The synthesis of co-doped KEu0.01Gd0.19Yb0.8(WO4)2 was achieved by a modified Pechini method at 750℃. The structure of obtained compound was confirmed using X-ray diffraction measurement and Raman spectroscopy. Th...The synthesis of co-doped KEu0.01Gd0.19Yb0.8(WO4)2 was achieved by a modified Pechini method at 750℃. The structure of obtained compound was confirmed using X-ray diffraction measurement and Raman spectroscopy. The Scherrer's formula was used to confirm the grain sizes visualized by TEM technique. The grain sizes of about 100 nm of monoclinic KGW were successfully obtained by this meth- odology. In order to study spectroscopic properties of the prepared system the emission spectra were measured. The effective down- and up-conversion processes in non-resonant system were investigated.展开更多
The Tb3+-doped Y2O3 nanopowders were synthesized using the modified Pechini method. The average size of nanocrystaUites was controlled by different sintering temperatures. The structure and morphology of obtained nan...The Tb3+-doped Y2O3 nanopowders were synthesized using the modified Pechini method. The average size of nanocrystaUites was controlled by different sintering temperatures. The structure and morphology of obtained nanopowders were examined using the XRD and SEM analyses. The Cr:Al2O3 was mixed with Th3+:Y2O3 powders and its normalized emission was used. to measure a relative intensity of Tb3+:Y2O3. The mixtures were electrophoretically deposited on ITO-glass slides. The cathodoluminescence spectra of obtained layers were recorded and analysed. The discussion over an influence of average grains size on phosphor efficiency was presented.展开更多
The paper dealt with the study of fluorescence properties of sol-gel systems doped with rate-earth ions and co-doped with silver. The general problem for these types of inorganic phosphors was a very low absorbance in...The paper dealt with the study of fluorescence properties of sol-gel systems doped with rate-earth ions and co-doped with silver. The general problem for these types of inorganic phosphors was a very low absorbance in the visible range. Therefore, a sensitizer of luminescence of the rare-earth ions should be selected and used. The sensitizer should possess a good absorbance in the visible range and strong interaction with the rare-earth ions. In this study silver ions were selected as the sensitizer.展开更多
The electric measurements were carried out for La0.8Sr0.2CoO3 nanoceramics by using impedance spectroscopy methods. The resistance of sample was practically independent of frequency in measurement range. Its dependenc...The electric measurements were carried out for La0.8Sr0.2CoO3 nanoceramics by using impedance spectroscopy methods. The resistance of sample was practically independent of frequency in measurement range. Its dependence on reciprocal temperature showed quite complicated mechanism of conduction. The most striking property of investigated sample was its resistance decreasing with increasing applied polarization.展开更多
Absorption, excitation and emission spectra as well as decay time measurements at 10, 77, and 300 K were perfumed for Gd3Sc2Ga3O12 garnet single-crystal doped with Cr^3+ and Nd^3+ ions. Strong reabsorption of Cr3+ ...Absorption, excitation and emission spectra as well as decay time measurements at 10, 77, and 300 K were perfumed for Gd3Sc2Ga3O12 garnet single-crystal doped with Cr^3+ and Nd^3+ ions. Strong reabsorption of Cr3+ emission by Nd3+ absorption lines was ob- served. The assignments of f-f and d-d transitions were proposed. The broad emission band of chromium ions is an indication that weak/intermediate crystal field strength is present at the Cr3+ site.展开更多
La1-xSrxMnO3-δ was synthesized by the Pechini's method. The XRD pattern and TEM indicate the formation of the perovskite without the presence of secondary phases. It was found that La0.8Sr0.2MnO3-δsample prepared a...La1-xSrxMnO3-δ was synthesized by the Pechini's method. The XRD pattern and TEM indicate the formation of the perovskite without the presence of secondary phases. It was found that La0.8Sr0.2MnO3-δsample prepared at 1000℃ in air atmospheres, contains about 13.11% of the manganese as Mn4+ and 86.89% of the manganese as Mn3+. The electric measurements were carded out for La0.8Sr0.2MnO3-δ nanoceramics by using impedance spectroscopy methods and found to be 0.1 S/cm at 250 ℃ similar to the typical value of La0.8Sr0.2MnO3-δ materials. Its dependence on reciprocal temperature shows quite complicated mechanism of conduction.展开更多
