CN110981481B - Preparation method of stepped complex-phase fluorescent ceramic for high-luminous-efficiency white light LED - Google Patents
Preparation method of stepped complex-phase fluorescent ceramic for high-luminous-efficiency white light LED Download PDFInfo
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Abstract
Disclosure of the inventionA preparation method of the stepped complex phase fluorescent ceramic for the white light LED with high luminous efficiency is provided, which comprises the following steps: accurately weighing raw material powder, MgO/MgF2And sintering aid ball milling mixing, drying, sieving and calcining, ball milling and mixing the calcined mixed powder and the dispersant, adding the adhesive and the plasticizer, continuing ball milling, and respectively preparing MgO/MgF with different concentrations2Respectively defoaming the mixed slurry, and then carrying out tape casting to obtain the mixed slurry containing MgO/MgF with different concentrations2The cast film of (3); casting the film according to MgO/MgF2Overlapping the content from high to low to obtain a casting sheet, and carrying out cold isostatic pressing on the casting sheet to obtain a ceramic biscuit; and (3) carrying out vacuum sintering, annealing and double-side polishing on the ceramic biscuit blank after the ceramic biscuit blank is subjected to binder removal, thus obtaining the ceramic biscuit. The invention adopts the tape casting method to prepare the ceramic biscuit, is easy to realize the step change that the content of two phases in the ceramic is reduced from bottom to top, and introduces MgO/MgF2As two phases, the utilization rate of blue light can be improved, the fluorescence output light intensity is improved, and the thermal stability of the ceramic can be stabilized.
Description
Technical Field
The invention relates to the technical field of fluorescent ceramics, in particular to a preparation method of a stepped complex phase fluorescent ceramic for a high-luminous-efficiency white light LED.
Background
The white light LED has the advantages of long service life, small volume, low energy consumption, environmental protection, energy conservation and no harmful substances, and is expected to become a new illumination light source of the fourth generation. The most widely used and technically mature white light L at presentThe ED technology is that a gallium nitride-based blue light chip is added with yellow (green) color fluorescent powder (cerium-doped yttrium/lutetium aluminum garnet, Ce: Y3Al5O12/Ce:YLu3Al5O12) The technique forms white light. The GaN layer emits blue light, and the phosphor layer encapsulated by the silicone resin absorbs the blue light and emits yellow (green) light. The unused blue light mixes with the light emitted by the fluorescence conversion material to form white light. However, such LED packages face a problem of poor thermal stability. In addition, the silicone resin is easy to age, which causes light decay and color temperature shift, and reduces the luminous efficiency. Resulting in a reduction in LED lifetime. The transparent fluorescent ceramic is adopted to replace fluorescent powder and silica gel, so that the problems can be effectively solved. The transparent fluorescent ceramic has good thermal conductivity and thermal stability, and can improve brightness and spectral stability. In the field of transparent fluorescent ceramics, patent CN104891967A discloses a preparation method of a green transparent ceramic phosphor for high-luminous-efficiency LEDs. The green light fluorescent transparent ceramic prepared by the method has a simple structure, and the white light LED has high luminous efficiency and quantum efficiency.
