CN105670624A

CN105670624A - Fluorescent powder capable of realizing blue light-white light conversion based on ultraviolet excitation and preparation method of fluorescent powder

Info

Publication number: CN105670624A
Application number: CN201610051485.6A
Authority: CN
Inventors: 姜锋; 朱德生
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2016-01-26
Filing date: 2016-01-26
Publication date: 2016-06-15
Anticipated expiration: 2036-01-26
Also published as: CN105670624B

Abstract

The invention discloses fluorescent powder capable of realizing blue light-white light conversion based on ultraviolet excitation and a preparation method of the fluorescent powder. The fluorescent powder has a chemical formula of Sr(1-n)(WO4)(1-x)Cl2x:nEu, is a single-phase luminescent material and has three luminescence centers of WO4<2->, Eu<2+> and Eu<3+>, n and X are mole numbers, X is larger than 0 and smaller than 0.03, and n is larger than or equal to 0.03 and smaller than or equal to 0.15. The single fluorescent powder can emit blue light and white light under the excitation of ultraviolet light with different wavelengths; the emitted white light and blue light both have good stability and light emitting characteristics.

Description

A kind of based on blue light under burst of ultraviolel-white light conversion phosphor and preparation method thereof

Technical field

The present invention relates to luminescent material technical field, be specifically related to a kind of blue light-white light conversion phosphor and preparation method thereof.

Background technology

Tungstates, as a kind of stable luminescent property, has excellent excitation and stablizes the self-activation fluorescent material of chemical property, being constantly subjected to the extensive concern of domestic and international researcher. Increasingly mature along with White light LED technology, finds colory fluorescent material and becomes more and more important, and with tungstates for substrate, rare earth ion is the emphasis that the fluorescent material of the centre of luminescence becomes research naturally. In order to study the character of the luminescent material being substrate with strontium tungstate, the research of history is concentrated mainly on three aspects. First is the character of strontium tungstate itself, and such as glitter, the growth mechanism of crystal and optical characteristics, vibrational spectrum and thermal property and synthesis control etc., the stability study that this kind of research is substrate lays a solid foundation. Second aspect is cation doping, and namely strontium ion is partly by other ionic replacement such as Ca, to obtain more reasonable structure, the centre of luminescence helps optimization substrate that is bigger or that carry out photocontrol. Certainly, the luminosity of fluorescent material is mainly determined by its centre of luminescence, the centre of luminescence determines the color of material emission, brightness, purity etc., rare-earth cation has the 4f5d electron configuration by external world's shielding of underfill, 4f electronics can within f-f configuration or transition between f-d configuration, there is abundant electron energy level and long-life excited state, the light wave of various wavelength from ultraviolet to infrared light district can be launched, therefore, the research being the centre of luminescence with rare-earth cation becomes in all research aspects form the most widely. Eu³⁺Luminescence is concentrated mainly on region of red light, receives diversified research because of the needs of white light LEDs, such as by molten-salt growth method, ethylene glycol, microwave method, solid phase method, sol-gel process etc., powder body is synthesized. Additionally, with strontium tungstate for substrate, with Tm³⁺、Yb³⁺、Pr³⁺、Tb³⁺、Nd³⁺、Sm³⁺The luminescent material that plasma is the centre of luminescence have also been obtained research.

Summary of the invention

It is an object of the invention to provide a kind of single-component phosphor, it is possible under different wave length ultraviolet excitation, send blue light and white light; And the white light sent out, blue light are respectively provided with good stability and luminescence feature.

The preparation method that another object of the present invention aims to provide above-mentioned fluorescent material.

The one of the present invention is based on blue light under burst of ultraviolel-white light conversion phosphor, and its chemical formula is Sr_1-n(WO₄)_1-xCl_2x: nEu fluorescent material is single-phase luminescent material, has WO₄ ^2-、Eu²⁺And Eu³⁺Three centres of luminescence, n, X are molal quantity, 0 < X < 0.03,0.03≤n≤0.15.

