CN101575511A - Alkaline earth halide silicate green phosphor powder used for white light LED and preparation method thereof - Google Patents

Abstract

The invention provides an alkaline earth halosilicate green fluorescent powder for white light LEDs and a preparation method thereof. The chemical composition of the fluorescent powder is: xBaO-yBaX ₂ -2SiO ₂ :zEu ²⁺ , where x=1-8, y=0.5-3, z=0.01-3, and X is Cl or Br. The alkaline earth halosilicate fluorescent powder can be obtained by pre-calcining the weighed raw materials at 400-600° C. for 3-8 hours and sintering at 700-1000° C. for 4-10 hours. The fluorescent powder of the invention can effectively absorb near ultraviolet light and blue light of 280-480nm, and effectively emit long-wave visible light with a peak wavelength of 500-510nm, and is a new type of fluorescent powder suitable for the application of white light LED devices.

Description

Alkaline earth halosilicate green fluorescent powder for white light LED and preparation method thereof

technical field

The invention relates to a fluorescent material for violet and blue LEDs and a preparation method thereof. Specifically, the present invention relates to an alkaline earth halosilicate green fluorescent powder that can be excited by 280-480nm purple light and blue light LED and a preparation method thereof.

Background technique

GaN-based light-emitting diode (Light Emitting Diode) is a new type of light-emitting device with small size, low calorific value, low power consumption, long life (more than 10,000 hours), fast response (can be operated at high frequency), Environmental protection (shock resistance, impact resistance, unbreakable, recyclable waste) and planar packaging, easy to develop into thin and compact products, etc., can be widely used in various lighting facilities, including indoor lights, traffic lights, traffic lights, Street lamps, tail lights for automobiles, super large screens for outdoor use, display screens and advertising boards, etc., can also be used as indicator lights for various instruments and meters. This new type of light source will surely become a new generation of light source in the 21st century, which is of great significance to energy saving, environmental protection, and improvement of people's quality of life.

At present, the method of LED to achieve white light is mainly: coating the blue LED chip with yellow phosphor powder that can be excited by blue light, and the blue light and yellow light are mixed to form white light; or coating the blue LED chip that is excited by blue light to emit green light Phosphor powder of light and red light, red light, blue light, and green light are mixed to form white light; or near-ultraviolet light and blue light LED chips are coated with efficient three-color phosphor powder to make white light LED.

At present, the most active research in various countries in the world is the combination of a single LED chip and a phosphor to emit light. The earliest commercialized white light LED was Japan's Nichia company, which used the blue light (about 450nm) emitted by GaN-based LED chips to excite the rare earth phosphor YAG: Ce ³⁺ to emit yellow light. The emission wavelength of the current InGaN chip has been blue-shifted to the near ultraviolet region, which can provide higher excitation energy for the phosphor. However, there are not many phosphors available for white LEDs at present. The absorption peak of light conversion materials based on blue LEDs is required to be located at 420-470nm. There are very few fluorescent materials that can meet this requirement, and the absorption intensity is not very large. The exploration of quasi-fluorescent materials is quite difficult. In addition, phosphors that can be used for excitation of purple tubes (UV-LED) around 400nm cannot match UV-LEDs well in terms of excitation wavelength, such as blue phosphor BaMgAl ₁₀ O ₁₇ :Eu ⁺ (BAM) for commercial LEDs The absorption at 400nm is not strong, so it cannot meet the needs of UV-LED well.

Contents of the invention

The object of the present invention is to provide a novel alkaline earth halosilicate green fluorescent powder, which can be excited by 280-480nm purple and blue LEDs, has high light conversion efficiency, and can emit light stably. It emits long-wave visible light of 500-510nm.

Another object of the present invention is to provide a preparation method of the novel alkaline earth halosilicate green fluorescent powder.

The inventors of the present invention have found that the BaO-BaX ₂ -SiO ₂ :Eu ²⁺ system fluorescent material can be excited by violet and blue LEDs through a large number of experiments and theoretical studies, and has high light conversion efficiency and can stably emit green fluorescence . The inventors of the present invention further obtained the preparation method of the novel alkaline earth halosilicate green phosphor powder of the present invention by determining the appropriate raw material ratio of the novel alkaline earth halosilicate green phosphor powder and the sintering temperature of the phosphor powder.