Eu^3+doped TiO2 anatase spheres were obtained by modified sol-gel approach.Spheres(110-250 nm)are composed of smaller(5-15 nm)nanocrystals and exhibit red emission under UV light excitation.Materials were synthesized ...Eu^3+doped TiO2 anatase spheres were obtained by modified sol-gel approach.Spheres(110-250 nm)are composed of smaller(5-15 nm)nanocrystals and exhibit red emission under UV light excitation.Materials were synthesized by multi-step method from glycolated titania alkoxides.Europium doped(1.0 mol%)and non-doped spheres were synthesized.Their optical and structural properties were compared by materials characterization methods,such as X-ray powder diffraction,transmission electron microscopy and PL spectroscopy.Doped TiO2 spheres are crystalline phase pure and exhibit high luminescence intensity.展开更多
Europium orthophosphate monohydrate (EuPO4·H2O) nanorods with typical dimensions of about 10-30 nm in diameter and 300-500 nm in length were prepared by using the soft template method. The effects of using diet...Europium orthophosphate monohydrate (EuPO4·H2O) nanorods with typical dimensions of about 10-30 nm in diameter and 300-500 nm in length were prepared by using the soft template method. The effects of using diethylene glycol (DEG) and polyethylene glycol (PEG) polymers as well as the pH values on the size, crystalline structure and morphology of EuPO4·H2O nanorods were investigated. Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) data of the prepared samples were elucidated. The nanorods were highly uniform and their mean length was reduced by using DEG and PEG as soft template agents. For all prepared samples, the rhabdophanetype hexagonal EuPO4·H2O was the dominated phase. The photoluminescence (PL) spectroscopy measurements of EuPO4·H2O nanorods revealed that, under UV excitation, EuPO4·H2O nanorods exhibited strong luminescence with narrow bands corresponding to the intra-4f transitions of ^5D0→^7Fj (j=1, 2, 3, 4) of Eu^3+ ions. The peaks were found at 594 nm (^5D0→^7F1), 619 nm (^5D0→^7F2), 652 nm (^5D0→^7F3), and 697 nm (^5D0→^7F4), with the strongest emission at 594 nm.展开更多
The magnetization measurements of gallium nitride nanoceramics doped with 1% of cerium and sintered under various pressures were reported. It was found that GaN nanoceramics doped with cerium showed paramagnetic behav...The magnetization measurements of gallium nitride nanoceramics doped with 1% of cerium and sintered under various pressures were reported. It was found that GaN nanoceramics doped with cerium showed paramagnetic behavior in the wide temperature range. Nanoceramics of GaN with 1% of Ce (as undoped GaN) was diamagnetic one, but under certain temperature the paramagnetic properties started to dominate. This crossover temperature was nonlinearly dependent on the pressure applied during the sintering. The fitting of molar magnetic susceptibility allowed to estimate the Curie temperature, Curie constant and diamagnetic part of susceptibility. As it was found, all the samples showed the antiferromagnetic ordering with θp≈-1 K. Also, the effective magnetic moment was estimated for all of the samples. As a result, magnetic moments in terms of Ce ion were notably larger in comparison with those obtained within the Russell-Saunders cou- pling model. We suggested that it was the strong influence of amorphous shell which was rising with the pressure applied during the sintering. Finally, we presented dependences of magnetization as a function of applied field. All the samples manifested weak ferromagnetism at high temperatures and paramagnetic behavior in low temperature region.展开更多
Spectroscopic properties of tetragonal LiYbF_4 nanocrystals under high dense NIR excitation at vacuum condition were investigated. White, broad band emission covering whole visible part of the spectrum from LiYbF_4 na...Spectroscopic properties of tetragonal LiYbF_4 nanocrystals under high dense NIR excitation at vacuum condition were investigated. White, broad band emission covering whole visible part of the spectrum from LiYbF_4 nanocrystals was observed. Its intensity strongly depended on the excitation power, excitation wavelength and ambient pressure. Temperature of the nanocrystals under 975 nm excitation was determined as a function of excitation power. Strong photo-induced current was observed from LiYbF_4 pallet. The emission kinetic was analyzed. The mechanism of the anti-Stokes white emission was discussed in terms of the laser-induced charge transfer emission from Yb^(2+) states.展开更多