The present invention is 0.01≤X < 0.03 preferably. The preferred version of the present invention also includes 0.01≤X≤0.02.

The present invention is 0.05≤n≤0.1 preferably.

The present invention based on blue light under burst of ultraviolel-white light conversion phosphor, be under the ultraviolet excitation of 240～260nm, fluorescent material blue light-emitting; Under the ultraviolet excitation of 266～300nm, fluorescent material emits white light. Preferred implementation process is under the ultraviolet excitation of 250nm, fluorescent material blue light-emitting; Under the ultraviolet excitation of 294, fluorescent material emits white light.

The preparation method based on white light-white light conversion phosphor blue under burst of ultraviolel of the present invention, described fluorescent material is to be synthesized by high temperature solid state reaction in air atmosphere by the raw material preparing fluorescent material; Described high temperature is 800 DEG C～950 DEG C.

Described phosphor raw material is: strontium carbonate, ammonium metatungstate, ammonium chloride and europium oxide, by generating Sr_1-n(WO₄)_1-xCl_2x: the stoichiometric proportion preparation needed for nEu is ground, and high temperature solid state reaction synthesizes.

The currently preferred high temperature solid state reaction time is 1～4 hour.

Advantages of the present invention and effect are in that: the Sr of the present invention_1-n(WO₄)_1-xCl_2x: nEu fluorescent material is single-phase luminescent material, and granule is uniform, and this luminescent material has WO₄ ^2-、Eu²⁺、Eu³⁺Three centres of luminescence, work as Cl^-When concentration is relatively low, three centres of luminescence are simultaneously luminous, and in blueness under 250nm burst of ultraviolel, fluorescent material is with Cl^-The increase of concentration is close to white light field by blue light, and colour temperature is high; Excite at 294nm and issue out colory white light; When x is between 0.01 and 0.03, the fluorescent material of body series has good blue light and white-light emitting effect, time particularly between 0.01 and 0.02, it is possible to maintain blue light and the white-light emitting effect of the best; When x >=0.03, Eu³⁺Ion concentration is not enough to show its emission spectrum. System has three centres of luminescence, is WO42-, Eu respectively²⁺And Eu³⁺, there is outstanding luminescent quality, it is possible to as the blue emitting phosphor of specific use, it is also possible to separately as the potential succedaneum of white light LEDs.

The advantage of the preparation method of the present invention is in that, adopts high temperature solid-state method to synthesize Sr_1-n(WO₄)_1-xCl_2x: nEu fluorescent material, for single-phase luminescent material. Cl^-Addition by part Eu³⁺It is reduced to Eu²⁺, production process completes in air atmosphere, it is not necessary to add protective gas or reducing gas or other reducing agent. Obtained fluorescent powder grain is uniform, it does not have a large amount of powder agglomeration phenomenons.

Accompanying drawing explanation

Fig. 1 is the Sr of Solid phase synthesis_0.95(WO₄)_1-xCl_2x: the XRD figure of 0.05Eu.

Fig. 2 is N3 sample Sr_0.95(WO₄)_0.98Cl_0.04: the SEM figure of 0.05Eu.

Fig. 3 is the excitation and emission spectra figure of N2 sample.

Fig. 4 is different Cl^-The excitation spectrum of content and emission spectrum figure. Wherein (a) is the 397nm excitation spectrum monitoring wavelength, b emission spectrum Waterfall plot that () is 250nm excitation wavelength, c () monitors the excitation spectrum of wavelength for 616nm, (d) is the emission spectrum Waterfall plot of the series of samples that 294nm wavelength excites.

Fig. 5 is the emission spectrum (λ of N5 and N6_ex=281nm) figure.

The Sr of Fig. 6 present invention_1-n(WO₄)_1-xCl_2x: the chromaticity diagram of nEu: (a) λ_ex=250nm (b) λ_ex=294nm.

Detailed description of the invention

Following example are intended to illustrate the present invention rather than limitation of the invention further.

