In this study, Strontium Bismuth Niobate (SrBi2-xTmxNb2O9 with 0 ≤ x ≤ 0.1) doped by Tm was synthesized using by the hydrothermal method. The microstructure and electrical properties were mainly ...investigated. XRD analysis showed a single-phase orthorhombic structure for Tm-doped SrBi2Nb2O9 samples. The crystallite size is anisotropic and the strain is apparently independent of Tm amount. Dielectric properties for doped SrBi2Nb2O9 with Tm3+ ion have the same trend discussed for the pure sample. FTIR resulats showed that NbO6 octahedral is formed, on one hand, and on the other hand, it shows that spectras for doped and undoped samples are nearly the same. The Cross-section of ceramics showed the plate-like morphology, also the distribution of the pore in ceramics are observed for all samples. Tm dopants produce only minor changes in the impendence parameter values at room temperature. The luminescent (PL) properties of Tm-doped SrBi2Nb2O9 ceramic powders were investigated. The optimum Tm3+ concentration for the maximum PL intensity was found to be at x = 0.075.
In this paper we will be presenting JOES (Judd-Ofelt from Emission Spectra), an application software for calculation of the Judd-Ofelt intensity parameters and derived quantities from the emission ...spectra of Eu3+ doped materials. The program is written to be user friendly and it requires no previous experience in the field of study. This Free and Open-Source program written in JAVA, works on Windows, Linux and MAC OS operating systems. Program has been tested on three europium doped oxides with good luminescent properties: TiO2:Eu3+, ZrO2:Eu3+ and Nb2O5:Eu3+. We wish to give to the researchers this theoretical tool which can make the calculations easier, faster and more reliable.
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•Plasma electrolytic oxidation (PEO) of tungsten in 2 g/L Na3PO4⋅12H2O + 2 g/L NaAlO2.•The majority of micro-discharges during the PEO are tiny and low in intensity.•The high melting temperature of ...tungsten prevents the formation of tungsten plasma.•Tungsten is present in extremely small amounts in the coatings (<1%).•Oxide coating are mainly composed of triclinic WO3 and amorphous Al2O3.
We demonstrated that using a water solution containing 2 g/L Na3PO4⋅12H2O + 2 g/L NaAlO2 as an electrolyte allows for plasma electrolytic oxidation (PEO) on tungsten. During PEO, micro-discharges are tiny, and the optical emission spectrum solely shows lines of electrolyte species (H, Na, and O). Tungsten is present in extremely small amounts in the coatings (<1%), with the majority of the components coming from the electrolyte. The primary ingredients in all of the coatings are amorphous Al2O3 and triclinic WO3.
An extension of the Judd-Ofelt theory, a theoretical model to the field of Luminescence intensity ratio method in phosphor thermometry has been presented, that enables a calculation of thermometric ...figures of merit: sensitivity, maximum sensitivity and temperature resolution, by the Judd-Ofelt intensity parameters. The model is applicable for 7 out of 14 lanthanides, and as a testing ground for the model's adequacy, Y2O3 doped with three different Eu3+ concentrations had been chosen. PL spectra were recorded up to 480 °C and photoluminescence and thermometric properties have been obtained. Conventionally estimated thermometric figures of merit have been compared to those obtained by a Judd-Ofelt thermometric model, with a good matching. Consequently, a novel method for calculation of magnetic dipole strength of the mixed induced electric dipole and magnetic dipole transition has been developed. Additionally, an interactive application software has been developed for the quick evaluation of the sensitivity and temperature resolution from Judd-Ofelt intensity parameters.
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•Judd-Ofelt model for predicting thermometric sensor properties is presented.•Sensitivities and temperature resolutions can be estimated from Judd-Ofelt parameters.•Model is tested on Y2O3:Eu3+ up to 480 °C with good matching to experiment.•Explicit model equations for 7 lanthanides are presented.•Software for predicting sensor properties is created for fast calculation.
In this study, plasma electrolytic oxidation (PEO) of zinc in a water solution containing 10 g/L Na3PO4⋅12H2O + 2 g/L KOH, was used for the preparation oxide of coatings for application in ...photocatalysis for degradation of organic dyes. Degradation of methyl orange (MO) as a model of organic dyes under simulated sunlight was used. In coating formed after 2 min of PEO, the pure phase hexagonal wurtzite ZnO was identified, while in coatings formed for a long time of PEO (up to 5 min) monoclinic phase of Zn3(PO4)2 was identified together with ZnO (ZnO/Zn3(PO4)2 coatings). ZnO/Zn3(PO4)2coatings show better photocatalytic activity (PA) than ZnO coating. The ZnO/Zn3(PO4)2 coating with the highest PA was formed after 4 min. Coupling ZnO with Zn3(PO4)2 reduce the recombination rate of photo-generated electron/hole pairs in ZnO which leads to an increase in PA of ZnO/Zn3(PO4) coatings compared to pure ZnO coating. This is confirmed by photoluminescent measurements. According to photocatalytic and photoluminescence measurement mechanism of the light-induced degradation of MO over ZnO/Zn3(PO4)2 coatings is suggested.
