Rare earth luminescent material and preparation method thereof

Abstract

The invention discloses a rare earth luminescent material. The rare earth luminescent material comprises the following components: BaMgAlxOy: Eu < 2 + >, the rare earth luminescent material powder is prepared by grinding europium oxide, barium oxide, magnesium oxide and aluminum oxide, calcining and sintering in a rare earth sintering furnace to prepare a precursor raw material, adding an ammonium chloride fluxing agent, carrying out high-temperature secondary sintering in a nitrogen reducing atmosphere, and naturally cooling to room temperature. The invention also discloses a preparation method of the rare earth luminescent material. The preparation method comprises the following preparation steps in sequence: preparing raw materials, grinding, calcining and sintering, adding a fluxing agent for secondary sintering, and cooling to obtain the rare earth luminescent material. After the rare earth luminescent material is used for preparing an LED plant growth lamp, the flux density of photosynthetic light quantum can be improved, and photosynthesis can be promoted. The mode of firstly preparing the precursor raw material and then carrying out secondary sintering is adopted, so that the primary sintering temperature is lower than 1400 DEG C, and the secondary sintering temperature even can be lower than 1400 DEG C, so that the energy consumption is low.

Description

Technical Field

[0001] The present invention relates to rare earth related keywords, and in particular to a rare earth luminescent material and a preparation method thereof. Background Art

[0002] The rare earth elements in rare earth materials have a unique electronic structure and can emit light. After activation or co-activation, rare earth elements can emit fluorescence in a variety of colors. Rare earth materials are a kind of luminescent materials with relatively stable performance. They are widely used in lighting, imaging, green factories and other fields, and have broad development prospects. The spectrum of near-ultraviolet light, green light and yellow light in the solar spectrum is almost not used by green plants. The absorbed light can be used for biological nitrogen fixation, nutrient absorption and synthesis of green plant vitamins, etc., indirectly promoting the growth of green plants. At present, ordinary plant growth lamps mainly use blue and red monochrome LEDs. However, there are few studies on how to improve the photosynthetic photon flux density.

[0003] In addition, Ye Yan mentioned in the paper "Preparation Method of LED Rare Earth Luminescent Materials for Plant Lighting" published in "Light Sources and Lighting" No. 7, 2022, No. 169 that the disadvantage of preparing LED rare earth luminescent materials by high-temperature solid-phase method is that the sintering temperature is too high, mostly above 1400°C. It consumes a lot of energy. Patent with announcement number CN108456523B: A phosphor for plant growth LED lamps and a preparation method thereof, which uses raw materials mixed and loaded into a crucible, sintered in a high-temperature furnace under a protective atmosphere of 1300-1400°C for 2-4 hours, and then cooled to room temperature to obtain the phosphor for plant growth LED lamps. Patent with publication number CN112625684A: A deep red niobate phosphor for agricultural lighting and its preparation method, the preparation method is: after grinding and mixing raw materials containing barium compounds, lanthanum compounds, niobium compounds and manganese compounds, calcining at 1300-1550℃ for 5-10h, cooling to room temperature with the furnace, the red phosphor can be obtained. The energy consumption is relatively large. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects in the prior art and provide a rare earth luminescent material, which can improve the photosynthetic photon flux density and promote photosynthesis after being prepared into an LED plant growth lamp.

[0005] To achieve the above purpose, the technical solution of the present invention is to design a rare earth luminescent material, the composition of the rare earth luminescent material is: BaMgAlxOy:Eu2+; the rare earth luminescent material powder is made of europium oxide, barium oxide, magnesium oxide and aluminum oxide, and then placed in a rare earth sintering furnace for calcination and sintering to form a precursor raw material, and then ammonium chloride flux is added, and high-temperature secondary sintering is performed in a nitrogen reducing atmosphere, and naturally cooled to room temperature. The present invention adopts a method of first preparing the precursor raw material and then secondary sintering, so the primary sintering temperature is lower than 1400°C, and the secondary sintering can even be lower than 1400°C, so the energy consumption is small. The LED plant growth lamp made of the rare earth luminescent material of the present invention has a high photosynthetic photon flux density and effectively promotes photosynthesis.

[0006] A further technical solution is that x=10, y=17; the mass ratio of europium oxide, barium oxide, magnesium oxide and aluminum oxide is 3.1:2.0:1.4:1.

[0007] The present invention also provides a technical solution, which is a method for preparing a rare earth luminescent material, comprising the following preparation steps performed in sequence: raw material preparation, grinding, calcination and sintering, adding a flux for secondary sintering, and cooling to obtain the rare earth luminescent material.

[0008] A further technical solution is that the sintering process is: grinding and mixing europium oxide, barium oxide, magnesium oxide and aluminum oxide and loading them into the furnace. After loading, sintering begins. The secondary sintering process is: adding flux and then starting sintering. After sintering, the furnace is cooled or naturally cooled to room temperature.

[0009] A further technical solution is that a rare earth sintering furnace is used in the sintering and secondary sintering processes, and the rare earth sintering furnace includes a furnace body, a raw material conveying mechanism connected to the furnace body, and a nitrogen conveying mechanism connected to the furnace body. A plurality of loading and distributing trays are arranged from top to bottom in the furnace body, and a plurality of through holes are arranged at intervals on each loading and distributing tray, and the through holes on adjacent loading and distributing trays are arranged in a staggered manner. Since a plurality of loading and distributing trays are arranged from top to bottom in the furnace body, and through holes are arranged on the trays, after feeding into the furnace body through the raw material conveying mechanism, the setting of the loading and distributing trays can play a role in distributing materials, and a part of the raw materials is retained on each tray, and some of the raw materials fall to the loading and distributing trays on the lower layer through the through holes, so as to distribute the raw materials as evenly as possible during the furnace loading process.