Comparative example 1, embodiment 1-5

By Sr_0.95(WO₄)_1-xCl_2x: 0.05Eu stoichiometric proportion weighs strontium carbonate (SrCO₃), ammonium metatungstate (NH₄)₆H₂W₁₂O₄₀·nH₂O (molecular weight: 2956.26), ammonium chloride (NH₄Cl) (analytical pure it is above) and europium oxide (Eu₂O₃) (99.99%), wherein x value is followed successively by 0,0.01,0.02,0.03,0.04 and 0.05, and the sample reference numeral obtaining comparative example 1 is designated as sample N2, N3, N4, N5, the N6 of N1, embodiment 1-5.Analytical balance is used in weighing of material, and its precision is 0.1 milligram. Load weighted raw material is respectively placed in different agate mortars by number be fully ground 1.5h and makes its mix homogeneously, then ground raw material is put into corundum crucible, in the lower 900 DEG C of roasting 3h of high temperature resistance furnace air atmosphere. High temperature resistance furnace temperature program(me) is set to: 200 DEG C/30min to 800 DEG C, then 100 DEG C/30min to 900 DEG C. Sample has sintered rear furnace cooling and has namely obtained material requested to room temperature.

N1-N6 test and the sign of sample

Powder x-ray diffraction analysis is carried out with DMAX-2500 type X-ray diffractometer (XRD) powder body to sintering. Test parameter is: Cu (K α) target, tube voltage 40Kv, tube current 250mA, sweep limits 5-80 °. Scanning step 0.02 °, scanning speed is 10 °/min.

The information analysiss such as the pattern of powder body, particle size, dispersibility carry out on the Quanta200 environmental scanning electron microscope (ESEM) that FEI Co. of the U.S. produces.

Spectrofluorimetry adopts excitation spectrum and the emission spectrum of fluorescent material prepared by Hitachi F-4500 type fluorescence spectrophotometer measurement. Test condition is: xenon lamp lamp source, slit width 10nm, voltage 400V, scanning speed 240nm/min.

Result and discussion

1, structural analysis

Fig. 1 is the Sr of Solid phase synthesis_0.95(WO₄)_1-xCl_2x: the XRD figure of 0.05Eu. Fig. 1 (a) for N3 sample (on) with standard PDF card (under) (card number: PDF#85-0587) compare figure, as can be seen from the figure, the spectral line of N3 sample and card fits like a glove, it does not have any assorted peak phase occur. Fig. 1 (b) is the XRD figure of N1-N6 sample, and the intensity of all spectral lines and peak position and standard spectrum are basically identical, it is seen that Cl^-And Eu²⁺/Eu³⁺Doping to SrWO₄Crystal structure impact is little, and the sample crystal formation of preparation is good, and thing is mutually single. The strongest diffraction maximum of series of samples is all about 27.5, corresponding to SrWO₄(112) crystal face, illustrate synthesis the scheelite-type structure that sample is tetragonal crystal system.

Fig. 2 is N3 sample Sr_0.95(WO₄)_0.98Cl_0.04: the SEM figure of 0.05Eu. Fig. 2 (a) is the design sketch after amplifying 2500 times, and solid phase method sinters the granule of (a) reunion, but size is substantially uniform, produces without obvious second-phase, is consistent with XRD result. The Fig. 2 (b) design sketch for amplifying 10,000 times, with the SrWO obtained by ion implantation such as L.S.Cavalcante₄Crystallite high magnification FESEM figure is basically identical. It can be seen that powder granule spherical in shape, size is approximately 2um, and the powder after reunion is petal-shaped, extends from the inside to the outside.