In laser applications, it is often desirable to have a transparent ceramic that is fully dense without pores and without the presence of two phases. Two phases within the ceramic can cause severe scattering losses, resulting in a reduction in optical quality. However, in luminescent applications, scattering is one of the important factors affecting the luminescent properties. Optimized scattering centers can not only improve absorption efficiency, but also improve extraction of the portion of the converted light that is trapped by total internal reflection. Therefore, it is very important to produce a certain number of scattering centers for transparent ceramics to improve the luminescent properties of the ceramics. CN106145922A discloses a preparation method of YAG transparent fluorescent ceramic for LED, which is characterized in that a fluorescent ceramic with a certain scattering center is prepared by adding a certain proportion of metal ions and utilizing a high-temperature solid phase method. CN109987932A discloses a complex phase fluorescent ceramic for white light illumination, a preparation method and a light source device, which utilize oxide to disperse light such as Y2O3The problems that the white light of the fluorescent material is not uniform and the thermal shock resistance of the fluorescent material is weak in the current white light laser illumination are effectively solved. However, these methods do not achieve well-controlled distribution of two phases by introducing two phases. Although the utilization of blue light is improved to some extent. However, it is not limited toBecause of the uniform distribution of the two phases, the two phases positioned on the upper part of the ceramic cause fluorescence reflection, so that the fluorescence is not easy to output, and the intensity of the generated fluorescence is reduced. CN107673760A proposes that a pore-forming agent is used for preparing a porous ceramic material with a gradient structure by adopting an extrusion molding and hot pressing method. Although the ceramic having the stepped porosity can be prepared, the introduction of the pores as the scattering center greatly reduces the thermal stability of the ceramic, and the thermal conductivity of the ceramic is greatly reduced due to the introduction of the pores. As a fluorescence conversion device, the thermal conductivity of ceramics is an extremely important index. In addition, the preparation of ceramic films by extrusion molding suffers from the problem of instability. The thickness of the film is difficult to control, the flatness of the film is difficult to unify, and metal impurities are easy to introduce in the extrusion process.
Disclosure of Invention
The invention aims to provide a preparation method of a stepped complex phase fluorescent ceramic for a high-luminous-efficiency white light LED.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows: a preparation method of a stepped complex phase fluorescent ceramic for a high luminous efficiency white light LED adopts a tape casting method, and specifically comprises the following steps:
(1) weighing raw material powder according to the stoichiometric ratio of each element in the chemical formula of the fluorescent ceramic, and weighing MgO/MgF accounting for 0.5-3.2% of the total mass of the raw material powder2(ii) a Using water or absolute ethyl alcohol as ball milling medium, accurately weighing raw material powder, MgO/MgF2Placing the sintering aid ethyl orthosilicate in a ball milling tank, performing ball milling for 14-16 hours to obtain mixed powder, drying the ball-milled powder, sieving the powder, and placing the powder in a muffle furnace for calcining;
(2) mixing and ball-milling the calcined mixed powder and the dispersing agent according to a certain proportion, adding the adhesive and the plasticizer after ball-milling for 0.5-3 h, and continuing ball-milling for 0.5-2 h; respectively preparing MgO/MgF with different concentrations2The mixed slurry of (1);
(3) will contain MgO/MgF in different concentrations2The mixed slurry is respectively defoamed for 30-60 min, and then tape casting is carried out to obtain the mixed slurry containing MgO/MgF with different concentrations2The cast film of (3); casting the film according to MgO/MgF2Overlapping 5-50 layers from high to lowThen obtaining a casting sheet, placing the casting sheet under the pressure of 150-300 Mpa for cold isostatic pressing, and keeping the pressure for 5-10 min to obtain a ceramic biscuit;
(4) and placing the ceramic blank in a muffle furnace for glue removal treatment, then placing the blank in a vacuum furnace for sintering, finally placing the ceramic in the muffle furnace for annealing in air atmosphere and polishing the two sides to obtain the ceramic.
The chemical formula of the fluorescent ceramic is as follows: (A)1-xCex)3B5O12Wherein A is any one or more of Y, Lu, Gd and Tb, B is at least one of Al or Ga, 0<x≤0.01。
Preferably, in the step (1), the ball milling rotating speed is 160-180 r/min; the muffle furnace calcining temperature is 600-1000 ℃, and the heat preservation time is 5-8 h.
Preferably, in the step (2), the rotation speed of the two ball mills is 150-230 r/min.
Preferably, in the step (2), the dispersant is one or more of herring oil, fish oil, oleic acid, Polyetherimide (PEI) or NP-10; the addition amount of the dispersing agent is 2-10% of the total mass of the mixed powder.