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•PEO of Zn in phosphate electrolyte was used to create ZnO and ZnO/Zn3(PO4)2 coatings.•Photocatalytic activity (PA) of ZnO/Zn3(PO4)2 is better than ZnO.•The ZnO/Zn3(PO4)2 coating with the highest PA was formed for 4 min.•Coupling ZnO with Zn3(PO4)2 reduce the recombination rate of photo-generated electron/hole pairs in ZnO.
Eu3+ doped Zirconia coatings were synthesized by the electrochemical plasma electrolytic oxidation method in only 8 min from the pure zirconium substrate. The phase constitution from pure monoclinic ...to pure tetragonal and exactly in between was achieved by using different concentrations of Na3PO4 and NaAlO2 electrolytes. The complex emission spectra composed of Eu2+, Eu3+, and ZrO2 defect emission greatly depend on the excitation wavelength and phase constitution. Eu3+ photoluminescence properties depend on the phase, which is reflected by the different Stark splitting and different intensities of transitions. Thus, both phase and photoluminescent properties of ZrO2 coatings are fine-tuneable. Judd-Ofelt analysis was performed from the emission and excitation spectra, showing that all 3 intensity parameters depend linearly on the phase constitution, being largest in the pure monoclinic phase. The mixed phase has Judd-Ofelt parameters between those in pure phases. Eu3+ has 2.45 times more preference to get incorporated into the tetragonal than in the monoclinic phase in the mixed phase samples. The general equation for Judd-Ofelt parameters in a compound with mixed constituents and probability of incorporation is introduced, allowing also for a prediction of the spectrum shape based on the Judd-Ofelt parameters of pure-phase compounds. Python software code for estimating the percent of incorporation by multiple linear regression model is also provided.
•Under 8 min of plasma electrolytic oxidation, ZrO2:Eu3+ samples were prepared.•Monoclinic, tetragonal, or 50/50 mixed phase was controlled by exact electrolyte concentrations.•Spectral characteristics and Judd-Ofelt analysis greatly depend on the phase.•A novel theoretical method for estimating the phase preference of incorporating dopant ions is given.•The method can be used for any host composition, and free software is provided for easy calculations.
15 μm thick ZrO2:Nd3+ coatings were synthesized by the plasma electrolytic oxidation process from the pure zirconium substrate in an alkaline electrolyte with the addition of five different ...concentrations of Nd2O3 powders. SEM/EDS images show morphologies characterized by numerous pores and cracks, and uniform distribution of coating constituents. XRD revealed that the monoclinic phase is dominant and that Nd impurity stabilizes the tetragonal phase. The average crystalline size is 27.5 nm. XRF revealed a linear increase in incorporated Nd with increasing Nd2O3 concentration. Photoluminescence spectra are characterized by the NIR emissions at typical energies for Nd3+ ion. The highest emission intensity is obtained with 2.0 g/L Nd2O3. The explicit equation for branching ratios in relation to the emission intensities and Judd-Ofelt parameters is recalculated. A novel, more precise equation for the calculation of the spectroscopic quality factor from the most intense emissions is presented. The spectroscopic quality factor is the lowest in the sample with the highest photoluminescent intensity, and is one of the lowest values, in comparison with the 203 spectroscopic quality factors calculated from the Judd-Ofelt parameters in the literature. The luminescence intensity decreases with temperature by the phonon-assisted cross-relaxation mechanism. The luminescence thermometry by the lifetime of 4F3/2 level shows ∼2% K−1 relative sensitivity in the 300–380 K temperature range.
•ZrO2:Nd3+ coatings created by Plasma electrolytic oxidation.•Tetragonal/monoclinic phase ratio proportional to Nd3+ content.•New equation given for calculation of the spectroscopic quality factor.•Very low values of spectroscopic quality factor compared with 203 Nd-doped compounds.•Lowest spectroscopic quality factor and highest emission intensity with 2 g/L of Nd2O3.
In this paper, Dy3+ and Dy3+/Ce3+ doped Al2O3 coatings were synthesized by plasma electrolytic oxidation process of aluminum. Structural and photoluminescence (PL) properties of obtained coatings as ...well as energy transfer mechanism from Ce3+ to Dy3+ were studied. The PL excitation and emission spectra of Al2O3:Dy3+ featured weak bands attributed to f-f transitions of Dy3+. The PL emission spectrum of Al2O3:Dy3+ exhibits three emission bands in blue-yellow-red regions, assigned to 4F9/2→6H15/2, 4F9/2→6H13/2, and 4F9/2→6H11/2 transitions of Dy3+, respectively. Under middle UV excitation the Ce3+ in Al2O3 emits broad band, peaked at about 330 nm, attributed to the 5d→4f transition of Ce3+. Because of the strong overlap between the PL emission of Ce3+ and the PL excitation of Dy3+ in Al2O3, energy transfer from Ce3+ to the Dy3+ in Al2O3:Dy3+/Ce3+ is observed upon 285 nm excitation. PL emissions due to 4F9/2→6HJ (J = 11/2, 13/2, and 15/2) transitions of Dy3+ in Al2O3:Dy3+/Ce3+ is two to three orders of magnitude larger than in Al2O3:Dy3+. The values of CIE chromaticity coordinates for Al2O3:Dy3+/Ce3+ suggest their application for cold white light emission.
