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Wang Q.,Nanjing Southeast University | Dong Y.,Nanjing Southeast University | Shao Q.,Nanjing Southeast University | Teng X.,Jiangsu Bree Optronics Co. | And 2 more authors.
Optical Materials | Year: 2017

The thermal degradation is considered as one the most common limitations of Sr2−xEuxSi5N8 nitride phosphors due to the elevated working temperatures in LED. In order to examine the origin of the thermal degradation, Sr2−xEuxSi5N8 was synthesized using high-temperature solid-state reaction. The nitride with activators and the nitride host lattice were studied separately. The diffuse reflectance spectra, the internal quantum efficiency, and optical absorption rate, as well as the element binding energy and element content before and after annealing at high temperature, were investigated. Also, the morphology and surface layers were observed using high-resolution transmission electron microscopy (HRTEM). The results suggested the formation of an amorphous layer on the grain surface, which decreased luminescence efficiency after the heat treatment. It was found that oxidation of both the europium and Sr2Si5N8 host lattice caused the formation of the amorphous layer. © 2017 Elsevier B.V.


Wang Q.,Nanjing Southeast University | Dong Y.,Nanjing Southeast University | Shao Q.,Nanjing Southeast University | Teng X.,Jiangsu Bree Optronics Co. | Jiang J.,Nanjing Southeast University
Materials and Design | Year: 2016

In order to improve photoluminescence properties of the Sr2Si5N8:Eu2+ phosphor, Li3N flux was added into the phosphors and the effect of the Li3N flux on the properties was investigated. The results show that, the amount of Li3N flux had a significantly positive effect on the phosphor properties, such as the particle size, activator occupy site in the crystal lattice and luminescent properties. The emitting integrated intensity of Sr2Si5N8:Eu2+ phosphor was increased by 40%, by selecting the appropriate initial compositions and combustion parameters. Moreover, the phosphor with Li3N flux additions, showed improved heat stability. The improved luminescent properties were attributed to the proper grain size and the increasing N3- concentration during firing. © 2016 Elsevier Ltd.


Shao Q.,Nanjing Southeast University | Dong Y.,Nanjing Southeast University | Jiang J.,Nanjing Southeast University | Liang C.,Jiangsu Bree Optronics Co. | He J.,Jiangsu Bree Optronics Co.
Journal of Luminescence | Year: 2011

The effects of the excitation wavelength, Ce3+ concentration and chemical substitution on the thermal quenching of Y3Al 5O12:Ce3+ (YAG:Ce3+) phosphors were investigated over a temperature range from 30 to 250 °C. The quenching behavior exhibits a complex dependence on the excitation wavelength and Ce 3+ concentration, which can be attributed to temperature-dependent absorption strength of the different fd absorption bands and thermally activated concentration quenching with or without energy migrations between Ce 3+ ions, respectively. With increasing Lu3+content the luminescence of (Y, Lu)3Al5O12:Ce3+ phosphors shows a pronounced blueshift, and simultaneously the temperature quenching is obviously improved due to a decrease in Stokes shift. © 2010 Elsevier B.V. All rights reserved.


Chen Z.,Jiangnan University | Luo J.,Jiangnan University | Liang C.,Jiangsu Bree Optronics Co. | Liu J.L.,Jiangnan University
Applied Mechanics and Materials | Year: 2014

PVP/[Sr(NO3)2+Mg(NO3)2+TEOS+Eu(NO3)2+Dy(NO3)2] composite nanofibers were prepared via electrospinning, the effect of different electrospinning parameters on the composite nanofibers' morphology were investigated. The results revealed that diameter of the composite nanofibers increased at first and then decreased with the increasing of voltage, and the properties of the spinning solution (viscosity and surface tension) increased gradually, but the conductivity decreased at first and then increased with the increasing of PVP content. SEM analysis indicated that it's easy to get a good morphological and uniform composite nanofibers when the voltage was 13 ~ 15 kv, inorganic salt content was 5% ~ 6%, and concentration of PVP was 15%. © (2014) Trans Tech Publications, Switzerland.


Luo J.,Jiangnan University | Liang C.,Jiangsu Bree Optronics Co. | Gao D.-H.,Jiangnan University | Zhang K.-Y.,Jiangnan University
Advanced Materials Research | Year: 2013

The polypropylene luminescent fiber containing Sr2MgSi2O7: Eu2+, Dy3+ phosphors was prepared by melt-spinning method. Crystal phase structure, spectral features and afterglow properties of the luminescent fiber were tested and analyzed. The results show that the fiber has independent superposition phase features of both Sr2MgSi2O7: Eu2+, Dy3+ and polypropylene; the range of its excitation light wavelength locates among 250~450 nm; it can emit blue light of 460 nm wavelength; its initial luminescent intensity is more than 600 mcd/m2, and afterglow time lasts 7 h; the process of afterglow decay consists of fast stage and slow stage. © (2013) Trans Tech Publications, Switzerland.


Teng X.,Jiangsu Bree Optronics Co. | Liang C.,Jiangsu Bree Optronics Co. | He J.,Jiangsu Bree Optronics Co.
Journal of Semiconductors | Year: 2011

The nitride phosphor Sr2Si5N8:Eu 2+ was synthesized by the high temperature solid-state method. The properties of Sr2Si5N8:Eu2+ were discussed by X-ray diffraction (XRD) scanning electron microscope (SEM) and spectra analysis. The XRD pattern shows that the single phase produces when strontium nitride is a bit excessive. The SEM photo implies that the excessive strontium nitride works as a flux in the reaction system. The position of emission peak is also located at about 612 nm as strontium nitride is excessive. The luminescent intensity of the phosphor adding excessive strontium nitride is higher than that of the phosphor introducing stoichiometric strontium nitride. The optimized content of nitride strontium was 2.05 mol/mol for the obtained phosphor with excellent properties.


