0000000000082224
AUTHOR
G. Doke
showing 14 related works from this author
EPR studies of the oxyfluoride glass ceramics using Mn2+as a paramagnetic probe
2010
In this work, we used Mn2+ as a dopant in the oxyfluoride glasses with various fluoride compounds. Electron paramagnetic resonance (EPR) measurements were carried out before and after a heat treatment of the material. In both cases, a well pronounced hyperfine (hf) structure of the EPR spectra characteristic to the Mn2+ ion have been observed. EPR measurements have also been studied for the separate fluoride counterparts of the oxyfluoride glasses. EPR spectra of the LaF3:Mn2+ and CaF2:Mn2+ powders show that Mn2+ ion has a strong superhyperfine (shf) interaction with surrounding fluorine nuclei, and this shf structure could be observed also in the heat treated glass samples.
Synthesis of cubic and hexagonal NaYF4:Er3+
2012
Up-conversion luminescence process, which is related to absorption of several light photons (usually infrared) followed by emission of light in the visible or even ultraviolet spectral regions, has attracted interest of scientists due to its potential practical use in various applications including biolabels, temperature sensors, light sources etc. Although observable in d- and f-ions doped materials, the highest efficiency of up-conversion luminescence is usually attained in lanthanides doped hosts. Among huge variety of materials suitable as up-conversion hosts the most prominent is considered to be NaYF4, both due to its low phonon energy and multisite nature of the crystalline lattice. …
Novel synthesis of up-conversion phosphor based on rare-earth doped NaLaF4
2011
In this work Er3+ doped NaLaF4 material has been synthesized Along with the description of the synthesis route, luminescence spectra and decay kinetics of both traditional and up-conversion luminescence of Er3+ will be presented for different Er3+ doping levels. It will be shown that the main mechanisms involved in the creation of the up-conversion luminescence in NaLaF4:Er3+ under excitation at about 975 nm are excited state absorption and energy transfer. Relative impact of either of the mechanisms in NaLaF4:Er3+ depends on both the concentration of Er3+ and on the excitation wavelength: the increase of either the concentration or the excitation wavelength leads to the prevalence of energ…
Cathodoluminescence of oxyfluoride glass-ceramics
2013
Abstract Tb, Ce, Eu activated oxyfluoride glass-ceramics with the composition SiO2 · Al2O3 · Li2O · LaF3 have been studied by cathodoluminescence (CL). We compared CL intensities and decay times of the Tb, Ce, Eu activated glass-ceramic samples and observed that the Tb activated sample has the most intense luminescence, but the Ce activated sample has the shortest decay times. Induced optical absorption and thermostimulated luminescence have been observed after X-ray irradiation of samples.
Oxygen influence on luminescence properties of rare-earth doped NaLaF 4
2016
Abstract Luminescence properties of erbium and europium doped NaLaF4 with different oxygen content have been studied. Vacuum ultraviolet (VUV) excitation luminescence spectroscopy technique has been applied by using synchrotron radiation excitation. It was found that oxygen impurity leads to significant degradation of Er3+ or Eu3+ emission under VUV excitation. The intensive O2−–Er3+ charge transfer excitation band has been detected from oxygen abundant NaLaF4 in the 150–165 nm spectral range. This band reveals a competing absorption mechanism in oxygen containing NaLaF4. It is clearly demonstrated that one reason for the Er3+ emission degradation in oxygen abundant NaLaF4 is strong suppres…
Angular dependence of recombination luminescence-detected EPR in a ZnO crystal
2015
Angular dependency of electron paramagnetic resonance, optically detected by UV-excited recombination luminescence (RL-EPR), was measured for nominally pure ZnO single crystals. Observed magnetic resonances belong to the broad yellow RL band with slow decay centred at 610 nm, which is characteristic of untreated ZnO crystals. In the sample, irradiated with the 266 nm UV laser, an additional RL band centred at 740 nm appears, which has considerably faster decay time than the yellow one. This RL band is characteristic of the luminescence of Fe3+ ions in the ZnO crystals. It could be observed only after the UV laser treatment. No RL-EPR signal was detected for this RL band. Our spectral simula…
Rare Earth Activated Oxyfluoride Glasses and Glass-Ceramics for Scintillation Applications
2012
Oxyfluoride glasses 49SiO2·6Al2O3·24Li2O·20LaF3 activated with Tb, Ce, Eu have been synthesized and studied. After heating at 580°C and 750°C crystalline phases were obtained. The samples were studied by DTA (Differential thermal analyzer), CL (cathodoluminescence), XRD (X-ray diffraction), SEM (scanning electron microscope), EDS (energy dispersive x-ray spectroscopy) methods. We found out that presence of crystalline phase enhances the CL of Tb activated samples significantly; whereas, the shortest decay time of 0.29 μs has been observed for less intense Ce doped glass sample.
