity, and the effect of annealing are discussed.
Journal of Electronic Materials
Zinc aluminate (ZnAl 2 O 4) host and 0.01% Cr 3+ doped were successfully prepared using the sol-gel method. The annealing time (AT) was varied in the range of 0.5-19 h. The X-ray diffraction results showed that the AT does not affect the crystal structure of the prepared powders. Scanning electron microscopy (SEM) results showed that the morphology of the prepared nanophosphors was influenced by the AT. Energy dispersive x-ray spectroscopy (EDS) confirmed the homogeneous distribution of the constituent elements. Transmission Electron microscopy (TEM) suggested that the average crystallites sizes of the ZnAl 2 O 4 to be ~ 20 nm. Ultraviolet-visible (UV-Vis) spectroscopy results revealed that the bandgap (E g) of the prepared nanophosphor can be tuned by varying the AT. The emission peak at 390 nm is attributed to the intrinsic defects within the host material bandgap. The emission peak at 572 nm is attributed to both contribution from the host and Cr 3+ (4 T 1 → 4 A 2) transition. The maximum PL intensity was observed from the samples annealed for 3 h. The International Commission on Illumination (CIE) chromaticity diagram showed a slight shift on the blue emission with an increase in AT.
Abstract: Nanophosphor β-Zn2SiO4:Mn with bright yellow light emission were synthesized by a sol–gel process. These samples were prepared by a simple solid-phase reaction under natural atmosphere at 1500 °C after the incorporation of ZnO:Mn nanoparticles, in silica monolith. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the phase purity, particle size and morphology. In addition photoluminescence (PL) was used for optical study. The PL spectrum for the β-Zn2SiO4:Mn nanophosphors showed a dominant peak at 574 nm, which originated from the 4T1 → 6A1 transitions of Mn2+ ions. The level of manganese doping did not greatly affect the crystallinity, but did affect the luminescence of nanophosphors. Upon 255 nm excitation, the luminescence decay time of the yellow emission of β-Zn2SiO4 with a Mn doping concentration of 2 at.% around 574 nm is 13 ms. The characteristics of crystallinity, morphology and luminescence property of the obtained nanophosphors were investigated.
Results in Physics, 2019
Neodymium activated strontium zinc aluminate (Sr 3 ZnAl 2 O 7 :x%Nd 3+) nanophosphor was synthesized using the sol-gel technique whereby the Nd 3+ concentration was varied in the range 0 ≤ x ≤ 2. The effect of Nd 3+ concentration on the structure, particle morphology and photoluminescence properties of Sr 3 ZnAl 2 O 7 were investigated. The X-ray diffraction (XRD) results revealed that all samples resembled the mixture of both ZnAl 2 O 4 and Sr 3 Al 2 O 6 cubic structures. Nd 3+ doping influenced the crystallite sizes of the prepared phosphor materials. The energy dispersive X-ray spectroscopy (EDS) results confirmed the presence of all expected elements in the composition. Scanning electron microscopy (SEM) revealed that as the Nd 3+ concentration increased the surface morphology changed to smooth mountain-like structures. The ultraviolet-visible (UV-Vis) diffuse reflection spectroscopy showed that the band gap of Sr 3 ZnAl 2 O 7 can be tuned from 2.74 to 2.95 eV by increasing the Nd 3+ concentration. When the host is excited above the bandgap (374 nm), broad emission attributed to defects occurs with the maximum near 585 nm. Doped samples excited in this manner do not exhibit additional luminescence due to the Nd 3+ ions, but in contrast there is a small dip in the defect emission band near 585 nm due to absorption attributed to Nd 3+ ions. Characteristic infrared emissions of Nd 3+ ions at 885, 1064 and 1340 nm were observed by directly exciting the Nd 3+ ions at 585 nm (4 I 9/2 → 5 G 5/2 + 2 G 7/2) and were attributed to 4 F 3/2 → 4 I 9/2, 4 I 11/2 and 4 I 13/2 transitions, respectively. The Commission Internationale de l'Eclairage (CIE) coordinates results showed that the orange emission colour is from the host.