Preferably, in step (2), the binder is polyvinyl butyral (PVB); the addition amount of the binder is 3-10% of the total mass of the mixed powder.
Preferably, in the step (2), the plasticizer is Butyl Benzyl Phthalate (BBP) and/or tert-butyl peroxypivalate (BPP); the addition amount of the plasticizer is 2-7% of the total mass of the mixed powder.
Preferably, in the step (3), MgO/MgF is arranged between two adjacent casting films2The content gradient difference is 0.5-2 wt%.
Preferably, in the step (3), the thickness of the casting film sheet is 0.1-1 mm.
Preferably, in the step (4), the glue discharging temperature is 600-900 ℃; the vacuum sintering temperature is 1750-1820 ℃, and the vacuum degree in the furnace chamber is kept at 10-3～10-4Pa; the ceramic annealing temperature is 1200-1600 ℃.
Compared with the prior art, the invention has the following beneficial effects:
(1) compared with the prior fluorescent ceramic body, MgO/MgF is introduced2As two phases, the blue light scattering point in the ceramic body is increased, the utilization rate of blue light is greatly improved, and the thermal stability of the ceramic can be ensured.
(2) Compared with the existing complex phase fluorescent ceramic body, the stepped complex phase ceramic phosphor has the complex phase content increased from bottom to top, and the fluorescent output intensity is improved while the utilization rate of blue light is improved. Under the excitation of blue light with the wavelength of 450nm, the luminous efficiency can reach 220-250 lm/W.
Drawings
Fig. 1 is a schematic structural diagram of a light-emitting device.
Fig. 2 is a schematic view of light propagating in a ceramic. Wherein (a) is a schematic diagram of light propagation in the stepped complex phase LuAG porous fluorescent ceramic; (b) is a schematic diagram of light propagation in common LuAG complex phase fluorescent ceramic.
Detailed Description
The invention is described in further detail below with reference to the figures and specific examples.
Unless otherwise stated, the starting materials used in the following examples are all commercially available products.
Example 1
(1) According to the chemical formula (Lu)0.998Ce0.002)3Al5O12Weighing 60g of lutetium oxide, cerium oxide and aluminum oxide serving as raw materials according to the stoichiometric ratio of the elements; weighing MgO which accounts for 3.0%, 1.5% and 0.5% of the total mass of the raw material powder; using absolute ethyl alcohol as a ball milling medium, placing accurately weighed raw material powder, MgO and 0.33ml of TEOS into a ball milling tank, and ball milling for 14 hours at 180r/min to obtain uniformly mixed slurry; drying and sieving the ball-milled slurry, calcining the dried and sieved slurry in a muffle furnace at the temperature of 600 ℃, and preserving heat for 8 hours;
(2) mixing the calcined powder and herring oil, performing ball milling for 1.5h at the rotating speed of 230r/min, adding PVB and BPP, and performing ball milling for 0.5h at the rotating speed of 230r/min to respectively prepare slurry with the MgO concentration of 3.0 wt%, 1.5 wt% and 0.5 wt%; wherein the addition amount of the herring oil is 1.8g, the addition amount of the PVB is 2.4g, and the addition amount of the BPP is 1.8 g;
(3) removing bubbles from the slurry for 30min respectively, casting to obtain casting membranes with the thickness of 0.1mm, superposing 50 layers of MgO with the addition amounts of 3.0 wt%, 1.5 wt% and 0.5 wt% according to the content of MgO, and keeping the pressure at 300MPa for 5min for cooling to obtain ceramic biscuit;
(4) placing the ceramic biscuit in a muffle furnace for degumming at 600 ℃, then placing the biscuit in a vacuum furnace for sintering at 1800 ℃, wherein the heating rate is 0.5 ℃/min, and the vacuum degree in the furnace chamber is 10-4Pa the ceramic was finally annealed in a muffle furnace at 1200 ℃ and polished to 1mm on both sides.