2, excitation spectrum and emission spectrum

Fig. 3 is the excitation and emission spectra figure of N2 sample. Its monitoring wavelength of the excitation spectrum of Fig. 3 (a) is 397nm, and excitation spectrum is unique wideband spectrum, and its peak value, at about 250nm, is Eu²⁺And Eu³⁺Excitation spectrum; Under the exciting of 250nm ultraviolet, emission spectrum is the broadband emission from 350nm to 600nm, comprises Eu²⁺Characteristic emission and the broadband emission of tungstate radicle, in addition with several obvious Eu³⁺The spectral line of emission, 469nm, 590nm, 616nm emission spectra is corresponding Eu respectively³⁺'s⁵D₂→⁷F₀,⁵D₀→⁷F₁,⁵D₀→⁷F₂Transition, but its emissive porwer is all only small. Fig. 3 (b) excite for 294nm under emission spectrum, mainly by the broadband emission of one section of 350nm to 550nm and 616nm place wire launch constitute. Broadband emission shape very irregular, because this section of transmitting is made up of three parts, wherein peak value corresponds to Eu in the broadband emission of about 410nm²⁺Characteristic emission, peak value is Eu in the transmitting of 469nm³⁺'s⁵D₂→⁷F₀Transition is launched, and this two parts emission spectra is entrained in the broadband emission of whole tungstate radicle.Fig. 3 (b) upper left is the 616nm excitation spectrum monitoring under wavelength, the wire of the broadband excitation of 294nm, 397nm and 469nm place excite and 350nm strong absorption band three part backward is constituted. The broadband emission of 294nm belongs to Eu²⁺/Eu³⁺Ground state is to the absorptive transition of charge transfer state, corresponding to O^2-→Eu²⁺/Eu³⁺And O^2-→W⁶⁺The exciting of charge transfer band. Two lines shape excitation spectrum corresponds to Eu³⁺'s⁷F₀→⁵L₆(397nm) and⁷F₀→⁵D₂(469nm) transition. If system does not introduce Cl-, then the SrWO of Eu3+ doping₄System 350nm does not have excitation band backward, so, this section of excitation band is possibly due to Cl^-After doping, part Eu³⁺Being excited to charge transfer state, electric charge is from Cl^-3p transfer to Eu³⁺4f, Eu³⁺It is reduced to Eu²⁺。Eu²⁺Ground state level be 4f⁷, lowest excited state is likely to by 4f⁷Or 4f⁶5d is formed, and works as 4f⁶Time stronger with 5d electron interaction, energy level severity of mixing up is strengthened, and produces excitation band.

3、Cl^-The concentration impact on material emission performance

Different Cl^-Content, substrate is different with centre of luminescence influence, then excitation spectrum and emission spectrum have very big change. Fig. 4 is different Cl^-The excitation spectrum of content and emission spectrum figure. Fig. 4 (a) is the 397nm excitation spectrum monitoring wavelength, is doped into a small amount of Cl^-After, N2, the excitation spectrum of N3 sample is the broadband excitation spectrum of 250nm, by Eu²⁺And Eu³⁺Excitation spectrum collectively form, Eu²⁺And Eu³⁺Material total amount constant, therefore the excitation spectrum intensity of this section is not with Cl^-The change of content and change. Along with Cl^-The increase of content, there is second segment broadband excitation spectrum in 281nm place, and this section of wideband spectrum is mainly by O^2-→Eu²⁺And O^2-→W⁶⁺Charge transfer band is formed, Cl^-The increase of content exacerbates Eu³⁺Increasing of charge transfer state, Eu²⁺Content increases, therefore this section of exciting line intensity Cl^-The increase of content and become strong. 3rd section of wideband spectrum peak value is positioned at 326nm place, the Eu belonged to²⁺Typical case excites. The emission spectrum Waterfall plot that Fig. 4 (b) is 250nm excitation wavelength, whole emission spectrum is considered as a broadband excitation spectrum, and the emissive porwer of about 397nm is by Eu²⁺D-f transition and Eu³⁺F-f transition joint contribution, so intensity is basically unchanged; The broadband emission of remainder is contributed by tungstate radicle; Although the spectral line of emission relative intensity that N2 and N3 sample is at 616nm place is relatively low but still visible, (N3), Eu as x=0.03³⁺616nm characteristic spectral line disappear, Eu is described³⁺Concentration be not enough to launch the energy that can be sensed by detector.