The chemical composition formula of alkaline earth halosilicate green fluorescent powder for white light LED of the present invention is:

xBaO-yBaX ₂ -2SiO ₂ :zEu ²⁺ (1)

In formula (1), x=1-8, y=0.5-3, z=0.01-0.3, and X is Cl or Br.

The alkaline earth halosilicate green fluorescent powder for white light LEDs of the present invention is prepared by a traditional high-temperature solid-phase method. Specifically, the method includes:

(1) According to the chemical composition of the above formula (1): xBaO-yBaX ₂ -2SiO ₂ : zEu ²⁺ , weigh the stoichiometric ratio of alkaline earth halide BaX ₂ , rare earth oxide Eu ₂ O ₃ or generate rare earth Europium salt of the oxide Eu ₂ O ₃ , alkaline earth oxide BaO, or barium salt to generate alkaline earth oxide BaO on heating, and ground for homogeneous mixing;

(2) Pre-calcining the uniformly mixed material in air at 400-600° C. for 3-8 hours;

(3) cooling the pre-calcined material to room temperature, and grinding and pulverizing;

(4) Sintering the ground material at 700-1000° C. for 4-10 hours under a reducing atmosphere;

(5) Cooling the sintered material to room temperature, grinding, pulverizing and sieving to obtain the alkaline earth halosilicate phosphor.

Compared with the prior art, the alkaline earth halosilicate phosphor of the present invention has a very wide excitation spectrum, has strong absorption in the range of 280-480nm (especially around 400nm), and effectively emits a peak wavelength at 500-480nm. The 510nm long-wave visible light is a new type of phosphor suitable for the application of white light LED devices.

In addition, the alkaline earth silicate fluorescent powder of the present invention has strong emission intensity of long-wave visible light, and uses common halosilicate as a matrix, and the synthetic method of the fluorescent powder is simple and easy to operate.

Description of drawings

Fig. 1 is the room temperature excitation and emission spectrum of the 4BaO-BaCl ₂ -2SiO ₂ :0.1Eu ²⁺ phosphor of the present invention;

Fig. 2 is the room temperature excitation and emission spectrum of the 4BaO-BaBr ₂ -2SiO ₂ :0.05Eu ²⁺ phosphor of the present invention;

Fig. 3 is the excitation and emission spectra at room temperature of 3BaO-BaBr ₂ -2SiO ₂ :0.01Eu ²⁺ phosphor powder of the present invention;

Fig. 4 is the room temperature excitation and emission spectrum of the 3BaO-BaCl ₂ -2SiO ₂ :0.16Eu ²⁺ phosphor of the present invention;

Fig. 5 is the room temperature excitation and emission spectrum of the 5BaO-1.5BaCl ₂ -2SiO ₂ :0.01Eu ²⁺ phosphor of the present invention;

Fig. 6 is the excitation and emission spectra at room temperature of the 5BaO-1.5BaBr ₂ -2SiO ₂ :0.16Eu ²⁺ phosphor powder of the present invention.

Detailed ways

The present invention is described in detail below.

The chemical composition formula of the alkaline earth halosilicate green fluorescent powder for white light LED of the present invention is: xBaO-yBaX ₂ -2SiO ₂ :zEu ²⁺ . Usually, the molar weight x of BaO in the chemical composition formula is 1-8, preferably 2-7, more preferably 2.5-6, most preferably any value in 3-5, for example, the molar weight x of BaO can be 3 , 3.5, 4, 4.5 and 5. The molar weight y of _BaX2 (where X is Cl or Br) in the chemical composition formula is 0.5-3, preferably 1.0-2.5, more preferably 1.0-2.0, most preferably any value in 1.0-1.5, for example The molar amount y of BaX ₂ can be 1.0, 1.5 and 2.0.

The molar amount z of the rare earth ion Eu ²⁺ doped in the alkaline earth halosilicate fluorescent powder of the present invention is usually 0.01 to 0.30 moles, preferably 0.01 to 0.20, most preferably any value in 0.01 to 0.16, for example, Rare earth ion doping amount z is 0.01, 0.05, 0.1, 0.16 and 0.20.