By adopting the light-emitting device shown in fig. 1, the ceramic two-phase content on the side close to the blue light chip is high, the ceramic two-phase content on the side far away from the blue light chip is low, and the two-phase rate is reduced in a step manner from bottom to top. Blue light is input from the side with high two-phase ratio. As shown schematically in fig. 2 for light propagation in the ceramic, blue light is scattered by two phases encountered in the ceramic, and the fluorescent ceramic improves the utilization of blue light by the ceramic. Compared with common two-phase ceramics, the stepped two-phase distribution can realize high fluorescence output intensity while ensuring high blue light utilization rate, thereby realizing improvement of luminous efficiency. In addition, MgO is introduced as a two-phase, which can stabilize the thermal conductivity of the fluorescent ceramic.
Under the excitation of 450nm blue light, the luminous efficiency of the ceramic can reach 250lm/W, and the thermal conductivity can reach 8W/m.k at room temperature.
Example 2
(1) According to the formula (Y)0.995Ce0.005)3Al5O12Weighing 60g of raw material powder yttrium oxide, cerium oxide and aluminum oxide according to the stoichiometric ratio of each element; weighing MgF accounting for 2.8 percent, 1.6 percent and 1.0 percent of the total mass of the raw material powder2(ii) a Using absolute ethyl alcohol as ball milling medium, accurately weighing raw material powder and MgF20.35ml of TEOS is placed in a ball milling tank to be ball milled for 16h at 170r/min, evenly mixed slurry is obtained, the ball milled slurry is dried, sieved, placed in a muffle furnace to be calcined at 800 ℃, and kept warm for 6 h;
(2) mixing the calcined powder with PEI, ball-milling at 200r/min for 2h, adding PVB and BBP, ball-milling at 200r/min for 1h, and respectively preparingPreparation of MgF2The slurry with the concentration of 2.8 wt%, 1.6 wt% and 1.0 wt%; wherein the addition amount of PEI is 3.0g, the addition amount of PVB is 3.6g of the total mass of the mixed powder, and the addition amount of BBP is 3.0g of the total mass of the mixed powder;
(3) removing bubbles from the slurry for 35min respectively, and carrying out tape casting to obtain tape-casting membranes with the thickness of 0.2 mm; MgF with the addition amounts of 2.8 wt%, 1.6 wt% and 1.0 wt% respectively2According to MgF2Superposing 20 layers from high to low, keeping the pressure at 150Mpa for 10min, cooling to obtain ceramic biscuit;
(4) placing the ceramic blank in a muffle furnace for binder removal at 800 ℃, then placing the blank in a vacuum furnace for sintering at 1760 ℃, wherein the heating rate is 1.0 ℃/min, and the vacuum degree in the furnace chamber is 10-3Pa finally the ceramic was annealed in a muffle furnace at 1600 ℃ and polished to 1.0mm on both sides.
By adopting the light-emitting device shown in fig. 1, the ceramic two-phase content on the side close to the blue light chip is high, the ceramic two-phase content on the side far away from the blue light chip is low, and the two-phase rate is reduced in a step manner from bottom to top. Blue light is input from the side with high two-phase ratio. As shown schematically in fig. 2 for light propagation in the ceramic, blue light is scattered by two phases encountered in the ceramic, and the fluorescent ceramic improves the utilization of blue light by the ceramic. Compared with common two-phase ceramics, the stepped two-phase distribution can realize high fluorescence output intensity while ensuring high blue light utilization rate, thereby realizing improvement of luminous efficiency. Additionally introducing MgF2The two phases stabilize the thermal conductivity of the fluorescent ceramic.
Under the excitation of 450nm blue light, the luminous efficiency of the ceramic can reach 230lm/W, and the thermal conductivity at room temperature can reach 11W/m.k.
