CN111187622B - Single matrix phosphate fluorescent powder for white light LED and preparation method thereof - Google Patents

Abstract

The invention discloses a single matrix phosphate fluorescent powder for a white light LED and a preparation method thereof. The fluorescent powder has the following chemical composition general formula: (SrCa) _x1.98‑2 La _y1‑ (PO ₄ ) ₃ O:0.04Eu ²⁺ ,yTb ³⁺ ,4xMn ²⁺ Wherein, 0.ltoreq.0x≤0.15,0≤yAnd (3) weighing the raw materials according to the stoichiometric ratio, mixing, grinding and drying, and then sintering at high temperature in a reducing atmosphere in a tubular furnace to obtain the high-temperature sintering furnace. The fluorescent powder can emit white light under the excitation of near ultraviolet light, is suitable for various illumination display devices taking the near ultraviolet light as an excitation source, and has high luminous intensity and good color rendering. The preparation method provided by the invention is simple, easy to operate, low in production cost and suitable for large-scale production.

Description

Single matrix phosphate phosphor for white light LED and preparation method thereof

Technical field

The invention belongs to the technical field of luminescent materials and relates to a near-ultraviolet light-excited single-matrix phosphate phosphor and a preparation method.

Background technique

As human awareness of energy conservation and environmental protection continues to strengthen, the need to reduce carbon emissions has promoted the use of renewable energy or energy-saving smart devices. Solid State Lighting (SSL), represented by semiconductor light-emitting diodes (LED), emerged as the times require and has become the fourth generation lighting source. Solid-state lighting has the advantages of small size, environmental protection, energy saving, high efficiency, and long life. It is conducive to the sustainable development of society and has become the preferred lighting method in today's society that pursues a low-carbon economy. White LED is the top priority of solid-state lighting, and how to obtain high-quality white light has become the key technology of solid-state lighting.

Currently, commercial white LED lighting devices are mostly packaged using a combination of blue LED chips and yellow phosphor YAG: Ce ³⁺ . However, since the white light produced by this method lacks the red light component, it has the disadvantages of low color rendering index (CRI~70−80) and high correlated color temperature (CCT~7750 K). How to improve these shortcomings and obtain a white light source with high color rendering quality has become the goal pursued by many researchers.

In recent years, among the many solutions for producing white light, two categories have received relatively more attention. First, the ultraviolet or near-ultraviolet LED chip is packaged with the three primary colors of red, green and blue phosphors mixed in a certain proportion. After the three primary colors are mixed, white light emission can be obtained. By fine-tuning the ratio of red, green and blue phosphors, the color temperature and color rendering index can be adjusted. The production cost of this method is relatively high, and there are problems with different reabsorption and aging rates between phosphors, which greatly affects the lumen efficiency and color reproducibility of the device. Another, more feasible solution uses ultraviolet or near-ultraviolet light to excite phosphors with a single matrix to obtain white light. The three primary colors of red, green and blue are taken on by different ion luminescence centers. With the help of the regulation of fluorescence spectrum by energy transfer between ions, the luminescent color of phosphors can be adjusted by changing the concentration ratio of different luminescent center ions, thus ultimately achieving white light emission at a specific ratio. Using a single matrix white light phosphor can simplify the LED device packaging process while improving lumen efficiency and color rendering index. Therefore, it is of great value to develop single-matrix white-light phosphors with high luminescence properties.

Contents of the invention

The object of the present invention is to provide a single-matrix phosphate phosphor for white LED that can be excited by near-ultraviolet light and a preparation method thereof.

The technical solution adopted by the present invention is: a single matrix phosphate phosphor for white light LED, whose general chemical formula is: (SrCa) _{1.98-2 x} La _{1- y} (PO ₄ ) ₃ O: 0.04Eu ²⁺ , y Tb ³⁺ , 4 x Mn ²⁺ , where 0 ≤ x ≤ 0.15, 0 ≤ y ≤ 0.20, x and y cannot be 0 at the same time.

Preferably, 0.10 ≤ x ≤ 0.125, 0.05 ≤ y ≤ 0.10.

Better, x = 0.10, 0.05 ≤ y ≤ 0.10.

