CN101402857A - Red luminous material for LED and producing process thereof - Google Patents

Abstract

The invention discloses a red luminescent material for LED and a preparation method thereof. The general chemical formula is Ca _1-x-y Sr _x Mg _y Al _12-z O ₁₉ :Mn ⁴⁺ _z , where 0≤x<0.5, 0≤y<1, z=0.01-10%, and the preparation method is as follows: Dissolve soluble metal acetate, nitrate and other raw materials in water, mix evenly according to the metering ratio, and add one or more fuels: urea, citric acid, boric acid and glycine respectively to form a transparent viscous solution, heat Concentrate to dryness to obtain a yellow or brown powder precursor. The precursor is fired in the air at 500-900°C for 5-12 hours, cooled, ground, then sintered in the air at 1100-1300°C for 5-24 hours, and naturally cooled to room temperature to obtain the product. The material is used for white light LED, and the preparation method is 200-400°C lower than the traditional synthesis method.

Description

A kind of red luminescent material for LED and preparation method thereof

technical field

The invention relates to a luminescent material, in particular to a red luminescent material which can be used for LED and a preparation method thereof.

Background technique

White LEDs packaged by yellow phosphor YAG:Ce and blue LEDs are the earliest white LEDs invented, and they are also the mainstream products in the current white LEDs market. However, the color rendering index of such white LEDs is low and cannot meet large-scale lighting needs, because the white light has only yellow and blue components, and less red components. In order to improve the color rendering index of this type of white LEDs, a lot of work has focused on substituting Gd ³⁺ for YAG:Ce to partially replace Y ³⁺ in YAG:Ce to redshift the emission spectrum to increase its emission intensity in the red region, but this The red shift of the emission band needs to be sacrificed at the expense of luminous intensity and luminous efficiency (J.Electrochem.Soc.2007, 154, J326; Mater.Res.Bull.2008, 43, 1657; , 9200). In addition, co-doping Sm ³⁺ , Pr ³⁺ , and Eu ³⁺ in YAG:Ce can increase red light emission, but compared with Ce ³⁺ , when excited by blue light, the luminous efficiency of these rare earth ions in YAG matrix is not as good. High (J. Phys. Chem. Solid. 2004, 65, 845). Therefore, mixing a high-efficiency phosphor that has strong absorption in the blue region and emits red light in the phosphor YAG:Ce will be a more effective method to improve the color rendering index of current white LEDs.

Traditional Eu ³⁺ activated red phosphors are widely used in various lighting and displays due to their high efficiency and high color purity, but the luminescence of Eu ³⁺ ions is caused by its ff transition, so the excitation peak is near Both the ultraviolet and blue regions have narrow emission peaks, which limit their application in current white LEDs (Phosphor Handbook, CRC Press, 2006; Practical Applications of Phosphors, CRC Press, 2006). Commercial lamp powder 3.5MgO.0.5MgF ₂ .GeO ₂ :Mn ⁴⁺ has been invented for more than 40 years (J.Chem.Phys.1960, 33, 783), and it is still in use, but because the raw materials used are too expensive High, it can only be used in special fluorescent lamps to improve the color rendering index of fluorescent lamps. Compared with rare earth luminescent materials, the luminescent materials activated by Mn ions have low raw material prices. Compared with other rare earth ions such as Ce ³⁺ , Eu ²⁺ and transition metal ions such as Mn ²⁺ that emit light caused by fd or dd catapults, this The Mn ⁴⁺ red luminescent material in the invention does not need a reducing atmosphere, but is synthesized in the air, thus greatly reducing the requirements for production equipment and production costs. In recent years, the luminescence of CaAl ₁₂ O ₁₉ :Mn ⁴⁺ has been studied and reported (J.Lumin.2005, 114, 207; Opt.Lett.2008, 33, 1-3), and found that with some Mg ions Replacing Ca ions therein can effectively improve its luminous efficiency. The high-temperature solid-phase method synthesizes the material at a temperature as high as 1600 °C.

