CN1363643A

CN1363643A - Process for preparing nano yttrium aluminate as fluorescent powder

Info

Publication number: CN1363643A
Application number: CN 01138218
Authority: CN
Inventors: 袁曦明
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-11-26
Filing date: 2001-11-26
Publication date: 2002-08-14
Anticipated expiration: 2021-11-26
Also published as: CN1142238C

Abstract

A nano fluorescent yttrium aluminate powder is prepared by the combination of sol-gel method with microwave method. Its advantages include low temp for preparing it, short preparing temp. and high uniformity, purify and luminous nature of product. It can be used for plasma display panel, field-luminous display screen, etc.

Description

The method for preparing nano yttrium aluminate as fluorescent powder

Technical field

The present invention relates to the nano rare earth yttrium aluminate as fluorescent powder, particularly prepare the method for nano yttrium aluminate as fluorescent powder.

Background technology

Because the relative luminous intensity of nano rare earth fluorescent material has been compared with micron fluorescent material and has been significantly improved, and the frequency displacement phenomenon can appear in emission wavelength, therefore, the nano rare earth luminescent material becomes a new and developing branch of luminescent material research field, and nano rare earth high-efficiency fluorescence powder has important application prospects on plasma display panel (PDP) (PDP), el display panel (EL).At present, preparation fluorescent RE powder method is a lot, as high temperature solid-state method etc., the fluorescent material of these method preparations all is micron order, and the sintering temperature that this producing and manufacturing technique requires is than higher, generally more than 1200 ℃, production cycle is longer, and the cost height is unfavorable for scale operation.

Summary of the invention

Technical problem to be solved by this invention is: the method for preparing nano yttrium aluminate as fluorescent powder, the sintering temperature that this method requires is lower than the temperature of high temperature solid-state method preparation micron fluorescent material, production cycle is shorter, and the product that makes chemistry good uniformity, purity height, luminescent properties significantly improve.

The present invention solves the problems of the technologies described above the technical scheme that is adopted: its method steps is:

(1), rare earth oxide is obtained the mixed polymer colloidal sol of Citrate trianion with sol-gel method;

(2), step (1) gained colloidal sol is put in the microwave oven heating and obtained gelinite;

(3), gelinite is obtained xerogel by drying;

(4), xerogel is heat-treated under differing temps, and carry out the product particle surface and modify, just obtain nano yttrium aluminate as fluorescent powder (Y ₄Al ₂O ₉: Eu ³⁺).

The present invention combines sol-gel method and forms new prepared route with microwave method, preparation nano rare earth yttrium aluminate as fluorescent powder (Y ₄Al ₂O ₉: Eu ³⁺).In preparation process, impel doping with rare-earth ions evenly and promptly to spread by microwave heating and form the soluble chelating thing with citric acid, thereby, by microwave action colloidal sol is transformed also to gel again and shortened the production cycle greatly for the preparation of twinkler provides the presoma of forming and being evenly distributed.After 800 ℃～1200 ℃ calcinations, its product particle surface is modified, just can obtain nano rare earth yttrium aluminate as fluorescent powder (Y ₄Al ₂O ₉: Eu ³⁺).

The sintering temperature that the inventive method requires obviously reduces than the temperature of high temperature solid-state method preparation micron fluorescent material, generally at 800 ℃～1200 ℃; Shorten the production cycle; The product chemical uniformity, purity, the luminescent properties that make all significantly improve; Product cost is low, is beneficial to scale operation.This novel red nano-phosphor can be applicable to PDP, EL, luminescent lamp, onboard instruments, mobile video telephone, game machine and ceramic scintillator etc.

Description of drawings

Fig. 1 is an embodiment of the invention schema

Fig. 2 is the powder crystal diffractogram of the inventive method nano yttrium aluminate as fluorescent powder that calcination obtains under differing temps

Fig. 3 is the transmission electron microscope high resolution pattern picture of the inventive method gained nano yttrium aluminate as fluorescent powder

Fig. 4 is the inventive method gained nano yttrium aluminate as fluorescent powder transmission electron microscope high resolving electron diffraction picture

Fig. 5 is the excitation spectrum of the inventive method gained nano yttrium aluminate as fluorescent powder

Fig. 6 is the emmission spectrum of the inventive method calcination gained nano yttrium aluminate as fluorescent powder under non-reduced atmosphere

Fig. 7 is the emmission spectrum of the inventive method calcination gained nano yttrium aluminate as fluorescent powder under reducing atmosphere