The alkaline earth halosilicate green fluorescent powder for white LEDs of the present invention is prepared by a traditional high-temperature solid-phase method. The method includes the steps of: weighing the stoichiometric ratio according to the chemical composition formula xBaO-yBaX ₂ -2SiO ₂ :zEu ²⁺ Alkaline earth halide BaX ₂ (where X is Cl or Br), rare earth oxide Eu ₂ O ₃ or europium salt of rare earth oxide Eu ₂ O ₃ under heating, alkaline earth oxide BaO or alkaline earth oxide under heating Barium salt of BaO, and grind to mix uniformly; pre-calcine the uniformly mixed material in air at 400-600°C for 3-8 hours; cool the pre-calcined material to room temperature, and grind and pulverize; grind the The material is sintered at 700-1000° C. for 4 to 10 hours under a reducing atmosphere; the sintered material is cooled to room temperature, ground, pulverized and sieved to obtain the alkaline earth halosilicate green fluorescent powder.

In the preparation method of the alkaline earth halosilicate fluorescent powder of the present invention, the alkaline earth halide _BaX used can be barium chloride or barium bromide salt, such as anhydrous barium chloride, dihydrate barium chloride, anhydrous Barium bromide, barium bromide dihydrate, etc. The raw material for barium oxide can be alkaline earth metal oxide BaO or a barium salt that generates alkaline earth metal oxide BaO under heating, such as BaCO ₃ , Ba(NO ₃ ) ₂ , or BaCO ₃ , Ba(NO ₃ ) ₂ The hydrate salt of BaO and the above-mentioned barium salt or a combination of multiple barium salts can also be used. The raw material used as the rare earth metal oxide Eu ₂ O ₃ may be Eu ₂ O ₃ or a europium salt that generates rare earth oxide Eu ₂ O ₃ under heating, such as europium nitrate and its hydrate salt. In addition, the silica raw material used may be any silica as long as it is silica in solid form, such as α-silica, β-silica, and λ-silica. All of the above-mentioned raw materials are preferably in powder form for thorough mixing prior to pre-calcination.

After accurately weighing the above raw materials, first grind and mix them uniformly, and then pre-calcine in air at 400-600°C for 3-8 hours, preferably at 500-600°C, more preferably at 500-550°C. 3 to 5 hours, preferably 3.5 to 4 hours for pre-calcination, more preferably 4 hours for pre-calcination. After pre-calcination, it is cooled to room temperature, ground and pulverized, and then sintered at 700-1000°C, preferably at 800-900°C, more preferably at 800°C for 4-10 hours, preferably 6-10 hours under reducing atmosphere. 8 hours, most preferably sintering for 8 hours. Then the sintered material is cooled to room temperature, ground, pulverized and sieved to obtain the required alkaline earth halosilicate phosphor powder for white light LED.

In addition, the reducing atmosphere used in the method of the present invention refers to the introduction of reducing gases during sintering, such as reducing hydrogen (H ₂ ), a mixture of nitrogen and hydrogen (N ₂ and H ₂ ), ammonia (NH ₃ ) or carbon monoxide gas; or by adding carbon powder to form a reducing atmosphere during sintering. According to one embodiment of the present invention, it is preferred to use a mixed gas of nitrogen and hydrogen or add carbon powder.

The alkaline earth halosilicate green fluorescent powder of the present invention has a very wide excitation spectrum, has strong absorption in the range of 280-480nm (especially around 400nm), and its emission main peak is located at 500-510nm, which is suitable for the application of white light LED devices. new phosphors. Since the alkaline earth halosilicate green fluorescent powder of the present invention adopts common halosilicate as a matrix and adopts a traditional solid-phase synthesis method, the synthesis method of the fluorescent powder is simple and easy to operate.

Example

The following specific examples are used to further explain and illustrate the present invention, but the following specific examples cannot be used to limit the protection scope of the present invention. Various changes and improvements of the following specific embodiments are included within the scope defined by the appended claims.

