CN112608742B - Europium-activated beta-Al 2O3 defect structure blue fluorescent powder and preparation method thereof - Google Patents
Europium-activated beta-Al 2O3 defect structure blue fluorescent powder and preparation method thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of luminescent materials, and particularly relates to europium-activated beta-Al 2 O 3 A defect structure blue fluorescent powder and a preparation method thereof. The chemical structural formula of the blue fluorescent powder is K 0.8‑2x‑2y Ba 0.1+x Eu y Al 11 O 17 Wherein x is more than or equal to 0 and less than or equal to 0.3; y is more than or equal to 0.025 and less than or equal to 0.175. Grinding the raw materials, mixing uniformly, sintering in stages under the condition of introducing reducing atmosphere, cooling to room temperature, and grinding into powder to obtain the blue fluorescent powder. The blue fluorescent powder has a wide excitation band, can be effectively excited by ultraviolet light and near ultraviolet light, has high quantum efficiency (the internal quantum efficiency is more than 90 percent), has better thermal stability than the prior blue commercial fluorescent powder, and has basically unchanged emission intensity along with the temperature rise from room temperature to 200 ℃.
Description
Technical Field
The invention belongs to the technical field of luminescent materials, and particularly relates to europium-activated beta-Al 2 O 3 A defect structure blue fluorescent powder and a preparation method thereof.
Background
White light emitting diodes (abbreviated as WLEDs) have been generally accepted as a new generation of illumination light source, and fluorescence conversion type white light LEDs (abbreviated as pc-WLEDs) dominate the field of general illumination. The fluorescent powder is an important component of pc-WLEDs, and determines the characteristics of light-emitting efficiency, color rendering index, service life and the like of LED equipment.
In the case of pc-WLEDs, the production process has been commercialized as follows: a typical yellow phosphor (YAG: Ce) 3+ ) Coating on an InGaN blue chip. A part of blue light emitted by the chip is used for exciting the fluorescent powder to generate yellow light, and the other part of blue light is combined with the generated yellow light to obtain white light. The method has simple manufacturing process and high luminous efficiency, but the obtained white light has low color rendering index (less than 80) due to lack of green and red spectrum components, and cannot meet the requirement of a general illumination light source on color rendering property. At present, due to the advantages of high color rendering index (more than 85), good spectral stability and the like, a method for obtaining white light by covering red, green and blue fluorescent powder with a near ultraviolet (n-UV, 360-410nm) chip attracts people's extensive attention. Wherein, the currently commonly used commercial blue fluorescent powder is mainly BaMgAl 10 O 17 :Eu 2+ ， (Ca,Sr,Ba) 10 (PO 4 ) 6 Cl 2 :Eu 2+ ，Ba 3 MgSi 2 O 8 :Eu 2+ . The best comprehensive effect on the BaMgAl 10 O 17 :Eu 2+ In addition, the quantum yield can reach more than 90%, the luminous intensity can be kept about 91% at room temperature at 200 ℃, and how to obtain the blue fluorescent powder with better comprehensive performance is still significant.
Based on this, research on blue fluorescent powder with near ultraviolet excitation, high quantum yield and good thermal stability is one of the key points for obtaining high color rendering WLEDs.
Disclosure of Invention
Aiming at the requirement of further improving the performance of commercial blue fluorescent powder, the invention provides the near ultraviolet excited europium-activated beta-Al with high quantum yield and good thermal stability 2 O 3 Structural blue fluorescent powder and a preparation method thereof.
In order to achieve the above object, the present invention provides, in one aspect, a europium-activated β -Al 2 O 3 The blue fluorescent powder with a defect structure has a chemical structural formula of K 0.8-2x-2y Ba 0.1+x Eu y Al 11 O 17 Wherein x is more than or equal to 0 and less than or equal to 0.3; y is more than or equal to 0.025 and less than or equal to 0.175.