Transparent, luminescent and functional nanocomposites demonstrate interesting optical and mechanical properties suitable for many optoelectronic applications. Transparent polymethyl methacrylate (PMMA) polymer nano...Transparent, luminescent and functional nanocomposites demonstrate interesting optical and mechanical properties suitable for many optoelectronic applications. Transparent polymethyl methacrylate (PMMA) polymer nanocornposites modified with thenoyl- trifluoroacetonate (TAA) were fabricated by in situ polymerization and used as hosts for homogenous dispersion of 3 mol.% Eu^3+:Ca10(PO4)6(OH)2 (Eu^3+:HA) hydroxyapatite -20 nm large nanocrystals. The emission, excitation and transmission spectra as well as the fluorescence decay rates of bare Eu^3+:HA nanocrystallites, Eu^3+:HA embedded in the PMMA and and Eu:HA embedded in the PMMA/TTA rtanocomposites were studied. The improvement of transparency was demonstrated with the addition of TTA as well as europium doped hydroxyapatites in comparison to pure PMMA matrix. The Judd-Ofelt analysis of f-f transitions of Eu^3+:HA nanocrystallites, the PMMA/Eu^3+:HA and the PMMA+TTA/Eu^3+:HA was performed to investigate the optical behavior of the polymeric composites.展开更多
Tb3+-doped ZnSe and ZnSe/ZnS nanocrystals were synthesized using modified hot-injection method. The observation of the characteristic quantum dots absorption features in a time-gated excitation spectrum was recorded ...Tb3+-doped ZnSe and ZnSe/ZnS nanocrystals were synthesized using modified hot-injection method. The observation of the characteristic quantum dots absorption features in a time-gated excitation spectrum was recorded while monitoring Tb3+ emission at 545 nm provided direct evidence for successful incorporation of dopant ions into semiconductor host. Relatively long decay time (-1.5 ms) of Tb3+ emission indicated that dopant ions were well protected from interaction with surface ligands. Emission properties of core ZnSe:Tb3+ nanocrystals were only slightly modified upon growth of ZnS shell.展开更多
The yellow emitting dysprosium oxysulfide (Dy2O2S) and dysprosium oxysulfate (Dy202SO4) compounds were prepared from the thermal decomposition of hydrated dysprosium sulphate. The materials were characterized by u...The yellow emitting dysprosium oxysulfide (Dy2O2S) and dysprosium oxysulfate (Dy202SO4) compounds were prepared from the thermal decomposition of hydrated dysprosium sulphate. The materials were characterized by using thermogravimetry (TG/DTG), X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopies. The thermal stability temperatures at around 1151 and 1313 K were determined for the Dy202S and Dy202SO4 materials, respectively. The photolumines- cence properties of the dysprosium oxysulfide were investigated, showing narrow emission bands assigned to the 4F9/2----*6HJ intracon- figurational transitions of the Dy3+ ion. The yellow emission color of this phosphor suggests that the Dy202S is a promising material for applications in LEDs.展开更多
In this article,varied praseodymium polyphosphate hosts:MI(Li,Na K)Pr(PO3)4 microcrystals and LiLa1-xPrx(PO3)4(x = 0.01 ^-1)nanocrystals were successfully synthesized by the flux method and the coprecipitation techniq...In this article,varied praseodymium polyphosphate hosts:MI(Li,Na K)Pr(PO3)4 microcrystals and LiLa1-xPrx(PO3)4(x = 0.01 ^-1)nanocrystals were successfully synthesized by the flux method and the coprecipitation technique,respectively.The size of stoichiometric nanocrystals of LiPr(PO3)4 was tuned by the te mpe rature of thermal treatment in range of 35-145 nm.In order to dete rmine the most suitable material for the non-contact optical thermometric applications,the temperature sensing measurements were carried out by using luminescence intensity ratio(LIR)of emission bands corresponding to the ^3 P1→ ^3H5 and ^3P0→ ^3 H5 electronic transitions of Pr3+ ions into the 123-423 K temperature range.The influence of the host material composition of MⅠ(Li,Na,K)Pr(PO3)4 