Specific embodiments

As shown in Figure 1, production craft step of the present invention is: take by weighing Y by certain stoichiometric ratio ₂O ₃(99.99%) is 4.5200 grams, Al (NO ₃) ₃9H ₂O (AR) is 7.5000 grams, and citric acid (AR) is 48.2600 grams, HNO ₃(AR) be 1.8900 grams, Eu ₂O ₃(99.99%) is 0.3520 gram.Control weighing citric acid amount of substance is between 1.5～6.5 times of total amount of metal ion species such as rare earth.With Eu ₂O ₃, Y ₂O ₃Dissolve in 0.1-1N HNO respectively ₃Can obtain nitrate solution, will be by the Al (NO of stoichiometric ratio weighing ₃) ₃9H ₂O and citric acid dissolve, and mix the mixed polymer solution that can obtain Citrate trianion with the nitrate solution that contains rare earth that obtains previously.In said process, note controlling amount of water.How many general mole ratio R=[H that use of amount of water ₂O]: [M (OR)] expression.Amount of water and prepared dissolved adhesiveness and gelation time have substantial connection, and R need be controlled between 2～8.The excessive then viscosity degradation of R, gelation time prolongs, because too much water has watered down the concentration of inner complex.The too small dissolving that then is unfavorable for nitrate and citric acid of R, thus can not form uniform solution and precipitating metal nitrate.Simultaneously, too much water also can make prolong time of drying.PH is also very crucial in preparation process, and PH should be controlled at 2～8 scopes.PH value is unfavorable for the stable of inner complex too greatly, and crystallization and precipitation can occur.Just obtain colloidal sol behind the regulation and control mixing solutions pH value, insert that heating obtains gelinite in the microwave oven.Gelinite inserted drying obtains xerogel in the microwave oven.Xerogel is heat-treated under 800～1200 ℃.Then the product particle surface is modified, promptly used the immersion of 0.01～0.5M gelatin solution, stirring, separation, drying, just obtain nano rare earth fluorescent material Y ₄Al ₂O ₉: Eu ³⁺

Y ₂O ₃-Al ₂O ₃There are three different thing phases: YA1O in two component system ₃, Y ₃Al ₅O ₁₂And Y ₄Al ₂O ₉, this was studied in existing relevant document, three kinds of things of yttrium aluminate mutually in, preceding two kinds of matrix as fluorescent material were widely studied, and Y ₄Al ₂O ₉As luminous host but be studied few.In the research, I find just can obtain fluorescent material Y with sol-gel processing at 800 ℃ ₄Al ₂O ₉The thing phase, 900 ℃ of following calcinations can obtain its pure thing phase, and the gained powder is observed down at transmission electron microscope (TEM), and the granular size of fluorescent material is at nano level (as Fig. 3).

Determining of calcination temperature: xerogel is put into the calcination under different temperature of high temperature cabinet-type electric furnace, the sample that obtains is carried out X ray powder crystal diffraction (XRD) analysis, found that in the time of 800 ℃, to begin to occur nanometer crystalline phase Y ₄Al ₂O ₉Product has been Y when (YAO), reaching 900 ℃ ₄Al ₂O ₉Pure phase, then respectively 1000 ℃, 1200 ℃ following calcinations, the product that obtains still is Y ₄Al ₂O ₉, the XRD of series of samples such as Fig. 2.The pattern of product and particle diameter are observed with transmission electron microscope (TEM), Figure 3 shows that the pattern picture (BF) of the nano-phosphor that obtains after 900 ℃ of following calcinations, Figure 4 shows that electron diffraction picture (ED).As can be seen from Figure 3 between 20nm～50nm, the statistical study median size is 30nm to grain diameter basically.By transmission electron microscope observation, most of particulates of the nano-phosphor of synthetic preparation are spherical or subsphaeroidal.Discover the raising along with calcination temperature, it is big that the particle diameter of YAO fluorescent powder grain can become gradually.When sintering temperature reaches 1200 ℃, the particle diameter of YAO is basically more than 1um.In addition, compare with a high temperature solid-state method preparation micron fluorescent material temperature with temperature shown in the phasor of Fig. 2 and relevant bibliographical information, the method that adopts sol-gel method to combine with microwave method prepares nanocrystalline Y ₄Al ₂O ₉The thing phase, it burns temperature can be reduced to 800 ℃, and the production cycle has also shortened greatly.

The present invention adopts direct calcination xerogel and calcination under activity charcoal powder reductive atmosphere respectively, finds that the nanometer crystalline phase that obtains is same thing phase YAO.