Another technical solution adopted by the present invention is: a preparation method of the above-mentioned phosphor, which is specifically carried out according to the following steps:

(1) Weigh the raw materials SrCO ₃ , CaCO ₃ , (NH ₄ ) ₂ HPO ₄ , La ₂ O ₃ , Eu ₂ O ₃ , Tb ₄ O ₇ and MnCO ₃ according to the stoichiometric ratio of the general chemical formula of the phosphor;

(2) Add cosolvent to the above raw materials, place in a mortar, mix and grind evenly;

(3) Pre-calcine the mixture obtained in step (2) at 600°C for 3 hours, naturally cool to room temperature, take it out and grind again, calcine at 1200°C for 3 hours in a weak reducing atmosphere, and then cool to room temperature in the furnace;

(4) Grind and sieve the sintered product obtained in step (3) to prepare the phosphor.

Preferably, the flux is Li ₂ CO ₃ .

Preferably, the amount of co-solvent added is 2% of the raw material mass.

Preferably, the weak reducing atmosphere refers to an atmosphere of 5% H ₂ /95% N ₂ (volume ratio).

Compared with the existing technology, the beneficial effects of the present invention are: the preparation method of the present invention is simple, easy to operate, low cost, and environmentally friendly, and the prepared (SrCa) _{1.98-2 x} La _{1- y} (PO ₄ ) ₃ O: 0.04 Eu ²⁺ , y Tb ³⁺ , 4 x Mn ²⁺ (0 ≤ x ≤ 0.15, 0≤ y ≤ 0.20) The luminescence color of the phosphor under near-ultraviolet light excitation can be tunable, that is, when the value of x or y is controlled When x and y change, the luminescent color of the phosphor will change. When x and y take specific values (0.10 ≤ It has the advantage of stable chemical properties, and can achieve light color control by adjusting the ion concentration ratio.

In addition to the objects, features and advantages described above, the present invention has other objects, features and advantages. The present invention will be described in further detail below with reference to the drawings.

Description of the drawings

Figure 1 is a comparison chart between the X-ray diffraction pattern and the standard pattern of the phosphors prepared in Examples 1 to 4 of the present invention.

Figure 2 is the excitation spectrum of the phosphor prepared in Example 3 of the present invention.

Figure 3 is a schematic diagram of the energy transfer process between ions in the preparation of phosphors in Examples 1 to 4 of the present invention.

Figure 4 is the emission spectrum of the phosphor prepared in Examples 1 to 4 of the present invention.

Figure 5 is the CIE chromaticity coordinates of the phosphors prepared in Examples 1 to 4 of the present invention.

Figure 6 is the emission spectrum of the phosphor prepared in Example 7 of the present invention.

Figure 7 is the emission spectrum of the phosphor prepared in Example 8 of the present invention.

Detailed ways

The present invention will be described in detail below with reference to the drawings and specific embodiments.

Example 1

(1) According to the chemical formula (SrCa) _1.73 La _0.90 (PO ₄ ) ₃ O: 0.04Eu ²⁺ , 0.10Tb ³⁺ , 0.50Mn ²⁺ , according to the elements Sr, Ca, La, P, O, Eu, Tb, Mn _{The atomic molar ratio of 2} O ₃ (99.99%), Eu ₂ O ₃ (99.99%), Tb ₄ O ₇ (99.99%) and MnCO ₃ (99.95%). Add 2% raw material mass fraction of Li ₂ CO ₃ (99.99%) as a flux. Place the weighed materials in a mortar, add an appropriate amount of absolute ethanol, mix thoroughly and grind evenly to obtain a mixed material.

(2) Place the mixed material obtained in step (1) into a high-purity alumina crucible, place it in a low-temperature muffle furnace, and pre-sinter at 600°C for 3 hours. After the temperature naturally drops to room temperature, take it out, grind it fully again, put it into a high-temperature tube furnace, and calcine it at 1200°C for 3 hours in a weak reducing atmosphere of 5% H ₂ /95% N ₂ , with a heating rate of 6°C/ min.

(3) After natural cooling to room temperature in the furnace, take out the sintered product, grind and sieve to obtain the target product.