microcrystals on the sensitivity of luminescent thermometers was studied.It is found that the sensitivity of lithium praseodymium polyphosphate is the highest of all micropowders under investigation.Moreover,it is found that the nanocrystals reveal much higher relative sensitivity in respect to the microcrystalline counterparts.The highest sensitivity of LIR temperature sensing is found for LiPr(PO3)4 nanocrystals(35 nm grain size)in the whole temperature range,reaching 0.283%/K at 164 K.The impact of the average grain size on the sensitivity of LIR based thermometers of LiPr(PO3)4 nanocrystals was investigated.It is found that the reduction of the grain size from 145 to 35 nm results in the enhancement of the relative sensitivity from0.156 to 0.240%/K at 223 K.Additionally it is found that the high dopant concentration possesses favorable influence on the relative sensitivity of LiLa1-xPrx(PO3)4 nanocrystalline luminescent thermometers.展开更多
In the present work, a sol-gel method was employed to prepare nanosized SrAl2O4 powders doped with Eu3+ions. The raw nano- materials were thermally treated at 900 to 1100℃ for 3 h. The XRD analysis demonstrated that...In the present work, a sol-gel method was employed to prepare nanosized SrAl2O4 powders doped with Eu3+ions. The raw nano- materials were thermally treated at 900 to 1100℃ for 3 h. The XRD analysis demonstrated that the powders were single-phase nanopowders with high crystallite dispersion. Our studies were focused on relating the luminescence properties of the Eu^3+ dopant to the NC (nanocrystallites) size. This was achieved by varying the calcinations temperature between 900 and 1100 ℃. The average NC size varied accordingly between -36 and -75 nm. We found that size effect manifested mainly in the expansion of the cell volume and broadening of XRD peaks as indicated by Rietveld analysis. Moreover the emission and excitation spectra, although typical for Eu^3+ ions, demonstrated some degree of variability with calcinations temperature and doping concentration. To explain these differences a detailed analysis of luminescence spectra by the Judd-Ofelt theory was performed.展开更多
This paper discusses the possibility of synthesis of SBTL sol-gel films for use as active layers for non-volatile memory (FRAM). La-doped SrBi2Ta209 thin films were synthesized by sol-gel method on Pt/TiO2/BPSG/SiO2...This paper discusses the possibility of synthesis of SBTL sol-gel films for use as active layers for non-volatile memory (FRAM). La-doped SrBi2Ta209 thin films were synthesized by sol-gel method on Pt/TiO2/BPSG/SiO2/Si substrates. The structural features of the surface (AFM), crystallization behavior (XRD) during the heating and ferroelectric properties of synthesized films were discussed. It was shown that an optimum surface structure and a high share of perovskite phase of SBTL-films were compared to SBT-films (Theating=800 ℃). Achieved ferroelectric parameters suggested the possibility of using synthesized SBTL sol-gel films in non-volatile memory devices.展开更多
文摘The synthesis of co-doped KEu0.01Gd0.19Yb0.8(WO4)2 was achieved by a modified Pechini method at 750℃. The structure of obtained compound was confirmed using X-ray diffraction measurement and Raman spectroscopy. The Scherrer's formula was used to confirm the grain sizes visualized by TEM technique. The grain sizes of about 100 nm of monoclinic KGW were successfully obtained by this meth- odology. In order to study spectroscopic properties of the prepared system the emission spectra were measured. The effective down- and up-conversion processes in non-resonant system were investigated.
基金supported by the Polish Ministry of Sciences and Higher Education (N507 076 32/2186)
文摘The Tb3+-doped Y2O3 nanopowders were synthesized using the modified Pechini method. The average size of nanocrystaUites was controlled by different sintering temperatures. The structure and morphology of obtained nanopowders were examined using the XRD and SEM analyses. The Cr:Al2O3 was mixed with Th3+:Y2O3 powders and its normalized emission was used. to measure a relative intensity of Tb3+:Y2O3. The mixtures were electrophoretically deposited on ITO-glass slides. The cathodoluminescence spectra of obtained layers were recorded and analysed. The discussion over an influence of average grains size on phosphor efficiency was presented.