In another aspect of the present invention, there is provided the above europium-activated beta-Al 2 O 3 A method for preparing structural blue fluorescent powder. The method comprises the following steps:
step 1: according to the chemical formula K 0.8-2x-2y Ba 0.1+x Eu y Al 11 O 17 Weighing K, Ba-containing carbonate or nitrate and Al-Eu-containing oxide according to the stoichiometric ratio of the chemical compositions; weighing a fluxing agent;
step 2: grinding the raw materials in the step 1, and uniformly mixing to obtain a mixture;
and step 3: carrying out sectional sintering on the mixture obtained in the step 2 under the condition of introducing a reducing atmosphere, and then cooling to room temperature to obtain a sintered material;
and 4, step 4: and (4) grinding the sinter obtained in the step (3) into powder, and sieving the powder with a 300-600-mesh sieve to obtain the blue fluorescent powder.
Further, in the step 3, the reducing atmosphere is composed of 5-10% of H in percentage by volume 2 And 95 to 90% of N 2 And (4) forming.
Further, the step 3 of segmented sintering comprises: firstly, raising the temperature to 800-900 ℃ at the temperature raising rate of 5 ℃/min, and preserving the temperature for 1-2h to promote the decomposition of carbonate or nitrate; then the temperature is raised to 1400 ℃ and 1600 ℃ at the temperature raising rate of 5 ℃/min, and the temperature is preserved for 4-8 hours to ensure the synthesis of the product.
Further, in the step 1, the fluxing agent is AlF 3 、BaF 2 、H 3 BO 3 、CaF 2 One or more of the above; the adding amount of the fluxing agent is 3-5% of the total mass of the raw materials.
The principle of the preparation method of the invention is as follows: the reactants which are thoroughly and uniformly mixed are mutually and closely contacted, ions near the contact surface at high temperature have enough energy to get rid of the constraint of the inherent lattice points and diffuse, and a layer of hexagonal K is locally generated on the contact surface through further structural rearrangement 0.8-2x-2y Ba 0.1+x Eu y Al 11 O 17 (nucleus) and then gradually growing as the reaction time increases, resulting in the substantial formation of K 0.8-2x-2y Ba 0.1+x Eu y Al 11 O 17 A product phase.
K 0.8-2x-2y Ba 0.1+x Eu y Al 11 O 17 (wherein 0. ltoreq. x.ltoreq.0.3; 0.025. ltoreq. y.ltoreq.0.175) is a hexagonal system which exhibits a typical beta-Al 2 O 3 A structure consisting of a spinel layer and Ba/KO 9 Layers are alternately arranged, activator Eu 2+ Is expected to enter Ba/KO 9 Ba/K sites of the layer, substituted for Ba 2+ Or K + Thereby the prepared fluorescent powder has luminous performance. K 0.8-2x- 2y Ba 0.1+x Eu y Al 11 O 17 (wherein x is 0. ltoreq. x.ltoreq.0.3; y is 0.025. ltoreq. y.ltoreq.0.175) has a metal cation defect structure V K ’ The existence of such a defective structure has a certain relationship with thermal stability, specifically: when using Ba 2+ Substituted K + To satisfy the compoundConservation of charge of (1) will form K + Vacancy defect, Ba 2+ The greater the content, K + The greater the number of vacancy defects. K is + The vacancy defects can form defect energy levels in the band gap of the material, and the energy level positions of the vacancy defects are close to the conduction band bottom, so that when the blue fluorescent powder is applied to white light LED illumination, the defect energy levels can store photons in a photoluminescence process; with the rise of the external environment temperature, under the action of thermal disturbance, the defect energy level releases photons at a higher temperature, and the speed of storing and releasing the photons is dependent on the temperature. Thus, K + The presence of defects can affect the rate of photon release at different temperatures, thereby controlling the luminous intensity of the material at different temperatures. Controlling K in a material by varying the value of x + The number of defects can improve the thermal quenching performance of the material, so that the luminous intensity of the material at high temperature is kept close to that at room temperature.
The invention has the beneficial effects that:
1) the blue fluorescent powder has high quantum efficiency (the internal quantum efficiency is more than 90 percent), the thermal stability is superior to that of the prior blue commercial fluorescent powder, and the emission intensity of the fluorescent powder is basically unchanged along with the temperature rising from room temperature to 200 ℃.
