Effect of MgO doping on the luminescent properties of ZnO

doi:10.1016/j.mseb.2005.12.028

Materials Science and Engineering: B

Volume 129, Issues 1–3, 15 April 2006, Pages 93-95

https://doi.org/10.1016/j.mseb.2005.12.028 Get rights and content

Abstract

Zn_1−xMg_xO pellets were synthesized using traditional solid-reaction method and luminescent properties were investigated. ZnO doped with MgO reveals long afterglow emission that can last for more than 10 min after the samples were sintered in sealed crucible above a certain temperature. The emission spectra of Zn_1−xMg_xO (0 < x < 1) can be Gaussian fit to two peaks, and the relative intensity of the two emission peaks alters with increasing the sintering temperature. The position of the two emission peaks shows slight red shift when the sintering temperature increases from 1100 to 1250 °C and remains unchanged even though the sintering temperature is further increased. The emission peak in the green region is similar with the single emission band of ZnO, while that in the orange region is related to the long-lasting phosphorescence.

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Acknowledgements

This work was financially supported by National Natural Science Foundation of China under grant no. 50302001and the Beijing Nova Program of China under grant no. H020821250190.

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Among various thin-film growth techniques for ZnMgO, pulsed laser deposition has been a popular technique and solubility limit of up to 33 at% has been reported [4–9]. The synthesis of nanopowders has however been undertaken by a variety of techniques such as solid-sate reaction route [10,11], sol-gel [12], thermal decomposition [13,14], co-precipitation [15], solution-based [16], e-beam evaporation [17] with solubility limits up to around 10–15% and 30 at% by hydrothermal [18] method. The hexagonal wurtzite structure of ZnO was reported to be maintained till x < 0.4.
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Thermoluminescence studies of γ-irradiated ZnO:Mg<sup>2+</sup> nanoparticles
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Pure and Mg²⁺ doped ZnO nanoparticles are synthesized by solution combustion method. X-ray diffraction studies of the samples confirm hexagonal phase. Crystallite size is calculated using Scherer formula and found to be ∼30 nm for undoped ZnO and 34–38 nm for Mg²⁺ doped ZnO. A broad PL emission in the range 400–600 nm with peaks at 400, 450, 468, 483, 492, 517, 553 nm are observed in both pure and Mg²⁺ doped nanoparticles. Near band edge emission of ZnO is observed at 400 nm. The broad band emissions are due to surface defects. PL emission intensity is found to increase with Mg²⁺ concentration up to 1.5 mol% and then decreases due to concentration quenching. Samples are irradiated with γ-rays in a dose range 0.05–8 kGy. Gamma irradiation doesn’t affect PL properties. Undoped samples exhibit unstructured low intense TL glow with peak at 720 K. Whereas Mg²⁺ doped samples exhibit well structured TL glow curves with peak at ∼618 K. TL glow peak intensity of Mg²⁺ doped samples increases with Mg²⁺ concentration up to 2 mol%, thereafter decreases. TL curves of Mg²⁺ (2 mol%) doped ZnO exhibit two glows, a high intense peak at 618 K and a weak one with peak at ∼485 K. TL intensity of Mg²⁺ (2 mol%) doped ZnO samples increases with gamma dose up to 1 kGy and then decreases. Kinetic parameters of TL glows are calculated by deconvolution technique. Activation energy and frequency factor are found to be 1.5 eV and 3.38 × 10¹¹ s⁻¹ respectively.
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The effect of increasing Mg content in the ZnO films was found to reduce the defect emission and to improve strongly the bright excitonic photoluminescence at room temperature. Many recent papers [16–23] have demonstrated that the optical and luminescent properties of ZnMgO films are very sensitive to the defect density, chemical stoichiometry, and crystalline microstructure that depend strongly on the growth temperature and the Mg doping concentration. M. Gohsh et al. [19] have studied the effect of magnesium on the structural and optical properties of Zn1−xMgxO nanocrystals synthesized by low temperature route.