文摘The paper dealt with the study of fluorescence properties of sol-gel systems doped with rate-earth ions and co-doped with silver. The general problem for these types of inorganic phosphors was a very low absorbance in the visible range. Therefore, a sensitizer of luminescence of the rare-earth ions should be selected and used. The sensitizer should possess a good absorbance in the visible range and strong interaction with the rare-earth ions. In this study silver ions were selected as the sensitizer.
文摘The electric measurements were carried out for La0.8Sr0.2CoO3 nanoceramics by using impedance spectroscopy methods. The resistance of sample was practically independent of frequency in measurement range. Its dependence on reciprocal temperature showed quite complicated mechanism of conduction. The most striking property of investigated sample was its resistance decreasing with increasing applied polarization.
基金supported by Ministry of Science and Higher Education (N N507 372335)
文摘Absorption, excitation and emission spectra as well as decay time measurements at 10, 77, and 300 K were perfumed for Gd3Sc2Ga3O12 garnet single-crystal doped with Cr^3+ and Nd^3+ ions. Strong reabsorption of Cr3+ emission by Nd3+ absorption lines was ob- served. The assignments of f-f and d-d transitions were proposed. The broad emission band of chromium ions is an indication that weak/intermediate crystal field strength is present at the Cr3+ site.
基金supported by Bilateral S & T Cooperation between the Hellenic Republic and the Republic of Poland (2005-2007)
文摘La1-xSrxMnO3-δ was synthesized by the Pechini's method. The XRD pattern and TEM indicate the formation of the perovskite without the presence of secondary phases. It was found that La0.8Sr0.2MnO3-δsample prepared at 1000℃ in air atmospheres, contains about 13.11% of the manganese as Mn4+ and 86.89% of the manganese as Mn3+. The electric measurements were carded out for La0.8Sr0.2MnO3-δ nanoceramics by using impedance spectroscopy methods and found to be 0.1 S/cm at 250 ℃ similar to the typical value of La0.8Sr0.2MnO3-δ materials. Its dependence on reciprocal temperature shows quite complicated mechanism of conduction.
文摘Eu^3+doped TiO2 anatase spheres were obtained by modified sol-gel approach.Spheres(110-250 nm)are composed of smaller(5-15 nm)nanocrystals and exhibit red emission under UV light excitation.Materials were synthesized by multi-step method from glycolated titania alkoxides.Europium doped(1.0 mol%)and non-doped spheres were synthesized.Their optical and structural properties were compared by materials characterization methods,such as X-ray powder diffraction,transmission electron microscopy and PL spectroscopy.Doped TiO2 spheres are crystalline phase pure and exhibit high luminescence intensity.
基金Project supported by Vietnam's National Foundation for Science and Technology Development (103.06.46.09)
文摘Europium orthophosphate monohydrate (EuPO4·H2O) nanorods with typical dimensions of about 10-30 nm in diameter and 300-500 nm in length were prepared by using the soft template method. The effects of using diethylene glycol (DEG) and polyethylene glycol (PEG) polymers as well as the pH values on the size, crystalline structure and morphology of EuPO4·H2O nanorods were investigated. Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) data of the prepared samples were elucidated. The nanorods were highly uniform and their mean length was reduced by using DEG and PEG as soft template agents. For all prepared samples, the rhabdophanetype hexagonal EuPO4·H2O was the dominated phase. The photoluminescence (PL) spectroscopy measurements of EuPO4·H2O nanorods revealed that, under UV excitation, EuPO4·H2O nanorods exhibited strong luminescence with narrow bands corresponding to the intra-4f transitions of ^5D0→^7Fj (j=1, 2, 3, 4) of Eu^3+ ions. The peaks were found at 594 nm (^5D0→^7F1), 619 nm (^5D0→^7F2), 652 nm (^5D0→^7F3), and 697 nm (^5D0→^7F4), with the strongest emission at 594 nm.