Contents of the invention

The purpose of the present invention is to overcome the disadvantages of the prior art, and provide a red luminescent material for LED that does not contain rare earths, does not contain precious raw materials, has low sintering temperature and low preparation cost and its preparation method.

The purpose of the present invention is achieved through the following technical solutions:

A red luminescent material for LED, its chemical composition formula is: Ca _1-xy Sr _x Mg _y Al _12-z O ₁₉ :Mn ⁴⁺ _z , wherein 0≤x<0.5, 0≤y<1, z=0.01 ~0.1, the material can be excited by near ultraviolet and blue light, and emit bright deep red fluorescence. The excitation spectrum of this material is composed of three broad bands, which have strong absorption in the near ultraviolet and blue light regions. The highest positions of the excitation spectrum are located at 340nm, 390nm and 466nm respectively, and the emission peak is a wide emission band between 620nm and 700nm. Under ultraviolet light, its brightness is close to that of commercial lamp powder 3.5MgO.0.5MgF ₂ .GeO ₂ :Mn ⁴⁺ . At the same time, this material can be excited by purple and blue LEDs currently on the market to emit deep red fluorescence, so it is expected to be applied In the current market, purple LEDs can be combined with other green and blue phosphors to form white LEDs. They can also be used in white LEDs packaged with blue LEDs and YAG:Ce to improve the current situation of low color rendering index. , realizing the wide application of existing white light LEDs.

The preparation method of the red luminescent material for LEDs: dissolving the raw materials calcium acetate, aluminum nitrate, strontium nitrate, magnesium nitrate and manganese acetate in water, according to the chemical composition formula Ca _1-xy Sr _x Mg _y Al _12-z O ₁₉ : Mn ⁴⁺ _z , where 0≤x<0.5, 0≤y≤1, z=0.01～0.1 metering ratio Mix the above solutions evenly, add fuel, form a transparent viscous solution after stirring, put it on the electric furnace, Heat and condense to burn to obtain yellow or brown precursor powder; pre-burn the precursor in the air at 500-900°C for 5-12 hours, grind it, then sinter it in the air at 1100-1300°C for 5-24 hours, and cool it naturally After reaching room temperature, the red luminescent material for LED can be obtained; the fuel used is one or two of urea, citric acid, boric acid and glycine, and the dosage is 2 to 4 times the total molar weight of metal ions.

In order to further realize the purpose of the present invention, the said pre-calcination temperature is preferably 600-800°C.

The said pre-burning time is preferably 8-10 hours.

The sintering temperature is preferably 1200-1300°C.

The sintering time is preferably 10-18 hours.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

The material of the invention has strong absorption bands in the near ultraviolet and blue light regions, and emits bright deep red light. The operation steps are simple. Since the material in the present invention does not contain rare earths or other valuable raw materials, and the synthesis of the material by the combustion method can make the crystallization temperature 300-500°C lower than that of the traditional high-temperature solid-phase method, the cost of raw materials required for the synthesis of the material is low, The preparation process has low requirements on equipment, which is conducive to improving its market competitiveness and realizing its large-scale application in the field of lighting and display.

Description of drawings

Fig. 1 Excitation spectrum and emission spectrum of Ca _0.4 Mg _0.6 Al ₁₂ O ₁₉ :Mn ⁴⁺ prepared in Example 5 of the present invention (left: λem=655nm, right: λex=466nm).

Detailed ways:

The present invention will be further described below in conjunction with the drawings and examples, and the protection scope of the present invention is not limited to the range expressed in the examples.

Accurately weigh the solid raw materials calcium acetate Ca(Ac) ₂ .H ₂ O, aluminum nitrate Al(NO ₃ ) ₃ .9H ₂ O, strontium nitrate Sr(NO ₃ ) ₃ , magnesium nitrate Mg(NO ₃ ) ₂ .6H ₂ O. Dissolve in water respectively, and prepare corresponding solutions with a concentration of 0.5mol/L. Dissolve manganese acetate Mn(Ac) ₂ .4H ₂ O in water to prepare a manganese acetate solution with a concentration of 0.00005mol/L.