This paper reports morphological and optical characterizations of sintered (ZnO)_1−x(MgO)_x composite materials. The effects of MgO doping content on these pellets properties have been analyzed. The SEM observations have shown rougher surfaces of the samples covered by grains having prismatic shapes and different sizes. From reflectance and absorption measurements, we have determined the band gap energy which tends to augment from 3.287 to 3.827 eV as the doping content increases. This widening of the optical band gap is explained by the Burstein-Moss effect which causes a significant increase of electron concentration (2.89 10¹⁸−5.1910²⁰ cm⁻³). In addition, the absorption coefficient, Urbach energy, optical constants (refractive index, extinction coefficient, dielectric constant) and dispersion parameters, such as E₀ (single-oscillator energy), E_d (dispersive energy) were determined of the (ZnO)_1−x(MgO)_x composites and analyzed.
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2015, Handbook on the Physics and Chemistry of Rare Earths
Persistent luminescence is the phenomenon whereby a material keeps emitting light for seconds to hours after the excitation has stopped. This chapter describes the history of this class of materials and how the discovery of a new family of very efficient persistent phosphors has given a boost to the development of both new materials and applications. Synthesis conditions and analytical techniques specific to persistent luminescent compounds are described, together with ways to evaluate their performance in terms of human eye perception. A state-of-the-art is presented for the materials—hosts and dopants—currently investigated for persistent luminescence, consistently referring to the original literature. Finally, in vivo medical imaging is shown to be a promising but challenging application of long-wavelength persistent luminescence and the relation between persistent luminescence and mechanoluminescence is described.
Effect of Mg doping on photoluminescence of ZnO/MCM-41 nanocomposite
2012, Ceramics International
Citation Excerpt :
Therefore, replacement of Zn by Mg does not give rise to significant changes in lattice constants. Recent studies demonstrate the enhancement in the band edge luminescence in ZnO doped with MgO [15–17] and a very high intense near band edge luminescence was also reported in ZnO-core/SnO2-shell nanorods [18]. It is obvious from these results that MgO doping has great influence on visible emission as well as on UV emission of ZnO.
In this paper, photoluminescence (PL) behavior of Mg_xZn_1−xO/MCM-41 nanocomposite (where x = 0.05, 0.15, 0.25 and 0.30) is reported. Samples were characterized with small angle X-ray diffraction (SAXRD), wide angle XRD, BET (Brunauer–Emmet–Teller) surface area and pore size analyzer, field emission scanning electron microscope (FE-SEM), high resolution transmission electron microscope (HR-TEM) and PL spectrometer. The structure of MCM-41 was confirmed from both SAXRD and BET results. A broad PL band positioned at around 393 nm has been exhibited by ZnO/MCM-41 nanocomposite. With Mg doping, intensity of this PL band decreased for x = 0.05 and 0.15 and above this there was gradual enhancement in intensity. It was found that the intensity of the PL band, strongly depends on the particle size of ZnO. The increase in particle size along with MgO phase separation for x = 0.30 was proved by HR-TEM analysis. Interestingly, the differences in particle sizes at different concentrations of Mg did not account for shift in the PL band. A twofold enhancement in the intensity of PL band when x = 0.30 compared to bare ZnO/MCM-41 nanocomposite was observed. It is attributed for the increase in particle size which preserves the energy saved by passivation of ZnO nanoparticles and the other one is formation of heterojunction structures between ZnO and MgO. It was also evident from these results that there is increase in oxygen vacancies of ZnO crystallites with increase in particle size.

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Effect of MgO doping on the luminescent properties of ZnO

Abstract

Section snippets

Acknowledgements

Thin Solid Films

Solid State Commun.

Nucl. Instr. Meth. Phys. Res. B

J. Lumin.

J. Lumin.

Proc. SPIE

Ind. J. Pure Appl. Phys.