Fig. 4 (c) monitors the excitation spectrum of wavelength for 616nm, and the excitation spectrum of N2 and N3 sample is mainly by Eu³⁺O^2-→Eu³⁺And O^2-→W⁶⁺Charge transfer band (294nm),⁷F₀→⁵L₆(397nm) and⁷F₀→⁵D₂(469nm) transition is constituted, and Eu during x=0.02 is described³⁺Concentration still significantly high. No longer there is obvious Eu in the excitation spectrum of N4, N5 and N6 sample³⁺Exciting line, Eu is described³⁺Major part is excited to charge transfer state, is reduced to Eu²⁺. Fig. 4 (d) is the emission spectrum Waterfall plot of the series of samples that 294nm wavelength excites, and 294nm is O^2-→Eu²⁺/Eu³⁺And O^2-→W⁶⁺Charge transfer band, Eu under the exciting of 294nm²⁺And Eu³⁺The emission spectrum of self can both be launched. Cl is can clearly be seen that from figure^-The increase of the content impact on system emission spectrum, N2 sample luminescence is tungstate ion and Eu³⁺The coefficient result of emission spectrum; N3 sample occurs in that emission peak near 400nm, and this is Eu²⁺The combined effect of emission spectrum and tungstate ion emission spectrum, Eu³⁺Intensity of emission spectra still very big; N4 sample can be used as the turnover of whole process, Eu³⁺Characteristic peak at 616nm disappears, Eu²⁺Emission peak near 400nm occurs;The emission spectrum of N5 with N6 sample hereafter is similar, it does not have Eu³⁺Characteristic peak, illustrate as x=0.04, Eu³⁺Major part is reduced to Eu²⁺。

Fig. 5 is N5 and N6 sample emission spectrum under 281nm wavelength excites, corresponding to λ in Fig. 4 (a)_em=397nm excites. It can be seen that under 281nm wavelength excites, the emission spectrum of N5 and N6 sample is mainly by Eu²⁺Characteristic spectral line constitute, secondly also have the transmitting of the relatively low tungstate ion of relative intensity, Cl^-System is not had too much influence by concentration.

4、Sr_1-n(WO₄)_1-xCl_2x:nEu²⁺/Eu³⁺Illumination effect

Table 1 is the different Cl utilizing CIE1931 chromaticity coordinates software for calculation to calculate^-Content is Sr under different excitation wavelengths_1-n(WO₄)_1-xCl_2x:nEu²⁺/Eu³⁺The chromaticity coordinates of luminescent material. In table, W1 value is 250nm, W2 value is 294nm. Along with Cl^-Content increases, and the chromaticity coordinates X of the series of samples that 250nm excites, Y value are gradually increased, and colour temperature is gradually reduced, and corresponding dominant wavelength is basically unchanged; 294nm excite under chromaticity coordinates X, Y of sample first increase, from N4 sample, coordinate values reduces suddenly, the numerical value of N5, N6 slowly diminishes below, and then in contrast, N3 reduces colour temperature than N2, N4 increases suddenly, N5, N6 significantly raise below, and dominant wavelength is little in N2, N3 phase change, and the later stage continues to reduce.

Table 1 chromaticity coordinates, colour temperature and corresponding dominant wavelength