基金Project supported by Wroclaw Research Centre EIT (WCB/3/I/2010)
文摘The magnetization measurements of gallium nitride nanoceramics doped with 1% of cerium and sintered under various pressures were reported. It was found that GaN nanoceramics doped with cerium showed paramagnetic behavior in the wide temperature range. Nanoceramics of GaN with 1% of Ce (as undoped GaN) was diamagnetic one, but under certain temperature the paramagnetic properties started to dominate. This crossover temperature was nonlinearly dependent on the pressure applied during the sintering. The fitting of molar magnetic susceptibility allowed to estimate the Curie temperature, Curie constant and diamagnetic part of susceptibility. As it was found, all the samples showed the antiferromagnetic ordering with θp≈-1 K. Also, the effective magnetic moment was estimated for all of the samples. As a result, magnetic moments in terms of Ce ion were notably larger in comparison with those obtained within the Russell-Saunders cou- pling model. We suggested that it was the strong influence of amorphous shell which was rising with the pressure applied during the sintering. Finally, we presented dependences of magnetization as a function of applied field. All the samples manifested weak ferromagnetism at high temperatures and paramagnetic behavior in low temperature region.
基金supported by National Centre of Science(NCS)Project(Poland)(NCN-2012/06/A/ST5/00212)
文摘Spectroscopic properties of tetragonal LiYbF_4 nanocrystals under high dense NIR excitation at vacuum condition were investigated. White, broad band emission covering whole visible part of the spectrum from LiYbF_4 nanocrystals was observed. Its intensity strongly depended on the excitation power, excitation wavelength and ambient pressure. Temperature of the nanocrystals under 975 nm excitation was determined as a function of excitation power. Strong photo-induced current was observed from LiYbF_4 pallet. The emission kinetic was analyzed. The mechanism of the anti-Stokes white emission was discussed in terms of the laser-induced charge transfer emission from Yb^(2+) states.
基金Project supported by Polish Ministry of National Education (N N507 584938)
文摘Transparent, luminescent and functional nanocomposites demonstrate interesting optical and mechanical properties suitable for many optoelectronic applications. Transparent polymethyl methacrylate (PMMA) polymer nanocornposites modified with thenoyl- trifluoroacetonate (TAA) were fabricated by in situ polymerization and used as hosts for homogenous dispersion of 3 mol.% Eu^3+:Ca10(PO4)6(OH)2 (Eu^3+:HA) hydroxyapatite -20 nm large nanocrystals. The emission, excitation and transmission spectra as well as the fluorescence decay rates of bare Eu^3+:HA nanocrystallites, Eu^3+:HA embedded in the PMMA and and Eu:HA embedded in the PMMA/TTA rtanocomposites were studied. The improvement of transparency was demonstrated with the addition of TTA as well as europium doped hydroxyapatites in comparison to pure PMMA matrix. The Judd-Ofelt analysis of f-f transitions of Eu^3+:HA nanocrystallites, the PMMA/Eu^3+:HA and the PMMA+TTA/Eu^3+:HA was performed to investigate the optical behavior of the polymeric composites.
基金Project supported by Wroclaw Research Centre EIT+within the project"The Application of Nanotechnology in Advanced Materials”-Nano Mat(POIG.01.01.02-02-002/08) co-financed by the European Regional Development Fund(Operational Programme Innovative Economy,1.1.2)
文摘Tb3+-doped ZnSe and ZnSe/ZnS nanocrystals were synthesized using modified hot-injection method. The observation of the characteristic quantum dots absorption features in a time-gated excitation spectrum was recorded while monitoring Tb3+ emission at 545 nm provided direct evidence for successful incorporation of dopant ions into semiconductor host. Relatively long decay time (-1.5 ms) of Tb3+ emission indicated that dopant ions were well protected from interaction with surface ligands. Emission properties of core ZnSe:Tb3+ nanocrystals were only slightly modified upon growth of ZnS shell.