Jin H.,Nanjing University | Chen Z.-Y.,CAS Hefei Institutes of Physical Science | Yu Q.-Q.,Jiangsu Bree Optronics Company Ltd | Wu S.-S.,Nanjing University
Journal of Thermoplastic Composite Materials | Year: 2016

The C-O, C=O, and C(=O)O groups were introduced onto high-density polyethylene (HDPE) chains by ultraviolet irradiation in air and the groups' content increased with increase in the irradiation time. When they irradiated for 16 h, gels were formed in the irradiated HDPE, and the content of the gels increased with increase in the irradiation time. Compared with HDPE, the crystal form of the irradiated HDPE did not change and still retained the orthorhombic structure, and its melting temperature decreased, while its crystallinity increased. The irradiated HDPE was added in HDPE/CaCO3 composites as a compatibilizer, and HDPE/irradiated HDPE/CaCO3 composites were obtained. Compared with those in HDPE/CaCO3 composites, the dispersion of the CaCO3 and interfacial interaction between CaCO3 and HDPE matrix in HDPE/irradiated HDPE/CaCO3 composites improved due to compatibilization of the irradiated HDPE, and its mechanical properties (especially impact strength), thus, showed remarkable enhancement. With increase in irradiation time, the tensile strength of HDPE/irradiated HDPE/CaCO3 composites enhanced and its impact strength increased during irradiation time of 16 h and then decreased slightly. In the same irradiation time, the tensile strength and impact strength of HDPE/irradiated HDPE/CaCO3 composites increased with increase in the content of the irradiated HDPE. © 2014 The Author(s).


Liang C.,Jiangsu Bree Optronics Co. | You H.,Jiangsu Bree Optronics Co. | Fu Y.,Jiangsu Bree Optronics Co. | Teng X.,Jiangsu Bree Optronics Co. | And 2 more authors.
Dalton Transactions | Year: 2015

CaGdGaAl2O7 and CaGdGaAl2O7:Ce3+,Tb3+ have been synthesized by a traditional solid state reaction for the first time. The Rietveld refinement confirmed that CaGdGaAl2O7 has a tetragonal crystal system with the space group P421m. The photoluminescence properties show that the obtained phosphors can be efficiently excited in the range from 330 to 400 nm, which matches perfectly with commercial UV LED chips. A tunable blue-green emitting CaGdGaAl2O7:Ce3+,Tb3+ phosphor has been obtained, by codoping Ce3+ and Tb3+ ions into the host and varying their relative ratios, and may be a good candidate for blue-green components in UV white LEDs. The luminescence properties and lifetimes reveal an efficient energy transfer from the Ce3+ to Tb3+ ions. The energy transfer is demonstrated to be a dipole-quadrupole mechanism, and the critical distance for Ce3+ to Tb3+ calculated by the concentration quenching is 12.25 Å. © The Royal Society of Chemistry 2015.


Patent
Jiangsu Bree Optronics Co. | Date: 2012-11-28

The present invention discloses a white-light LED red phosphor and method of manufacturing the same. The chemical formula of the phosphor is Ca_(1-y-m-e-r)Y_(y)M_(m)X_(x-p)P_(p)Z_(z)N_(n): Eu_(e), R_(r), wherein 0.001y0.2,0.001m0.2,0.5x,z1.5, 0.001p0.1,2n4,0.01e0.2,0.001r0.1, M is selected from at least one of Sr, Ba, Sc, Li, Na and K; X is selected from at least one of B, Al and Ga, wherein Al is must; Z is selected from Si, V, and Nb, wherein Si is must; R is selected from at least one of Dy, Er, Tm, and Lu, wherein Dy is must. The manufacturing method comprises: Weighing the raw materials according to the chemical formula components in the structural formula (1) and stoichiometric ratio; sealing tightly after mixing them in a protective atmosphere, and then performing segmented roasting in the protective atmosphere adopting the normal-pressure high-temperature solid-state method, finally obtaining the white-light LED red phosphor after post-processing. The phosphor according to the present invention has features such as good chemical stability, high luminous efficiency, and good anti- luminous attenuation performance, etc. Further, this manufacturing method is easy to operate, pollution-free, and low cost.


PubMed | Jiangsu Bree Optronics Co.
Type: Journal Article | Journal: Dalton transactions (Cambridge, England : 2003) | Year: 2015

CaGdGaAl2O7 and CaGdGaAl2O7:Ce(3+),Tb(3+) have been synthesized by a traditional solid state reaction for the first time. The Rietveld refinement confirmed that CaGdGaAl2O7 has a tetragonal crystal system with the space group P4[combining macron]21m. The photoluminescence properties show that the obtained phosphors can be efficiently excited in the range from 330 to 400 nm, which matches perfectly with commercial UV LED chips. A tunable blue-green emitting CaGdGaAl2O7:Ce(3+),Tb(3+) phosphor has been obtained, by codoping Ce(3+) and Tb(3+) ions into the host and varying their relative ratios, and may be a good candidate for blue-green components in UV white LEDs. The luminescence properties and lifetimes reveal an efficient energy transfer from the Ce(3+) to Tb(3+) ions. The energy transfer is demonstrated to be a dipole-quadrupole mechanism, and the critical distance for Ce(3+) to Tb(3+) calculated by the concentration quenching is 12.25 .

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