2) The blue fluorescent powder has a wide excitation band (250nm-430nm), can be effectively excited by ultraviolet light and near ultraviolet light, has strong absorption in a near ultraviolet band of 300-400nm, emits blue light with a main peak of about 450nm, has high color purity, and has high matching degree with an emission spectrum of a near ultraviolet chip.
3) The blue fluorescent powder is prepared by adopting a high-temperature solid-phase method, has simple and easy preparation process, low cost, no toxicity and no pollution, and can be industrially produced.
Drawings
FIG. 1 is an XRD spectrum of a blue phosphor prepared in example 1;
FIG. 2 shows the excitation and emission spectra of the blue phosphor prepared in example 1;
FIG. 3 is a graph showing the change of emission intensity with temperature of the blue phosphor prepared in example 1, with an excitation wavelength of 365 nm.
Detailed Description
The present invention will now be further described with reference to the following detailed description and the accompanying drawings, which are illustrative, but not limiting, of the invention.
Example 1
(1) According to K 0.6 Ba 0.1 Eu 0.1 Al 11 O 17 In the stoichiometric ratio of the chemical compositions, 0.2225gK is weighed 2 CO 3 、 0.15884gBaCO 3 、4.51387gAl 2 O 3 、0.0708gEu 2 O 3 And 0.2gAlF 3 As a raw material;
(2) fully grinding the raw materials, and uniformly mixing to obtain a mixture;
(3) placing the mixture in a corundum crucible, then placing the corundum crucible into a tube furnace, and introducing 5% of H by volume percentage 2 And 95% of N 2 Heating to 900 ℃ at the heating rate of 5 ℃/min under the condition of the formed reducing atmosphere, preserving heat for 2 hours to promote the decomposition of carbonate, then heating to 1400 ℃ at the same heating rate, preserving heat for 6 hours, and naturally cooling to room temperature to obtain a sinter;
(4) and grinding the sintered substance into powder, and sieving the powder by using a 300-mesh sieve to obtain the blue fluorescent powder.
FIG. 1 is an XRD spectrum of the blue phosphor prepared in example 1, and it can be seen from FIG. 1 that the blue phosphor has beta-Al 2 O 3 KAl of structure 11 O 17 Compared with a standard card, the blue fluorescent powder has good matching and higher diffraction peak intensity, which indicates that the blue fluorescent powder has the characteristics of KAl 11 O 17 Uniform beta-Al 2 O 3 Crystal structure and no other impurity phase.
FIG. 2 is the excitation and emission spectra of the blue phosphor prepared in example 1, and it can be seen from FIG. 2 that the blue phosphor absorbs light (250-430nm) from the ultraviolet region to the visible region, indicating that the blue phosphor has a wide excitation band; meanwhile, the blue fluorescent powder emits blue light with a main peak at 450nm under the excitation of 365nm near ultraviolet light, which indicates that the fluorescent powder prepared by the preparation method is the blue fluorescent powder.
Fig. 3 is a graph showing the change of the fluorescence emission intensity of the blue phosphor prepared in example 1 with the temperature under the excitation of 365nm near ultraviolet light, and it can be seen from fig. 3 that when the temperature is increased from 25 ℃ to 225 ℃, the emission intensity of the blue phosphor has little fluctuation and does not significantly decrease, the overall intensity tends to be stable, and the thermal stability is better.
Example 2
(1) According to K 0.4 Ba 0.2 Eu 0.1 Al 11 O 17 In the stoichiometric ratio of the chemical compositions, 0.14833gK is weighed 2 CO 3 、 0.31768gBaCO 3 、4.51387gAl 2 O 3 、0.0708gEu 2 O 3 And 0.2gAlF 3 As a raw material;
(2) fully grinding the raw materials, and uniformly mixing to obtain a mixture;
(3) placing the mixture in a corundum crucible, then placing the corundum crucible into a tube furnace, and introducing 5% of H by volume percentage 2 And 95% of N 2 Heating to 900 ℃ at the heating rate of 5 ℃/min under the condition of the formed reducing atmosphere, preserving heat for 2h to promote the decomposition of carbonate, then heating to 1400 ℃ at the same heating rate, preserving heat for 6h, and naturally cooling to room temperature to obtain a sinter;
(4) and grinding the sintered substance into powder, and sieving the powder by a 300-mesh sieve to obtain the blue fluorescent powder.