Example 1

_{Accurately measure the above} ^Ca ( _Ac ) ₂ , Al(NO ₃ ) ₃ , Mn(Ac) ₂ solutions, after uniform mixing, add urea whose molar mass is 3 times the total molar amount of metal ions, stir to dissolve, form a transparent viscous solution, and place it on an electric furnace , heating and concentrating until burning to obtain a yellow precursor powder, pre-calcining the precursor in air at 500°C for 5 hours, grinding it, and sintering in air at 1300°C for 5 hours, and cooling naturally to room temperature to obtain the product, the product Under the irradiation of ultraviolet lamp, ultraviolet LED or blue LED, it emits deep red fluorescence.

Example 2

_{Accurately measure} ^the _{above Ca} ( _Ac ) ₂ , Sr(NO ₃ ) ₃ , Al(NO ₃ ) ₃ , Mn(Ac) ₂ solutions, after mixing evenly, add citric acid whose molar mass is 3 times the total molar amount of metal ions, stir to dissolve and form a transparent The viscous solution is placed on an electric furnace, heated and concentrated until it burns to obtain a brown precursor powder, which is pre-fired at 600°C in air for 8 hours, then ground, then sintered in 1100°C in air for 24 hours, and cooled naturally to The product can be obtained at room temperature, and the product emits deep red fluorescence under the irradiation of ultraviolet lamp, ultraviolet LED or blue light LED.

Example 3

_Accurately ^measure _{the above Ca} ( _Ac ) ₂ , Mg(NO ₃ ) ₃ , Al(NO ₃ ) ₃ , Mn(Ac) ₂ solutions, after uniform mixing, add citric acid and urea whose molar weight is 1.5 times the total molar amount of metal ions, stir to dissolve , to form a transparent viscous solution, place it on an electric furnace, heat and concentrate until it burns, and obtain a brown precursor powder, pre-burn the precursor in air at 500°C for 5 hours, grind it, and sinter it in air at 1100°C for 18 hours. Cool naturally to room temperature to get the product, which emits dark red fluorescence under the irradiation of ultraviolet lamps, ultraviolet LEDs or blue LEDs.

Example 4

_{Accurately measure} ^the _{above Ca} ( _Ac ) ₂ , Sr(NO ₃ ) ₃ , Mg(NO ₃ ) ₃ , Al(NO ₃ ) ₃ , Mn(Ac) ₂ solutions, after uniform mixing, add citric acid whose molar weight is 1.5 times the total molar amount of metal ions and glycine, stirred to dissolve to form a transparent viscous solution, placed on an electric furnace, heated and concentrated to burn to obtain a brown precursor powder, pre-burned the precursor in air at 900°C for 5 hours, then ground it, and then heated it at 1200 Sinter in air at ℃ for 10 hours, then cool naturally to room temperature to get the product, which emits deep red fluorescence under the irradiation of ultraviolet lamp, ultraviolet LED or blue light LED.

Example 5

_{Accurately measure} ^the _{above Ca} ( _Ac ) ₂ , Mg(NO ₃ ) ₃ , Al(NO ₃ ) ₃ , Mn(Ac) ₂ solutions, after uniform mixing, add citric acid and boric acid whose molar weight is 1.5 times the total molar amount of metal ions, stir to dissolve , to form a transparent viscous solution, put it on an electric furnace, heat and concentrate until it burns, and obtain a brown precursor powder. Pre-burn the precursor in air at 800°C for 10 hours, grind it, and then sinter it in air at 1300°C for 24 hours. Cool naturally to room temperature to get the product, which emits dark red fluorescence under the irradiation of ultraviolet lamps, ultraviolet LEDs or blue LEDs. The product synthesized in this example has the best luminescence performance in the present invention, and its excitation spectrum and emission spectrum are shown in Figure 1. The excitation spectrum of this material is composed of three broad bands, corresponding to the excitation peaks at 340nm, 390nm and 466nm respectively. The emission wavelengths of ultraviolet lamps, ultraviolet LEDs and blue LEDs are broad emission bands between 620 and 700 nm, showing deep red fluorescence. In the present invention, the fluorescence spectra of other embodiments are basically similar to those in FIG. 1 , and will not be described one by one.