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•Al2O3:Dy3+ and Al2O3:Dy3+/Ce3+ coatings are formed by PEO of aluminum.•PL emission spectra of Al2O3:Dy3+/Ce3+ exhibit bands inherent to Dy3+ and Ce3+.•Ce3+ is a very efficient sensitizer for Dy3+ PL enhancement.•Energy transfer efficiency from Ce3+ to Dy3+ increases with increasing Ce3+ content.
Nb2O5:Eu3+ and Nb2O5:Sm3+ coatings have been successfully deposited by plasma electrolytic oxidation of niobium in 0.1 M phosphoric acid containing either Eu2O3 or Sm2O3 powder. Surface morphology ...and chemical composition of obtained coatings are correlated to the mechanism of oxide growth during the PEO process. X-ray photoelectron spectroscopy revealed that Nb and P in the oxide coatings are in pentavalent, while Eu and Sm are in trivalent oxidation state. Nb2O5:Eu3+ and Nb2O5:Sm3+ oxide coatings are found to be in low crystallinity pseudohexagonal Nb2O5 form. Photoluminescent emission spectra of either type of coatings are characterized by sharp emission bands in orange-red region ascribed to f–f transitions of Eu3+ ions from excited level 5D0 to lower levels 7FJ (J = 0, 1, 2, 3, and 4) and Sm3+ ions from excited level 4G5/2 to the lower levels 6HJ (J = 5/2, 7/2, 9/2, and 11/2). It is observed that the intensity of peaks in excitation and emission photoluminescent spectra increases with the concentration of Eu3+ and Sm3+, i.e. time of PEO, but the peak positions remain virtually unchanged. The fact that in Nb2O5:Eu3+ and Nb2O5:Sm3+ coatings electrical dipole transition is much more intense than magnetic dipole transition indicates that Eu3+ and Sm3+ ions occupied non-inversion symmetry sites in Nb2O5:Eu3+ and Nb2O5:Sm3+ coatings, respectively.
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•Nb2O5:Eu3+ and Nb2O5:Sm3+ coatings are formed by plasma electrolytic oxidation.•PL spectra exhibit well pronounced bands inherent to Eu3+ and Sm3+ ions.•PL bands related to transitions of Eu3+ from level 5D0 to levels 7FJ are observed.•PL bands related to transitions of Sm3+ from level 4G5/2 to levels 6HJ are observed.•Eu3+ and Sm3+ ions occupied non-inversion symmetry sites in the coatings.
Orthorhombic Ta
2
O
5
:Er
3+
coatings were obtained by plasma electrolytic oxidation (PEO) of tantalum in an alkaline electrolyte with the addition of Er
2
O
3
particles in various concentrations. ...Down-conversion photoluminescence (PL) emission spectra is featured by sharp bands attributed to 4f–4f transitions of Er
3+
. The most intense green PL emission band centered at 544 nm is attributed to the
4
S
3/2
→
4
I
15/2
emission of Er
3+
. Population paths of the Er
3+
down-conversion PL happen under resonant excitation conditions of the Er
3+
from ground state
4
I
15/2
to higher levels, and via a broad violet charge transfer excitation band. Both excitation energy and Er content have an impact on the PL emission response in Ta
2
O
5
:Er
3+
coatings. The
4
I
15/2
→
4
G
11/2
transition is the dominant excitation pathway for the PL emission of Er
3+
. Up-conversion PL spectra created after 980 nm irradiation of Ta
2
O
5
:Er
3+
coatings have characteristic 4f–4f transitions of Er
3+
. The intensity of the green
4
S
3/2
→
4
I
15/2
is much higher compared to the red
4
F
9/2
→
4
I
15/2
emission of Er
3+
. Co-doping Ta
2
O
5
:Er
3+
coatings with sensitizer Yb
3+
ions increased the up-conversion emission PL intensity of Er
3+
thanks to the efficient energy transfer from Yb
3+
to Er
3+
. The red up-conversion PL intensity of
4
F
9/2
→
4
I
15/2
transition increases more rapidly with respect to green emission
4
S
3/2
→
4
I
15/2
. A phonon-assisted energy back transfer process from Er
3+
ions (
4
S
3/2
→
4
I
13/2
) to the neighboring Yb
3+
ions (
2
F
7/2
→
2
F
5/2
) leads to enhanced red emission
4
F
9/2
→
4
I
15
and decreased green emission
4
S
3/2
→
4
I
15/2
.