Example 2

(1) According to the chemical formula (SrCa) _1.78 La _0.90 (PO ₄ ) ₃ O: 0.04Eu ²⁺ , 0.10Tb ³⁺ , 0.40Mn ²⁺ , according to the elements Sr, Ca, La, P, O, Eu, Tb, Mn _{The atomic molar ratio of 2} O ₃ (99.99%), Eu ₂ O ₃ (99.99%), Tb ₄ O ₇ (99.99%) and MnCO ₃ (99.95%). Add 2% raw material mass fraction of Li ₂ CO ₃ (99.99%) as a flux. Place the weighed materials in a mortar, add an appropriate amount of absolute ethanol, mix thoroughly and grind evenly to obtain a mixed material.

(2) Place the mixed material obtained in step (1) into a high-purity alumina crucible, place it in a low-temperature muffle furnace, and pre-sinter at 600°C for 3 hours. After the temperature naturally drops to room temperature, take it out, grind it fully again, put it into a high-temperature tube furnace, and calcine it at 1200°C for 3 hours in a weak reducing atmosphere of 5% H ₂ /95% N ₂ , with a heating rate of 6°C/ min.

(3) After natural cooling to room temperature in the furnace, take out the sintered product, grind and sieve to obtain the target product.

Example 3

(1) According to the chemical formula (SrCa) _1.78 La _0.92 (PO ₄ ) ₃ O: 0.04Eu ²⁺ , 0.08Tb ³⁺ , 0.40Mn ²⁺ , according to the elements Sr, Ca, La, P, O, Eu, Tb, Mn _{The atomic molar ratio of 2} O ₃ (99.99%), Eu ₂ O ₃ (99.99%), Tb ₄ O ₇ (99.99%) and MnCO ₃ (99.95%). Add 2% raw material mass fraction of Li ₂ CO ₃ (99.99%) as a flux. Place the weighed materials in a mortar, add an appropriate amount of absolute ethanol, mix thoroughly and grind evenly to obtain a mixed material.

(2) Place the mixed material obtained in step (1) into a high-purity alumina crucible, place it in a low-temperature muffle furnace, and pre-sinter at 600°C for 3 hours. After the temperature naturally drops to room temperature, take it out, grind it fully again, put it into a high-temperature tube furnace, and calcine it at 1200°C for 3 hours in a weak reducing atmosphere of 5% H ₂ /95% N ₂ , with a heating rate of 6°C/ min.

(3) After natural cooling to room temperature in the furnace, take out the sintered product, grind and sieve to obtain the target product.

Example 4

(1) According to the chemical formula (SrCa) _1.78 La _0.95 (PO ₄ ) ₃ O: 0.04Eu ²⁺ , 0.05Tb ³⁺ , 0.40Mn ²⁺ , according to the elements Sr, Ca, La, P, O, Eu, Tb, Mn _{The atomic molar ratio of 2} O ₃ (99.99%), Eu ₂ O ₃ (99.99%), Tb ₄ O ₇ (99.99%) and MnCO ₃ (99.95%). Add 2% raw material mass fraction of Li ₂ CO ₃ (99.99%) as a flux. Place the weighed materials in a mortar, add an appropriate amount of absolute ethanol, mix thoroughly and grind evenly to obtain a mixed material.

(2) Place the mixed material obtained in step (1) into a high-purity alumina crucible, place it in a low-temperature muffle furnace, and pre-sinter at 600°C for 3 hours. After the temperature naturally drops to room temperature, take it out, grind it fully again, put it into a high-temperature tube furnace, and calcine it at 1200°C for 3 hours in a weak reducing atmosphere of 5% H ₂ /95% N ₂ , with a heating rate of 6°C/ min.

(3) After natural cooling to room temperature in the furnace, take out the sintered product, grind and sieve to obtain the target product.

The X'TRA type X-ray diffractometer of Swiss ARL Company was used to perform X-ray diffraction on the phosphors prepared in Examples 1 to 8. The radiation source was Cu target Kα1 radiation ( λ = 1.5406 Å), and the diffraction pattern was obtained ( ( , obtain the fluorescence spectrum of the phosphor.

