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
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
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
Downshifting behavior of the Tb3＋-gb3＋ co-doped nanocrystalline LiLaP4012 powders synthesized by co-precipitation method was presented and discussed. The structural phase purity of obtained material was confirmed by...Downshifting behavior of the Tb3＋-gb3＋ co-doped nanocrystalline LiLaP4012 powders synthesized by co-precipitation method was presented and discussed. The structural phase purity of obtained material was confirmed by X-ray diffraction （XRD） measurements. Strong enhancement of ytterbium 2 2 - 3＋ F5/2- F7/2 emission intensity was observed with decreasing Tb concentration un- der UV excitation. Dependence of efficiency of energy transfer between dopants on pumping wavelength was investigated due to bet- ter understanding of down-shifting mechanism. It was found that luminescence intensity of Yb3＋ decreased above 10 tool.% dopant con- tent, what was caused by concentration quenching. The power dependence measurements were carried out at 77 and 300 K. The re- sulting slopes had the same value of 1, what indicated the existence of linear down-shifting process, independent of the temperature.展开更多
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 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 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.
文摘Downshifting behavior of the Tb3＋-gb3＋ co-doped nanocrystalline LiLaP4012 powders synthesized by co-precipitation method was presented and discussed. The structural phase purity of obtained material was confirmed by X-ray diffraction （XRD） measurements. Strong enhancement of ytterbium 2 2 - 3＋ F5/2- F7/2 emission intensity was observed with decreasing Tb concentration un- der UV excitation. Dependence of efficiency of energy transfer between dopants on pumping wavelength was investigated due to bet- ter understanding of down-shifting mechanism. It was found that luminescence intensity of Yb3＋ decreased above 10 tool.% dopant con- tent, what was caused by concentration quenching. The power dependence measurements were carried out at 77 and 300 K. The re- sulting slopes had the same value of 1, what indicated the existence of linear down-shifting process, independent of the temperature.