Example 6

_{Accurately measure the above} ^Ca ( _Ac ) ₂ , Mg(NO ₃ ) ₃ , Al(NO ₃ ) ₃ , Mn(Ac) ₂ solutions, after mixing evenly, add urea and boric acid in a molar amount equal to 1.5 times the total molar amount of metal ions, stir to dissolve, and form The transparent viscous solution is placed on an electric furnace, heated and concentrated until it burns to obtain a brown precursor powder, which is pre-fired in the air at 900°C for 12 hours, then ground, then sintered in the air at 1200°C for 18 hours, and cooled naturally To room temperature, the product can be obtained. Under the irradiation of ultraviolet lamp, ultraviolet LED or blue LED, the product emits deep red fluorescence.

Example 7

_{Accurately measure} ^the _{above Ca} ( _Ac ) ₂ , Mg(NO ₃ ) ₃ , Al(NO ₃ ) ₃ , Mn(Ac) ₂ solutions, after mixing evenly, add glycine whose molar mass is 3 times the total molar amount of metal ions, stir to dissolve, and form a transparent The viscous solution is placed on an electric furnace, heated and concentrated until it burns to obtain a brown precursor powder, which is pre-fired at 800°C for 12 hours in the air, then ground, then sintered in the air at 1300°C for 24 hours, and cooled naturally to The product can be obtained at room temperature, and the product emits deep red fluorescence under the irradiation of ultraviolet lamp, ultraviolet LED or blue light LED.

Claims (6)

1, a kind of LED red illuminating material is characterized in that: this red illuminating material chemical constitution formula is: Ca _1-x-ySr _xMg _yAl _12-zO ₁₉: Mn ⁴⁺ _z, 0≤x＜0.5,0≤y＜1 wherein, z=0.01～0.1, this material can be by near ultraviolet, blue-light excited, and launches bright scarlet fluorescence.

2, the described LED of a kind of claim 1 preparation method of red illuminating material is characterized in that: raw material calcium acetate, aluminum nitrate, strontium nitrate, magnesium nitrate and manganese acetate is water-soluble, press chemical constitution formula Ca _1-x-ySr _xMg _yAl _12-zO ₁₉: Mn ⁴⁺ _z, 0≤x＜0.5,0≤y＜1 wherein, the metering of z=0.01～0.1 is than with above solution uniform mixing, and adds fuel, stirs the back and forms transparent viscous solution, places on the electric furnace, and heating is concentrated into burning, obtains yellow or brown precursor powder; Precursor pre-burning in 500～900 ℃ of air was ground after 5～12 hours, and sintering 5～24 hours in 1100～1300 ℃ of air naturally cools to room temperature again, get final product the LED red illuminating material; Fuel used is in urea, citric acid, boric acid and the glycine one or both, and consumption is 2～4 times of metal ion integral molar quantity.

3, the LED according to claim 2 preparation method of red illuminating material, it is characterized in that: described calcined temperature is 600～800 ℃.

4, the LED according to claim 2 preparation method of red illuminating material, it is characterized in that: the described pre-burning time is 8～10 hours.

5, the LED according to claim 2 preparation method of red illuminating material, it is characterized in that: described sintering temperature is 1200～1300 ℃.

6, the LED according to claim 2 preparation method of red illuminating material, it is characterized in that: described sintering time is 10～18 hours.

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