Figure 1 is the XRD pattern of the phosphor prepared in Examples 1 to 4 of the present invention. By comparison with the standard card JCPDS # 44-0180, it can be seen that the phosphors prepared in Examples 1 to 4 all have pure phase structures, and the lattice structure is not changed after Eu ²⁺ , Tb ³⁺ , and Mn ²⁺ ions are incorporated into the crystal lattice. Significant distortion occurs.

Figure 2 shows the excitation spectrum of the phosphor prepared in Example 3 of the present invention. The monitoring wavelengths are 455 nm, 538 nm and 630 nm respectively. It can be seen from the figure that the excitation spectrum of the prepared phosphor has the characteristics of a broadband spectrum, and the excitation wavelength is distributed between 280 nm and 440 nm. It shows that the prepared phosphor can be effectively excited by ultraviolet and near-ultraviolet light, and is suitable for white light LED devices excited by ultraviolet/near-ultraviolet LED chips.

Figure 3 is a schematic diagram of the energy transfer process between Eu ²⁺ , Tb ³⁺ , and Mn ²⁺ ions in the preparation of phosphors in Examples 1 to 6 of the present invention. When excited by near-ultraviolet light, the energy transfer between ions can promote the simultaneous production of blue, green and red luminescence. When the molar concentrations of the three luminescent center ions meet a specific ratio, that is (SrCa) _{1.98-2 x} La _{1- y} (PO ₄ ) ₃ O: 0.04Eu ²⁺ , y Tb ³⁺ , 4 x Mn ²⁺ , 0.10 When ≤ x ≤ 0.125, 0.05 ≤ y ≤ 0.10, the phosphor can obtain white light emission under 365 nm near-ultraviolet light excitation.

Figure 4 shows the emission spectrum of the phosphors prepared in Examples 1 to 4 of the present invention under 365 nm near-ultraviolet light excitation. It can be seen from the figure that the emission spectrum of the phosphor co-doped with Eu ²⁺ , Tb ³⁺ and Mn ²⁺ ions contains the characteristic spectra of three luminescent centers, which are located in the blue, green and red bands respectively. The spectral peaks of each band are The wavelengths are respectively located at 455 nm, 538 nm and 630 nm, and the synthetic light appears white.

Figure 5 is a CIE chromaticity coordinate diagram of the phosphors prepared in Examples 1 to 4 of the present invention and a photo of the phosphor prepared in Example 3 under 365nm near-ultraviolet lamp irradiation. The chromaticity coordinates of the prepared phosphors are all located in the warm white area, and the phosphors emit bright warm white light.

Example 5

(1) According to the chemical formula (SrCa) _1.78 La _0.97 (PO ₄ ) ₃ O: 0.04Eu ²⁺ , 0.03Tb ³⁺ , 0.40Mn ²⁺ , according to the elements Sr, Ca, La, P, O, Eu, Tb, Mn _{The atomic molar ratio of 2} O ₃ (99.99%), Eu ₂ O ₃ (99.99%), Tb ₄ O ₇ (99.99%) and MnCO ₃ (99.95%). Add 2% raw material mass fraction of Li ₂ CO ₃ (99.99%) as a flux. Place the weighed materials in a mortar, add an appropriate amount of absolute ethanol, mix thoroughly and grind evenly to obtain a mixed material.

(2) Place the mixed material obtained in step (1) into a high-purity alumina crucible, place it in a low-temperature muffle furnace, and pre-sinter at 600°C for 3 hours. After the temperature naturally drops to room temperature, take it out, grind it fully again, put it into a high-temperature tube furnace, and calcine it at 1200°C for 3 hours in a weak reducing atmosphere of 5% H ₂ /95% N ₂ , with a heating rate of 6°C/ min.

(3) After natural cooling to room temperature in the furnace, take out the sintered product, grind and sieve to obtain the target product.

The XRD pattern, excitation spectrum, and emission spectrum under 365 nm near-ultraviolet light excitation of the phosphor sample prepared in this example are all similar to Example 1.