Example 1: Preparation of 4BaO-BaCl ₂ -2SiO ₂ :0.1Eu ²⁺ Phosphor Powder

Weigh 1.5788g barium carbonate (BaCO ₃ ), 0.4886g barium chloride dihydrate (BaCl ₂ 2H ₂ O), 0.2403g silicon dioxide (SiO ₂ ), 0.0352g europium oxide (Eu ₂ O ₃ ), and The above-mentioned raw material mixture is ground and mixed evenly in an agate mortar, then put into a corundum crucible, pre-calcined in air at 500°C for 4 hours, cooled to room temperature, taken out, ground and pulverized; then mixed with carbon powder as a reducing atmosphere sintered at 900°C for 5 hours, then kept at a constant temperature for 4 hours, cooled to room temperature, ground again, and sieved to obtain the phosphor sample above. The sample emits green light under the excitation of 391nm ultraviolet light. The room temperature excitation and emission spectra of the phosphor are shown in Figure 1.

Example 2: Preparation of 4BaO-BaBr ₂ -2SiO ₂ :0.05Eu ²⁺ Phosphor Powder

Weigh 1.5788g barium carbonate (BaCO ₃ ), 0.6664g barium bromide dihydrate (BaBr ₂ 2H ₂ O), 0.2403g silicon dioxide (SiO ₂ ), 0.0176g europium oxide (Eu ₂ O ₃ ), and The above-mentioned raw material mixture is ground and mixed evenly in an agate mortar, then put into a corundum crucible, pre-calcined in air at 500°C for 4 hours, cooled to room temperature, taken out, ground and pulverized; then mixed with carbon powder as a reducing atmosphere sintered at 900°C for 5 hours, then kept at a constant temperature for 4 hours, cooled to room temperature, ground again, and sieved to obtain the phosphor sample above. The sample emits green light under the excitation of 360nm ultraviolet light. The room-temperature excitation and emission spectra of the phosphor are shown in FIG. 2 .

Example 3: Preparation of 3BaO-BaBr ₂ -2SiO ₂ :0.01Eu ²⁺ Phosphor Powder

Weigh respectively 0.9200g barium oxide (BaO), 0.6664g barium bromide dihydrate (BaBr ₂ 2H ₂ O), 0.2403g silicon dioxide (SiO ₂ ), 0.0035g europium oxide (Eu ₂ O ₃ ), and the above The raw material mixture was ground and mixed evenly in an agate mortar, then loaded into a corundum crucible, pre-calcined in air at 600°C for 3 hours, cooled to room temperature, and taken out for grinding and pulverization; then hydrogen was used as a reducing atmosphere, at 800 Sintering at ℃ for 6 hours, then keeping the temperature for 4 hours, cooling to room temperature, grinding again, and sieving to finally obtain the above fluorescent powder sample. The sample emits green light under the excitation of 360nm ultraviolet light. The room temperature excitation and emission spectra of the phosphor are shown in FIG. 3 .

Example 4: Preparation of 3BaO-BaCl ₂ -2SiO ₂ :0.16Eu ²⁺ Phosphor Powder

Weigh respectively 0.9200g barium oxide (BaO), 0.4886g barium chloride dihydrate (BaCl ₂ 2H ₂ O), 0.2403g silicon dioxide (SiO ₂ ), 0.0563g europium oxide (Eu ₂ O ₃ ), and the above The raw material mixture was ground and mixed evenly in an agate mortar, then put into a corundum crucible, pre-calcined in air at 600°C for 3 hours, cooled to room temperature, taken out, ground and pulverized; Sintering at 800° C. for 6 hours, then keeping the temperature for 4 hours, cooling to room temperature, grinding again, and sieving to finally obtain the above phosphor powder sample. The sample emits green light under the excitation of 410nm ultraviolet light. The room temperature excitation and emission spectra of the phosphor are shown in FIG. 4 .

Example 5: Preparation of 5BaO-1.5BaCl ₂ -2SiO ₂ :0.01Eu ²⁺ Phosphor Powder

Weigh 1.9735g barium carbonate (BaCO ₃ ), 0.7328g barium chloride dihydrate (BaCl ₂ 2H ₂ O), 0.2403g silicon dioxide (SiO ₂ ), 0.1081 europium nitrate (Eu(NO ₃ ) ₃ ), Grind and mix the above raw material mixture evenly in an agate mortar, then put it into a corundum crucible, pre-calcine in air at 550°C for 4 hours, cool to room temperature, take it out and grind it; then pass the mixture gas of hydrogen and nitrogen As a reducing atmosphere, sinter at 850° C. for 6 hours, then keep the temperature for 4 hours, cool down to room temperature, grind again, and sieve to finally obtain the phosphor sample above. The sample emits green light under the excitation of 344nm ultraviolet light. The room temperature excitation and emission spectra of the phosphor are shown in FIG. 5 .