Example 3
(1) According to the formula (Y)0.99Ce0.01)3Al5O12Weighing 60g of raw material powder yttrium oxide, cerium oxide and aluminum oxide according to the stoichiometric ratio of each element; weighing MgO which accounts for 3.2 percent, 1.7 percent and 0.7 percent of the total mass of the raw material powder; absolute ethyl alcohol is used as a ball milling medium. Accurately weighed raw material powder, MgO and 0.32ml TEOS are placed in a ball milling tank to be ball milled for 16h at the speed of 150r/min to obtain evenly mixed slurry, and the ball milled slurry isDrying the slurry, sieving, calcining in a muffle furnace at 1000 ℃, and keeping the temperature for 5 hours;
(2) mixing the calcined powder and oleic acid, performing ball milling for 2 hours at the rotating speed of 150r/min, adding PVB and BPP, and performing ball milling for 1 hour at the rotating speed of 150r/min to respectively prepare slurry with the MgO concentration of 3.2 wt%, 1.7 wt% and 0.7 wt%; wherein the addition amount of oleic acid is 4.8g of the total mass of the mixed powder, the addition amount of PVB is 4.8g of the total mass of the mixed powder, and the addition amount of BPP is 3.6g of the total mass of the mixed powder;
(3) removing bubbles from the slurry for 60min respectively, casting to obtain casting membranes with the thickness of 1mm, superposing 5 layers of MgO casting membranes with the addition amounts of 3.2 wt%, 1.7 wt% and 0.7 wt% according to the content of MgO, keeping the pressure at 300MPa for 8min, cooling and the like to obtain ceramic biscuit;
(4) placing the ceramic blank in a muffle furnace for binder removal at 900 ℃, then placing the blank in a vacuum furnace for sintering at 1780 ℃, wherein the heating rate is 1.5 ℃/min, and the vacuum degree in the furnace chamber is 10-3Pa, finally placing the ceramic in a muffle furnace to anneal at 1400 ℃ and polishing the two sides to 2.0 mm.
By adopting the light-emitting device shown in fig. 1, the ceramic two-phase content on the side close to the blue light chip is high, the ceramic two-phase content on the side far away from the blue light chip is low, and the two-phase rate is reduced in a step manner from bottom to top. Blue light is input from the side with high two-phase ratio. As shown schematically in fig. 2 for light propagation in the ceramic, blue light is scattered by two phases encountered in the ceramic, and the fluorescent ceramic improves the utilization of blue light by the ceramic. Compared with common two-phase ceramics, the stepped two-phase distribution can realize high fluorescence output intensity while ensuring high blue light utilization rate, thereby realizing improvement of luminous efficiency. In addition, MgO is introduced as a two-phase, which can stabilize the thermal conductivity of the fluorescent ceramic.
Under the excitation of 450nm blue light, the luminous efficiency of the ceramic can reach 220lm/W, and the thermal conductivity at room temperature can reach 10W/m.k.
Claims (7)
1. A preparation method of a stepped complex phase fluorescent ceramic for a high luminous efficiency white light LED is characterized by adopting a tape casting method and specifically comprising the following steps:
(1) according to the fluorescenceWeighing raw material powder according to the stoichiometric ratio of each element in the chemical formula of the optical ceramic, and weighing MgO/MgF accounting for 0.5-3.2% of the total mass of the raw material powder2(ii) a Using absolute ethyl alcohol as ball milling medium, accurately weighing raw material powder and MgO/MgF2Placing the sintering aid ethyl orthosilicate in a ball milling tank, performing ball milling for 14-16 hours to obtain mixed powder, drying the ball-milled powder, sieving the powder, and placing the powder in a muffle furnace for calcining; the chemical formula of the fluorescent ceramic is as follows: (A)1-xCex)3B5O12Wherein A is any one or more of Y, Lu, Gd and Tb, B is at least one of Al or Ga, 0<x≤0 .01；
(2) Mixing the calcined mixed powder and a dispersing agent in proportion, ball-milling for 0.5-3 h, adding an adhesive and a plasticizer, and continuing ball-milling for 0.5-2 h; respectively preparing MgO/MgF with different concentrations2The mixed slurry of (1);
(3) will contain MgO/MgF in different concentrations2The mixed slurry is subjected to defoaming for 10-60 min respectively, and then tape casting is performed to obtain the mixed slurry containing MgO/MgF with different concentrations2The cast film of (3); casting the film according to MgO/MgF2Superposing 5-50 layers from high to low to obtain a casting sheet, carrying out cold isostatic pressing on the casting sheet under the pressure of 150-300 MPa for molding, and maintaining the pressure for 5-10 min to obtain a ceramic biscuit;
(4) and placing the ceramic blank in a muffle furnace for glue removal treatment, then placing the blank in a vacuum furnace for sintering, finally placing the ceramic in the muffle furnace for annealing in air atmosphere and polishing the two sides to obtain the ceramic.