Example 6

(1) According to the chemical formula (SrCa) _1.78 La _0.85 (PO ₄ ) ₃ O: 0.04Eu ²⁺ , 0.15Tb ³⁺ , 0.40Mn ²⁺ , according to the elements Sr, Ca, La, P, O, Eu, Tb, Mn _{The atomic molar ratio of 2} O ₃ (99.99%), Eu ₂ O ₃ (99.99%), Tb ₄ O ₇ (99.99%) and MnCO ₃ (99.95%). Add 2% raw material mass fraction of Li ₂ CO ₃ (99.99%) as a flux. Place the weighed materials in a mortar, add an appropriate amount of absolute ethanol, mix thoroughly and grind evenly to obtain a mixed material.

(2) Place the mixed material obtained in step (1) into a high-purity alumina crucible, place it in a low-temperature muffle furnace, and pre-sinter at 600°C for 3 hours. After the temperature naturally drops to room temperature, take it out, grind it fully again, put it into a high-temperature tube furnace, and calcine it at 1200°C for 3 hours in a weak reducing atmosphere of 5% H ₂ /95% N ₂ , with a heating rate of 6°C/ min.

(3) After natural cooling to room temperature in the furnace, take out the sintered product, grind and sieve to obtain the target product.

The XRD pattern, excitation spectrum, and emission spectrum under 365 nm near-ultraviolet light excitation of the phosphor sample prepared in this example are all similar to Example 1.

Example 7

(1) According to the chemical formula (SrCa) _1.98 La _0.80 (PO ₄ ) ₃ O: 0.04Eu ²⁺ , 0.20Tb ³⁺ , the atomic molar ratio of Sr, Ca, La, P, O, Eu, and Tb elements is 1.98: 1.98: 0.80: 3: 13: 0.04: 0.20 Weigh the raw materials SrCO ₃ (99.00%), CaCO ₃ (99.00%), (NH ₄ ) ₂ HPO ₄ (99.00%), La ₂ O ₃ (99.99%), Eu ₂ O ₃ (99.99%) and Tb ₄ O ₇ (99.99%). Add 2% raw material mass fraction of Li ₂ CO ₃ (99.99%) as a flux. Place the weighed materials in a mortar, add an appropriate amount of absolute ethanol, mix thoroughly and grind evenly to obtain a mixed material.

(2) Place the mixed material obtained in step (1) into a high-purity alumina crucible, place it in a low-temperature muffle furnace, and pre-sinter at 600°C for 3 hours. After the temperature naturally drops to room temperature, take it out, grind it fully again, put it into a high-temperature tube furnace, and calcine it at 1200°C for 3 hours in a weak reducing atmosphere of 5% H ₂ /95% N ₂ , with a heating rate of 6°C/ min.

(3) After natural cooling to room temperature in the furnace, take out the sintered product, grind and sieve to obtain the target product.

The XRD pattern of the phosphor sample prepared in this example and the excitation spectrum under 538 nm green light monitoring are similar to Example 1. Figure 6 is the emission spectrum of the phosphor prepared in Example 7 of the present invention under the excitation of 365 nm near-ultraviolet light. It can be seen from Figure 6 that the emission spectrum of the phosphor co-doped with Eu ²⁺ and Tb ³⁺ ions contains the characteristic spectra of two luminescence centers, which are located in the blue and green bands respectively, and the spectral peak wavelengths are located at 455 nm and 538 nm respectively. nm, the synthetic light appears blue-green.

Example 8

(1) According to the chemical formula (SrCa) _1.68 La(PO ₄ ) ₃ O: 0.04Eu ²⁺ , 0.60Mn ²⁺ , the atomic molar ratio of Sr, Ca, La, P, O, Eu, and Mn elements is 1.68:1.68 : 1: 3: 13: 0.04: 0.60 Weigh the raw materials SrCO ₃ (99.00%), CaCO ₃ (99.00%), (NH ₄ ) ₂ HPO ₄ (99.00%), La ₂ O ₃ (99.99%), Eu ₂ O ₃ (99.99%) and MnCO ₃ (99.95%). Add 2% raw material mass fraction of Li ₂ CO ₃ (99.99%) as a flux. Place the weighed materials in a mortar, add an appropriate amount of absolute ethanol, mix thoroughly and grind evenly to obtain a mixed material.

(2) Place the mixed material obtained in step (1) into a high-purity alumina crucible, place it in a low-temperature muffle furnace, and pre-sinter at 600°C for 3 hours. After the temperature naturally drops to room temperature, take it out, grind it fully again, put it into a high-temperature tube furnace, and calcine it at 1200°C for 3 hours in a weak reducing atmosphere of 5% H ₂ /95% N ₂ , with a heating rate of 6°C/ min.