CIEchromaticitycoordinates(x,y)atdifferentexcitationwavelength

Fig. 6 is the chromaticity diagram drawn according to chromaticity coordinates. Under the exciting of 250nm ultraviolet, series of samples is luminous close to white portion by blue region; Under 294nm burst of ultraviolel, series of samples is first turned to green area by white portion, then close to blue region. This is primarily due to work as Cl^-When concentration is less, the luminescence of sample is by WO₄ ^2-、Eu²⁺And Eu³⁺Jointly complete, along with Cl^-The increase of concentration, when x >=0.03, the luminescence of sample is mainly WO₄ ^2-And Eu²⁺Tuning result. Comparison sheet 1 is it can be seen that work as Cl^-When concentration is relatively low, the blue light wave that centre wavelength is about 477 can be obtained under the exciting of 250nm ultraviolet, but its colour temperature is high, can be used for the place that cool colour demand is higher, also other fluorescent material that can be relatively low with colour temperature is arranged in pairs or groups, to obtain the chromaticity requirements required for white light LEDs; Under the exciting of 294nm ultraviolet, then can obtain the white light that colour temperature is moderate, illumination effect is good, it is not necessary to allocate with other fluorescent material, this just white light LEDs in illumination, display lamp etc. required for result.

4 conclusions

High temperature solid-state method is adopted to synthesize Sr (WO₄)_1-xCl_2x:Eu²⁺/Eu³⁺Luminescent material. XRD test shows that this fluorescent material is still single-phase crystal when x=0.05, and FESEM shows that its exterior appearance is uniform spheroidal particle, and diameter is about 2um. Under the burst of ultraviolel of 250nm, fluorescent material is with Cl^-The increase of concentration is close to white light field by blue light, and colour temperature is high; Under the burst of ultraviolel of 294nm, fluorescent material is with Cl^-Increasing of concentration is close to blue region by the white light that chromaticity matter is good. Chromaticity coordinates and chromaticity diagram show, when x is between 0.01 and 0.02, the fluorescent material of body series has blue light and the white-light emitting effect of the best, when x >=0.03, and Eu³⁺Ion concentration is not enough to show its emission spectrum. System has three centres of luminescence, is WO42-, Eu respectively²⁺And Eu³⁺, there is outstanding luminescent quality, it is possible to as the blue emitting phosphor of specific use, it is also possible to separately as the potential succedaneum of white light LEDs.

Claims

1. one kind based on blue light under burst of ultraviolel-white light conversion phosphor, it is characterised in that chemical formula is Sr_1-n(WO₄)_1-xCl_2x: nEu fluorescent material is single-phase luminescent material, has WO₄ ^2-、Eu²⁺And Eu³⁺Three centres of luminescence, n, X are molal quantity, 0 < X < 0.03,0.03≤n≤0.15.

2. according to claim 1 based on blue light under burst of ultraviolel-white light conversion phosphor, it is characterised in that 0.01≤X < 0.03.

3. according to claim 2 based on blue light under burst of ultraviolel-white light conversion phosphor, it is characterised in that 0.01≤X≤0.02.

4. according to claim 1 based on blue light under burst of ultraviolel-white light conversion phosphor, it is characterised in that 0.05≤n≤0.1.

5. according to claim 1 or 2 or 3 or 4 based on blue light under burst of ultraviolel-white light conversion phosphor, it is characterised in that under the ultraviolet excitation of 240～260nm, fluorescent material blue light-emitting; Under the ultraviolet excitation of 266～300nm, fluorescent material emits white light.

6. according to claim 5 based on blue light under burst of ultraviolel-white light conversion phosphor, it is characterised in that under the ultraviolet excitation of 250nm, fluorescent material blue light-emitting; Under the ultraviolet excitation of 294, fluorescent material emits white light.

7. the preparation method based on white light-white light conversion phosphor blue under burst of ultraviolel described in any one of claim 1-6, described fluorescent material is to be synthesized by high temperature solid state reaction in air atmosphere by the raw material preparing fluorescent material; Described high temperature is 800 DEG C～950 DEG C.

8. the preparation method based on white light-white light conversion phosphor blue under burst of ultraviolel according to claim 7, described phosphor raw material is: strontium carbonate, ammonium metatungstate, ammonium chloride and europium oxide, by generating Sr1-n (WO₄)_1-xCl_2x: the stoichiometric proportion preparation needed for nEu is ground, and high temperature solid state reaction synthesizes.

9. according to claim 7 based on white light-white light conversion fluorescence powder, preparation method thereof blue under burst of ultraviolel, it is characterised in that the high temperature solid state reaction time is 1～4 hour.