In the course of this research several NaLaF4 samples doped with different Er3+ and Nd3+ concentrations have been synthesized. For these samples photoluminescence spectra, kinetics and excitation ...spectra have been measured. It has been found that when samples containing Nd3+ and Er3+ impurities are excited in specific Nd3+ bands not only Nd3+ but also Er3+ luminescence bands appear. The studies of the decay kinetics show that there is an energy transfer from Nd3+ to Er3+, moreover “green” and “red” Er3+ luminescence bands appear as result of two different energy transfer mechanisms. In addition, photoluminescence processes in Nd3+ ions are investigated. Based on the obtained experimental results luminescence and energy transfer processes in NaLaF4:Er3+, Nd3+ material are discussed.
•Energy transfer from Nd3+ to Er3+ in NaLaF4:Er3+, Nd3+ samples has been observed.•Er3+ luminescence bands appear as result of different energy transfer mechanisms.•Possible luminescence and energy transfer mechanisms have been offered.
In this work, NaLaF
doped with Er
of different concentrations was synthesized. The luminescence spectrum for NaLaF
:Er
(0.2 mol%) at 489 nm excitation reveals characteristic Er
luminescence bands in ...the green (540 nm), red (660 nm) and infrared (980 nm) spectral regions. The green luminescence band originated from the
→
transition is the most intensive one in the luminescence spectrum. As the concentration of the activator is increasing, the intensity of all luminescence bands changes significantly. The super-linear increase of the infrared luminescence intensity with increasing Er
concentration as well as the quenching of green luminescence at the concentrations exceeding 2 mol% can be attributed to the cross-relaxation process between the activator ions.
Darbā pētīta Er
fotoluminiscences atkarība no Er
koncentrācijas NaLaF
matricā. Pieaugot Er
koncentrācijai līdz 2mol% luminiscences intensitātes raksturīgajām Er
joslām zaļā (540nm), sarkanā (660nm) un infrasarkanajā (980 nm) spektra apgabalā pieaug. Pie Er
koncentrācijas virs 2mol% novērojama izteikta zaļās luminiscences koncentrācijas dzēšana un virslineārs infrasarkanās luminiscences joslas pieaugums, kas saistīts ar kross-relaksācijas procesiem starp aktivatora joniem.
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) chromaticity diagram (1931).
The F-type centres in YAG crystals Pujats, A.; Springis, M.
Radiation effects and defects in solids,
11/1/2001, Letnik:
155, Številka:
1-4
Journal Article, Conference Proceeding
Recenzirano
The comparative study of optical properties of thermochemically reduced undoped YAG (Y
3
Al
5
O
12
) crystals is reported. A particular type of the centres often observed in YAG crystals synthesized ...as well as treated under the reducing atmosphere is related to an anion vacancy with one or more trapped electrons (F-type centres in YAG crystals). The changes of photoluminescence intensity and absorption bands intensity of the observed centres under X-irradiation support the F- and F
+
-centre models. It is shown that the F-centre absorption involves at least two bands, at 195 nm and 240 nm, where the broad F-centre luminescence band at 460 nm can be excited. It is suggested the existence of the F
−
-centre could be connected with the absorption bands at 360 nm, 480 nm, and 830 nm.
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 energy transfer mechanism over excited state absorption mechanism.
Luminescent detectors of ionising radiation Kulis, P.; Rogulis, U.; Springis, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2003, Letnik:
509, Številka:
1-3
Journal Article
Recenzirano
At present in slow neutron imaging an active layer of an imaging plate IP contains a mixture of storage phosphors, usually BaFBr:Eu2+ used for imaging of X-rays, and a neutron converter material, ...usually Gd2O3, LiF.
A novel Li-containing luminescent material perspective for a direct neutron conversion and storage is discussed. Irradiation of LiBaF3 crystals results in generation of Frenkel defect pairs and creation of F-type centres responsible for three absorption bands in UV-and visible spectral region. Because photo-stimulation in each of these absorption bands leads to bleaching of induced absorption, the F-type colour centres are convenient for storage of radiation dose. Photo-stimulated decay of F-centres causes recombination luminescence of impurity centres. Thermoactivated decay of F-type centres is governed by ionic process. The thermal stability of F-centres at RT and consequent material storage characteristics can be improved by doping of the LiBaF3 with heterovalent oxygen impurities. The obtained radiation energy storage, photo- and thermostimulated read-out characteristics justify that LIBaF3 is a suitable active media for imaging of slow neutrons.
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