Example 3
(1) According to K 0.2 Ba 0.3 Eu 0.1 Al 11 O 17 0.22250g K is weighed according to the stoichiometric ratio of the chemical components 2 CO 3 、 0.47652gBaCO 3 、4.51387gAl 2 O 3 、0.0708gEu 2 O 3 And 0.2gAlF 3 As a raw material;
(2) fully grinding the raw materials, and uniformly mixing to obtain a mixture;
(3) placing the mixture in a corundum crucible, then placing the corundum crucible into a tube furnace, and introducing 5% of H by volume percentage 2 And 95% of N 2 Heating to 900 deg.C at a rate of 5 deg.C/min under reducing atmosphere, and maintainingHeating for 2h to promote the decomposition of carbonate, then heating to 1400 ℃ at the same heating rate, preserving heat for 6h, and naturally cooling to room temperature to obtain a sinter;
(4) and grinding the sinter into powder, and sieving the powder with a 300-mesh sieve to obtain the blue fluorescent powder.
Example 4
(1) According to K 0.45 Ba 0.1 Eu 0.175 Al 11 O 17 In the stoichiometric ratio of the chemical compositions, 0.16688gK is weighed 2 CO 3 、 0.15884gBaCO 3 、4.51387gAl 2 O 3 、0.1239gEu 2 O 3 And 0.2gAlF 3 As a raw material;
(2) fully grinding the raw materials, and uniformly mixing to obtain a mixture;
(3) placing the mixture in a corundum crucible, then placing the corundum crucible into a tube furnace, and introducing 5% of H by volume percentage 2 And 95% of N 2 Heating to 900 ℃ at the heating rate of 5 ℃/min under the condition of the formed reducing atmosphere, preserving heat for 2h to promote the decomposition of carbonate, then heating to 1400 ℃ at the same heating rate, preserving heat for 6h, and naturally cooling to room temperature to obtain a sinter;
(4) and grinding the sinter into powder, and sieving the powder by using a 300-mesh sieve to obtain the fluorescent powder.
Claims (1)
1. beta-Al activated by europium 2 O 3 The preparation method of the blue fluorescent powder with the defect structure is characterized in that the chemical structural formula of the blue fluorescent powder is K 0.8-2x-2y Ba 0.1+x Eu y Al 11 O 17 Wherein x is more than or equal to 0 and less than or equal to 0.3; y is more than or equal to 0.025 and less than or equal to 0.175;
the method is specifically carried out according to the following steps:
step 1: according to the chemical formula K 0.8-2x-2y Ba 0.1+x Eu y Al 11 O 17 Weighing carbonate or nitrate containing K, Ba and oxide containing Al and Eu according to the stoichiometric ratio of the chemical compositions; weighing a fluxing agent;
step 2: grinding the raw materials in the step 1, and uniformly mixing to obtain a mixture;
and step 3: carrying out sectional sintering on the mixture obtained in the step 2 under the condition of introducing a reducing atmosphere, and then cooling to room temperature to obtain a sintered material;
and 4, step 4: grinding the sinter obtained in the step 3 into powder, and sieving the powder by using a sieve of 300-600 meshes to obtain blue fluorescent powder;
in the step 1, the fluxing agent is AlF 3 、BaF 2 、H 3 BO 3 、CaF 2 One or more of the above; the adding amount of the fluxing agent is 3-5% of the total mass of the raw materials;
in the step 3, the reducing atmosphere is composed of 5-10% of H in percentage by volume 2 And 95 to 90% of N 2 Forming;
the segmented sintering in the step 3 comprises the following steps: firstly, raising the temperature to 900 ℃ at the temperature rise rate of 5 ℃/min, and preserving the temperature for 1-2 h; then the temperature is raised to 1400 ℃ and 1600 ℃ at the temperature raising rate of 5 ℃/min, and the temperature is preserved for 4 to 8 hours.
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