The present invention studies exciting with emmission spectrum of gained nano-phosphor.Be illustrated in figure 5 as the excitation spectrum of gained under emmission spectrum 598nm monitoring, spectrogram 1 is the excitation spectrum of the sample for preparing under the non-reduced atmosphere, and peak value is respectively 394.3nm, 438.5nm, 470.8nm; Spectrogram 2 is the excitation spectrum of the sample of preparation under the reducing atmosphere, and the peak value of appearance is respectively 340.1nm, 395.7nm, 471.2nm.Both difference are 340.1nm and 438.5nm two excitation peaks, and the major cause that these different peaks occur is Eu ³⁺The fine difference of residing crystallographic site causes in the YAO nanocrystalline structure.Above-mentioned excitation peak is because Eu ³⁺The transition of f-f absorb and to cause.Y ₄Al ₂O ₉Crystalline structure is an oblique system, and spacer is P2 ₁/ C, point group are C _2hWhen doping Eu ion to Y ₄Al ₂O ₉In the time of in the crystal, because Eu ionic radius and Y ³⁺Radius (R _Y ³⁺=0.088nm) more approaching, so Eu generally occupies Y in lattice ³⁺The position, and Eu generally exists with two kinds of ionic speciess: Eu ³⁺(R _Eu ³⁺=0.095nm) and Eu ²⁺(R _Eu ²⁺=0.109nm), from valence state and ionic radius consider the Eu ion should with the trivalent form be present in nanocrystalline.In conjunction with emmission spectrum, the emission peak in the spectrum all is Eu ³⁺ ⁵D ₀→ ⁷F _JThe feature emission that produces of transition, even and the reducing atmosphere fluorescent material of preparation down, Eu does not appear in its emmission spectrum yet ²⁺The emission of ionic feature, Eu is at nanocrystalline Y in this explanation ₄Al ₂O ₉In be form Eu with trivalent ion ³⁺Exist, the reason that causes this result is just due to the acting in conjunction of ionic radius and charge balance.Analyze emmission spectrum, find in the experiment different emission peaks can occur when with different optical excitation, the emission spectrum that is occurred after the optical excitation of wavelength X=400nm is unimodal λ=597.8nm, is orange light emission (seeing shown in Figure 6).Orange light emission about λ=590nm has not only appearred in the emission peak that is produced behind the ultraviolet excitation of wavelength X=254nm, and the red emission (seeing shown in Figure 7) of λ=610nm occurred.According to Eu in the crystal ³⁺The general rule of transition of electron is worked as Eu ³⁺When being in the case that the strict centre of inversion is arranged, will with ⁵D ₀→ ⁷F ₁It is main that orange light (about 590nm) is launched in the magnetic dipole transition that allows; Work as Eu ³⁺When being in the case that departs from the centre of inversion, because at 4f ⁶Sneaked into the ununiformity of 5d and the 5g configuration and the crystal field of opposite parity in the configuration, the parity selection rule in the crystal is relaxed, the f-f forbidden transition is partly lifted a ban, and will occur ⁵D ₀→ ⁷F ₂Deng electric dipole transition; Work as Eu ³⁺When being in the case of no inversion center of symmetry, often with ⁵D ₀→ ⁷F ₂Electric dipole transition red-emitting (about 610nm) is emitted as the master.The brilliant Y of combining nano ₄Al ₂O ₉Constructional feature, its point group are C _2b, because Eu ³⁺At nanocrystalline Y ₄Al ₂O ₉In occupy Y ³⁺The position, Eu thus ³⁺Should be in the case that the strict centre of inversion is arranged, its emission should be ⁵D ₀→ ⁷F ₁The magnetic dipole transition orange light (about 590nm) that allows is emitted as the master.Orange light and red emission in preparing the spectrogram of product, have occurred, and the latter's intensity is greater than the former, this explanation part Eu in nanocrystalline ³⁺Be in the case that departs from the centre of inversion, so occurred ⁵D ₀→ ⁷F ₂Electric dipole transition ruddiness (about 610nm) emission.

Claims

1, a kind of method for preparing nano yttrium aluminate as fluorescent powder, it is characterized in that: its method steps is:

(1), with rare earth oxide Eu ₂O ₃Obtain the mixed polymer colloidal sol of Citrate trianion with sol-gel method;

(3), gelinite is obtained xerogel by drying;

(4), xerogel is heat-treated under differing temps, and carry out the product particle surface and modify, just obtain nano yttrium aluminate as fluorescent powder.

2, the method for claim 1 is characterized in that: sol-gel method is: with rare earth oxide Eu ₂O ₃Dissolve in 0.1-1N HNO ₃In, obtain nitrate solution, then with the mixed mixed solution that gets of other nitrate solution; Add citric acid in above-mentioned solution, obtain the mixed polymer solution of Citrate trianion, regulation and control mixing solutions PH numerical value is 2-8, makes colloidal sol.

3, method as claimed in claim 2 is characterized in that: the steps include: that used citric acid adds the overall control of amount of substance and metal ion such as rare earth doped between 1.5 times～6.5 times.

4, method as claimed in claim 1 or 2 is characterized in that: add entry in the sol-gel method process, what of amount of water are used mole ratio R=[H ₂O]: [M (OR)] expression, R is controlled between 2～9.

5, the method for claim 1 is characterized in that: xerogel is heat-treated under 800 ℃～1200 ℃.

6, the method for claim 1 is characterized in that: product particle surface modification process is: with the immersion of 0.01～0.5M gelatin solution, stirring, separation, drying.