(3) After natural cooling to room temperature in the furnace, take out the sintered product, grind and sieve to obtain the target product.

The XRD pattern of the phosphor sample prepared in this example and the excitation spectrum under 630 nm red light monitoring are similar to Example 1. Figure 7 is the emission spectrum of the phosphor prepared in Example 8 of the present invention under the excitation of 365 nm near-ultraviolet light. It can be seen from Figure 7 that the emission spectrum of the phosphor co-doped with Eu ²⁺ and Mn ²⁺ ions contains the characteristic spectra of two luminescence centers, which are located in the blue and red bands respectively. The peak wavelengths of the spectra are located at 455 nm and 630 nm respectively. nm, the synthetic light appears orange-red.

Table 1 shows the CIE chromaticity coordinates and correlated color temperature of the phosphors prepared in Examples 1 to 8 of the present invention. It can be seen that the phosphor prepared in the present invention can emit low color temperature white light under near-ultraviolet light excitation, and the luminescent color of the phosphor can be controlled by adjusting the ion concentration ratio of Eu ²⁺ , Tb ³⁺ , and Mn ²⁺ .

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims (7)

1. A single matrix phosphate fluorescent powder for a white light LED is characterized by comprising the following chemical formula: (SrCa) _{1.98- 2x} La _1-y (PO ₄ ) ₃ O:0.04Eu ²⁺ ,yTb ³⁺ ,4xMn ²⁺ Wherein x is more than or equal to 0 and less than or equal to 0.15, and y is more than or equal to 0 and less than or equal to 0.20; the preparation method comprises the following steps:

(1) Weighing a raw material SrCO according to the metering ratio of the chemical general formula of the fluorescent powder ₃ 、CaCO ₃ 、(NH ₄ ) ₂ HPO ₄ 、La ₂ O ₃ 、Eu ₂ O ₃ 、Tb ₄ O ₇ And MnCO ₃ ；

(2) Adding cosolvent into the above raw materials, placing into a mortar, mixing and grinding uniformly;

(3) Placing the mixed material obtained in the step (2) at 600 ℃ for presintering for 3 hours, naturally cooling to room temperature, taking out, grinding again, calcining for 3 hours at 1200 ℃ in weak reducing atmosphere, and cooling to room temperature along with a furnace;

(4) Grinding and sieving the sintered product obtained in the step (3) to obtain the fluorescent powder;

the cosolvent adopts Li ₂ CO ₃ ；

The addition amount of the cosolvent is 2% of the mass of the raw material.

2. The phosphor of claim 1, wherein x and y cannot be both 0.

3. The phosphor of claim 1, wherein 0.10 x 0.125,0.05 y 0.10.

4. The phosphor of claim 1, wherein x = 0.10,0.05 +.y +.0.10.

5. A method of preparing the phosphor of any one of claims 1-4, comprising the steps of:

(1) According to the fluorescent powderThe raw material SrCO is weighed according to the metering ratio of the chemical general formula ₃ 、CaCO ₃ 、(NH ₄ ) ₂ HPO ₄ 、La ₂ O ₃ 、Eu ₂ O ₃ 、Tb ₄ O ₇ And MnCO ₃ ；

(2) Adding cosolvent into the above raw materials, placing into a mortar, mixing and grinding uniformly;

(3) Placing the mixed material obtained in the step (2) at 600 ℃ for presintering for 3 hours, naturally cooling to room temperature, taking out, grinding again, calcining for 3 hours at 1200 ℃ in weak reducing atmosphere, and cooling to room temperature along with a furnace;

(4) Grinding and sieving the sintered product obtained in the step (3) to obtain the fluorescent powder;

the cosolvent adopts Li ₂ CO ₃ ；

The addition amount of the cosolvent is 2% of the mass of the raw material.

6. The method of claim 5, wherein absolute ethanol is added and mixed and milled uniformly.

7. The process according to claim 5, wherein the weakly reducing atmosphere is at 5 vol.% H ₂ /95vol％N ₂ Is an atmosphere of (2).