2. The preparation method of the stepped complex phase fluorescent ceramic for the high luminous efficiency white light LED according to claim 1, wherein in the step (1), the ball milling speed is 160-180 r/min; the muffle furnace calcining temperature is 600-1000 ℃, and the heat preservation time is 5-8 h.
3. The preparation method of the stepped complex phase fluorescent ceramic for the high luminous efficiency white light LED according to claim 1, wherein in the step (2), the rotation speed of the ball milling for two times is 150-230 r/min.
4. The method for preparing the stepped complex phase fluorescent ceramic for the high luminous efficiency white light LED as claimed in claim 1, wherein in the step (2), the binder is polyvinyl butyral; the addition amount of the adhesive is 3-10% of the total mass of the mixed powder.
5. The method for preparing the stepped complex phase fluorescent ceramic for the high luminous efficiency white light LED as claimed in claim 1, wherein in the step (3), MgO/MgF is arranged between two adjacent layers of casting films2The content gradient difference is 0.5-2 wt%.
6. The method for preparing the stepped complex phase fluorescent ceramic for the high luminous efficiency white light LED according to claim 1, wherein in the step (3), the thickness of the casting film is 0.1-1 mm.
7. The method for preparing the stepped complex phase fluorescent ceramic for the high luminous efficiency white light LED according to claim 1, wherein in the step (4), the binder removal temperature is 600-900 ℃; the vacuum sintering temperature is 1750-1820 ℃, and the vacuum degree in the furnace chamber is kept at 10-3～10-4Pa; the ceramic annealing temperature is 1200-1600 ℃.
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| CN201911420311.2A CN110981481B (en) | 2019-12-31 | 2019-12-31 | Preparation method of stepped complex-phase fluorescent ceramic for high-luminous-efficiency white light LED |
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| CN106565219A (en) * | 2016-11-07 | 2017-04-19 | 安徽中威光电材料有限公司 | Magnesium fluoride-doped and fluorescent ceramic base for high-power LED and preparation method for ceramic base |
| CN107540368A (en) * | 2017-02-28 | 2018-01-05 | 江苏罗化新材料有限公司 | The preparation method and LED module of complex phase translucent fluorescent ceramics |
| CN109896851A (en) * | 2017-12-07 | 2019-06-18 | 上海航空电器有限公司 | Ceramic composite, preparation method and light supply apparatus with concentration gradient |
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| CN106565219A (en) * | 2016-11-07 | 2017-04-19 | 安徽中威光电材料有限公司 | Magnesium fluoride-doped and fluorescent ceramic base for high-power LED and preparation method for ceramic base |
| CN107540368A (en) * | 2017-02-28 | 2018-01-05 | 江苏罗化新材料有限公司 | The preparation method and LED module of complex phase translucent fluorescent ceramics |
| CN109896851A (en) * | 2017-12-07 | 2019-06-18 | 上海航空电器有限公司 | Ceramic composite, preparation method and light supply apparatus with concentration gradient |
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