Example 6: Preparation of 5BaO-1.5BaBr ₂ -2SiO ₂ :0.16Eu ²⁺ Phosphor Powder

Weigh 1.9735g barium carbonate (BaCO ₃ ), 0.9995g barium bromide dihydrate (BaBr ₂ 2H ₂ O), 0.2403g silicon dioxide (SiO ₂ ), 0.1081g europium nitrate (Eu(NO ₃ ) ₃ ) , grind and mix the above-mentioned raw material mixture in an agate mortar, then put it into a corundum crucible, pre-calcine in air at 550°C for 4 hours, cool to room temperature, take it out and grind it; then pass in hydrogen and nitrogen as In a reducing atmosphere, sinter at 850° C. for 6 hours, then keep the temperature for 4 hours, cool down to room temperature, grind evenly again, and sieve to finally obtain the above-mentioned phosphor powder sample. The sample emits green light under the excitation of 342nm ultraviolet light. The room temperature excitation and emission spectra of the phosphor are shown in FIG. 6 .

Claims (10)

1. An alkaline earth halosilicate fluorescent powder, which is an alkaline earth halosilicate green fluorescent powder for white light LEDs, characterized in that, the chemical composition formula of the alkaline earth halosilicate fluorescent powder is: xBaO-yBaX ₂ -2SiO ₂ : zEu ²⁺ , where x=1-8, y=0.5-3, z=0.01-0.3, and X is Cl or Br. 2. The alkaline earth halosilicate fluorescent powder according to claim 1, characterized in that x=3～5, y=1～1.5, z= in the chemical composition formula of the alkaline earth halosilicate fluorescent powder 0.01～0.16. 3. The alkaline earth halosilicate fluorescent powder according to claim 1 or 2, characterized in that the chemical composition formula of the fluorescent powder is 4BaO—BaX ₂ —2SiO ₂ :0.10Eu ²⁺ . 4. A method for preparing the alkaline earth halosilicate fluorescent powder as claimed in claim 1-3, characterized in that the method comprises: (1) According to the chemical composition formula, weigh the stoichiometric _ratio of alkaline earth halide BaX ₂ , rare earth oxide Eu ₂ O ₃ or europium salt, alkaline earth oxide _BaO or Barium salt of alkaline earth oxide BaO is formed under heating and ground to mix uniformly; (2) Pre-calcining the uniformly mixed material in air at 400-600°C for 3-8 hours; (3) cooling the pre-calcined material to room temperature, and grinding and pulverizing; (4) Sintering the ground material at 700-1000° C. for 4-10 hours under a reducing atmosphere; (5) Cooling the sintered material to room temperature, grinding, pulverizing and sieving to obtain the alkaline earth halosilicate phosphor. 5 . The method according to claim 4 , wherein the reducing atmosphere is hydrogen (H ₂ ), a mixture of hydrogen and nitrogen (N ₂ and H ₂ ), ammonia (NH ₃ ) or carbon monoxide. 6. The method according to claim 4, wherein the reducing atmosphere is an atmosphere generated by adding carbon powder. 7. The method according to any one of claims 4-6, characterized in that, the europium salt is europium nitrate, and the barium salt is barium carbonate or barium nitrate. 8. The method according to any one of claims 4-7, characterized in that, the temperature of the pre-calcination is 500-600°C, and the temperature of the sintering is 800-900°C. 9. The method according to any one of claims 4-8, characterized in that, the pre-calcination time is 3-5 hours, and the sintering time is 6-8 hours. 10. The method according to any one of claims 4-9, characterized in that the pre-calcination temperature is 500°C, the pre-calcination time is 4 hours, and the sintering temperature is 800°C , the sintering time is 6 hours.

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