Selective excitation of up-conversion luminescence by Yb3+–Er3+ energy transfer in glass and crystalline phase of oxyfluoride glass ceramics
2010
Up-conversion luminescence of oxyfluoride glass and glass ceramics containing LaF3 crystallites doped with Yb 3+ and Er 3+ was investigated at low temperature. Excitation of Yb 3+ in the IR region revealed the fast and the slow components of Er 3+ up-conversion luminescence originating from both glass and crystalline phases. The temporal differences of the both kinds of the luminescence allowed reconstructing the excitation spectra of the up-conversion luminescence related to the glass and crystalline phases in the glass ceramics. 2010 Elsevier B.V. All rights reserved.
Comprehensive study on different crystal field environments in highly efficient NaLaF4:Er3+ upconversion phosphor
2015
Abstract Complex fluorides, especially rare-earth doped NaREF 4 (RE = Y 3+ , La 3+ or Gd 3+ ), are promising materials for the upconversion luminescence mostly due to low phonon energy of their matrices and multisite nature of the crystalline lattice. Although multisite formation in hexagonal NaREF 4 structures has generally been proved, the actual number of the active sites in different structures varies from two (NaGdF 4 ) to seven (NaYF 4 ). The aim of this work has been to study multisite formation in NaLaF 4 :Er 3+ . For this purpose low-temperature site-selective spectroscopy measurements in hexagonal NaLaF 4 :Er 3+ have been performed. Excitation at different wavelengths correspondin…
Photoluminescence of neodymium and erbium doped NaLaF4 material
2013
Abstract In the course of this research several NaLaF 4 samples doped with different Er 3+ and Nd 3+ concentrations have been synthesized. For these samples photoluminescence spectra, kinetics and excitation spectra have been measured. It has been found that when samples containing Nd 3+ and Er 3+ impurities are excited in specific Nd 3+ bands not only Nd 3+ but also Er 3+ luminescence bands appear. The studies of the decay kinetics show that there is an energy transfer from Nd 3+ to Er 3+ , moreover “green” and “red” Er 3+ luminescence bands appear as result of two different energy transfer mechanisms. In addition, photoluminescence processes in Nd 3+ ions are investigated. Based on the ob…
UV and X-ray excited red persistent luminescence in Mn2+ doped MgGeO3 material synthesized in air and reducing atmosphere
2021
Abstract Materials with long persistent luminescence (PersL) have caused widespread interest among scientists and industry for decades. Currently, there is widely available information on the long persistent luminescence materials with emission in the blue and green spectral range, while the number of publications on the afterglow in the red and near-infrared spectral range is considerably lower. In the course of this work MgGeO3 material doped with 0.1 mol% Mn2+ was produced using solid-state reaction synthesis in ambient and reducing atmospheres. The material exhibits a broad luminescence band with a peak around 680 nm, excited by either X-rays or UV. After cessation of irradiation, the a…
Multicolor Up-Conversion Luminescence in Rare-Earth Doped NaLaF4
2011
In this work we tried to achieve multicolor up-conversion luminescence in low phonon energy material NaLaF4 doped with different Er3+ Tm3+ and Yb3+ concentrations. Up-conversion luminescence was measured and main luminescence bands from Er3+ and Tm3+ in red, green and blue spectral regions were observed. The relative intensities of the luminescence bands could be changed by changing the doping levels of rare-earth ions. Changes in the up-conversion luminescence color could be achieved by applying different infrared pump power density. The color coordinates of the multicolor up-conversion luminescence depending on doping level as well as on the pump power density were presented in CIE (x, y)…
Recent Developments in Cladding-Pumped Doped Fiber Amplifiers for Telecommunications Systems
2020
This paper aims to review recent developments in the field of doped fiber-based optical amplifiers and serve as a reference for promising optical signal amplification techniques that may be useful for practical implementation in high-capacity and cost-efficient telecommunications systems. The main focus is put on different rare-earth dopant elements, double-clad fibers, and optical couplers for cladding-pumping technique. It is found that codoped double-clad fiber-based amplifiers currently have attained the main research interest and show possible application also in multichannel fiber optical transmission systems. Additionally, we have compared different free space and waveguide construct…
Excited state absorption and energy-transfer mechanisms of up-conversion luminescence in Er3+-doped oxyfluoride glass ceramics at different temperatu…
2010
Abstract Oxyfluoride silicate glass SiO2–Al2O3–Na2CO3–NaF–LaF3–ErF3 was synthesized. The glass transition and crystallization temperatures were determined by differential thermal analysis. Glass ceramics containing LaF3:Er3+ crystallites of size ∼20 nm were formed in the glass matrix after the heat treatment of the precursor glass in the vicinity of the crystallization temperature. Up-conversion luminescence, excitation spectra as well as time-resolved up-conversion luminescence of the glass and glass ceramics were studied at different temperatures. The up-conversion transients showed that at room temperature the dominant mechanism of the up-conversion luminescence in the glass ceramics is …