Structure and luminescence of (Zn,Mg)O:Zn2+ nanophosphor films
Materials Letters, 2008
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Physica B Condensed Matter
a b s t r a c t ZnS and SiO 2 –ZnS nanophosphors, with or without different concentration of Mn 2 + activator ions, were synthesized by using a sol–gel method. Dried gels were annealed at 600 1C for 2 h. Structure, morphology and particle sizes of the samples were determined by using X-ray diffraction (XRD), highresolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM). The diffraction peaks associated with the zincblende and the wurtzite structures of ZnS were detected from as prepared ZnS powders and additional diffraction peaks associated with ZnO were detected from the annealed powders. The particle sizes of the ZnS powders were shown to increase from 3 to 50 nm when the powders were annealed at 600 1C. An UV–Vis spectrophotometer and a 325 nm He–Cd laser were used to investigate luminescent properties of the samples in air at room temperature. The bandgap of ZnS nanoparticles estimated from the UV–Vis data was 4.1 eV. Enhanced o...
An effective nanostructured green phosphor Zn2SiO4:Mn2+ prepared by sol-gel method
Nanosystems: Physics, Chemistry, Mathematics, 2018
A nanostructured willemite doped with manganese (Zn 2 SiO 4 :Mn 2+) was synthesized by sol-gel method followed by high-temperature annealing. Prepared Zn 2 SiO 4 :Mn 2+ is characterized by average particle size of 100 nm, narrow particle size distribution, and high crystallinity. Under UV-excitation nanostructured willemite shows an intensive photoluminescence at 520 nm corresponded to activator Mn 2+ emission. It was found that the emission decay curves of willemite becomes non-exponential with increasing of manganese content. Zn 2 SiO 4 :Mn 2+ reveals long-lasting phosphorescence up to 45 ms. Absolute quantum yield of Zn 2 SiO 4 :Mn 2+ reaches 47 % at 0.1 at. % of Mn 2+. The luminescence concentration quenching effect at Mn 2+ concentration higher than 1 at % is observed.
Bulletin of Materials Science, 2002
Synthesis and characterization of undoped and Mn 2+ doped ZnS nanocrystallites (radius 2-3 nm) embedded in a partially densified silica gel matrix are presented. Optical transmittance, photoluminescence (PL), ellipsometric and electron spin resonance measurements revealed manifestation of quantum size effect. PL spectra recorded at room temperature revealed broad blue emission signal centred at ~ 420 nm and Mn 2+ related yellow-orange band centred at ~ 590 nm while ESR indicated that Mn in ZnS was present as dispersed impurity rather than Mn cluster.
Journal of Molecular Structure, 2019
Nanophosphor powders of the mixed phases of ZnAl 2 O 4 /ZnO/SrAl 2 O 4 /Sr 3 Al 2 O 6 (ZZSS) doped with Tb 3þ (ZZSS:0.025%Tb 3þ) were successfully prepared by sol-gel technique. The effect of the annealing period at a fixed annealing temperature (1000 C) and dopant concentration (0.025% Tb 3þ) on the structure and photoluminescence properties was investigated. X-ray diffraction results revealed that the crystallite size was influenced by the annealing period. Scanning electron microscopy showed that varying the annealing period influenced the particle morphology of the prepared nanophosphor material. High resolution transmission electron microscopy confirmed that the prepared material is on the nanoscale. The photoluminescence results showed that the ZZSS emits at 585 nm when excited at 374 nm, which is attributed to the defects centres within the ZnO phase. The Tb 3þ doped samples showed emissions peaks at 545, 590 and 623 nm which were attributed to the 4f transitions of Tb 3þ , specifically 5 D 4 / 7 F J (J ¼ 5, 4, 3). Increasing the annealing period up to 5.4 h led to luminescence enhancements, while a further increase led to quenching. The Commision Internationale de l'Eclairage coordinates showed that the greenish emission colour could be tuned by varying the annealing period.
Scripta Materialia, 2008
A novel procedure for Zn 2 SiO 4 :Mn 2+ phosphor powder synthesis based on a combination of sol-gel and combustion methods is presented. The procedure utilizes Zn-nitrate, Mn-nitrate, tetraethylorthosilicate and polyethylene glycol to produce gel, which is then combusted in a microwave oven to form Zn 2 SiO 4 :Mn 2+ powder and further annealed to crystallize in desired structure. The material has been investigated by X-ray diffraction, scanning electron microscopy, infrared and photoluminescence spectroscopy. These investigations showed well-crystallized powder particles exhibiting intense green light emission.