基金Project supported by Higher Education Personnel Improvement Coordination(CAPES)the National Council for Scientific and Technological Development(CNPq)+2 种基金the Laboratory of Thermal Analysis Prof.Ivo Giolito(LATIG-USP)Laboratory of f-block Elements(Leb-f)USPInstitute of Low Temperature and Structure Research and the Polish Academy of Sciences
文摘The yellow emitting dysprosium oxysulfide (Dy2O2S) and dysprosium oxysulfate (Dy202SO4) compounds were prepared from the thermal decomposition of hydrated dysprosium sulphate. The materials were characterized by using thermogravimetry (TG/DTG), X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopies. The thermal stability temperatures at around 1151 and 1313 K were determined for the Dy202S and Dy202SO4 materials, respectively. The photolumines- cence properties of the dysprosium oxysulfide were investigated, showing narrow emission bands assigned to the 4F9/2----*6HJ intracon- figurational transitions of the Dy3+ ion. The yellow emission color of this phosphor suggests that the Dy202S is a promising material for applications in LEDs.
基金Project supported by the Ministry of Higher Education and Scientific Research in Tunisia(99/UR/07-03)
文摘In this article,varied praseodymium polyphosphate hosts:MI(Li,Na K)Pr(PO3)4 microcrystals and LiLa1-xPrx(PO3)4(x = 0.01 ^-1)nanocrystals were successfully synthesized by the flux method and the coprecipitation technique,respectively.The size of stoichiometric nanocrystals of LiPr(PO3)4 was tuned by the te mpe rature of thermal treatment in range of 35-145 nm.In order to dete rmine the most suitable material for the non-contact optical thermometric applications,the temperature sensing measurements were carried out by using luminescence intensity ratio(LIR)of emission bands corresponding to the ^3 P1→ ^3H5 and ^3P0→ ^3 H5 electronic transitions of Pr3+ ions into the 123-423 K temperature range.The influence of the host material composition of MⅠ(Li,Na,K)Pr(PO3)4 microcrystals on the sensitivity of luminescent thermometers was studied.It is found that the sensitivity of lithium praseodymium polyphosphate is the highest of all micropowders under investigation.Moreover,it is found that the nanocrystals reveal much higher relative sensitivity in respect to the microcrystalline counterparts.The highest sensitivity of LIR temperature sensing is found for LiPr(PO3)4 nanocrystals(35 nm grain size)in the whole temperature range,reaching 0.283%/K at 164 K.The impact of the average grain size on the sensitivity of LIR based thermometers of LiPr(PO3)4 nanocrystals was investigated.It is found that the reduction of the grain size from 145 to 35 nm results in the enhancement of the relative sensitivity from0.156 to 0.240%/K at 223 K.Additionally it is found that the high dopant concentration possesses favorable influence on the relative sensitivity of LiLa1-xPrx(PO3)4 nanocrystalline luminescent thermometers.
基金Project supported by the Polish Ministry of Science and Higher Education (NN 204331537)National Science Centre (N N507 372335)
文摘In the present work, a sol-gel method was employed to prepare nanosized SrAl2O4 powders doped with Eu3+ions. The raw nano- materials were thermally treated at 900 to 1100℃ for 3 h. The XRD analysis demonstrated that the powders were single-phase nanopowders with high crystallite dispersion. Our studies were focused on relating the luminescence properties of the Eu^3+ dopant to the NC (nanocrystallites) size. This was achieved by varying the calcinations temperature between 900 and 1100 ℃. The average NC size varied accordingly between -36 and -75 nm. We found that size effect manifested mainly in the expansion of the cell volume and broadening of XRD peaks as indicated by Rietveld analysis. Moreover the emission and excitation spectra, although typical for Eu^3+ ions, demonstrated some degree of variability with calcinations temperature and doping concentration. To explain these differences a detailed analysis of luminescence spectra by the Judd-Ofelt theory was performed.
文摘This paper discusses the possibility of synthesis of SBTL sol-gel films for use as active layers for non-volatile memory (FRAM). La-doped SrBi2Ta209 thin films were synthesized by sol-gel method on Pt/TiO2/BPSG/SiO2/Si substrates. The structural features of the surface (AFM), crystallization behavior (XRD) during the heating and ferroelectric properties of synthesized films were discussed. It was shown that an optimum surface structure and a high share of perovskite phase of SBTL-films were compared to SBT-films (Theating=800 ℃). Achieved ferroelectric parameters suggested the possibility of using synthesized SBTL sol-gel films in non-volatile memory devices.