[0010] A further technical solution is that a column is arranged in the furnace body, the column is fixedly connected to the inner bottom wall or the inner top wall of the furnace body and is located at the center of the furnace body, and a loading and distributing plate is sleeved on the column, each loading and distributing plate is arranged to be inclined with respect to the horizontal plane, and the inclination directions of adjacent loading and distributing plates are opposite; the upper end of the highest loading and distributing plate in the furnace body is directly opposite to the feeding pipe of the raw material conveying mechanism. The raw material stays on the loading and distributing plate by the friction between the raw material and the loading and distributing plate, and the two adjacent loading and distributing plates have opposite inclination directions, and the material that falls from the lower end of the loading and distributing plate due to the inclination can also fall into the next layer, so as to distribute the material more evenly.

[0011] A further technical solution is that the raw material conveying mechanism includes a raw material tank and a pneumatic conveying pump connected to the raw material tank, and the feeding pipe on the pneumatic conveying pump is connected to the top of the furnace body; the nitrogen conveying mechanism includes a nitrogen storage tank, and the nitrogen storage tank is connected to the furnace body through a conveying pipe, and the conveying pipe is provided with an air pump, a pressure gauge and an air valve.

[0012] The advantages and beneficial effects of the present invention are: the present invention adopts the method of first preparing the precursor raw material and then performing secondary sintering, so the primary sintering temperature is lower than 1400°C, and the secondary sintering can even be lower than 1400°C, so the energy consumption is small. The LED plant growth lamp made of the rare earth luminescent material of the present invention has a high photosynthetic photon flux density and effectively promotes photosynthesis.

[0013] Since multiple loading and distributing trays are arranged from top to bottom in the furnace body, and through holes are arranged on the trays, after the raw material is fed into the furnace body through the raw material conveying mechanism, the loading and distributing trays can be used to distribute the materials. A part of the raw materials is retained on each tray, and some of the raw materials fall onto the loading and distributing trays on the lower layer through the through holes, so that the raw materials are distributed as evenly as possible during the loading process.

[0014] The raw materials stay on the loading and distributing trays by the friction between them. The two adjacent loading and distributing trays are tilted in opposite directions, and the materials that fall from the lower end of the loading and distributing trays due to the tilt can also fall into the next layer, so as to distribute the materials more evenly. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of a rare earth sintering furnace for preparing a rare earth luminescent material in Example 1 of the present invention; Figure 2 yes Figure 1 Rear view of Figure 3 yes Figure 1 Left view of Figure 4 yes Figure 3 Middle AA section view; Figure 5 yes Figure 1 Schematic diagram of the top view after rotating 180°; Figure 6 yes Figure 4 A partial enlarged schematic diagram of the left end portion of ; Figure 7 yes Figure 6 A top view of the two material loading and distributing trays being taken down from the uprights and laid out side by side on the ground; Figure 8 is a schematic diagram of a rare earth sintering furnace according to a second embodiment of the present invention; Fig. 9 yes Figure 8 An enlarged schematic diagram of the middle-load material distribution plate and connecting rod; Fig.10 yes Fig. 9 A top view of an exploded schematic diagram of a material loading and distributing plate and a connecting rod; Fig.11 is a schematic diagram of a rare earth sintering furnace according to Embodiment 3 of the present invention; Fig.12 yes Fig.11 A partial enlarged schematic diagram of the middle-load material distribution tray and its surrounding components; Fig.13 yes Fig.12 A top view of an exploded schematic diagram of the middle loading material distribution plate and the connecting rod; Fig.14 is a schematic diagram of a rare earth sintering furnace according to a fourth embodiment of the present invention; Fig.15 yes Fig.14 An enlarged schematic diagram of the feeding pipe and the annular metal mesh; Fig.16 yes Fig.15 A partial enlarged schematic diagram of the lower end portion of ; Fig.17 yes Fig.15 Top view after removing the feed tube; Fig.18 yes Fig.17 A schematic diagram showing a disc-shaped metal mesh but without the material carrier and distributor tray; Fig.19 yes Fig.18 A schematic diagram showing the back of the limit plate; Fig. 20 yes Fig.17 Schematic diagram of the decomposition of the annular metal mesh, disc metal mesh and limiting plate.

[0016] In the figure: 1. furnace body; 2. raw material conveying mechanism; 3. nitrogen conveying mechanism; 4. material loading and distributing plate; 5. through hole; 6. column; 7. feed pipe; 8. curved plate; 9. raw material tank; 10. nitrogen storage tank; 11. conveying pipe; 12. pressure gauge; 13. through hole; 14. connecting rod; 15. spring; 16. opening; 17 opening; 18. annular metal mesh; 19. step ring; 20. disc-shaped metal mesh; 21. limit plate. DETAILED DESCRIPTION

[0017] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and embodiments. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0018] Embodiment 1: Figures 1 to 7 As shown (for ease of illustration, Figure 4 Only two loading and distributing trays are shown; Figure 7 The invention relates to a rare earth luminescent material, the composition of which is: BaMgAl x O y :Eu 2+ ; The rare earth luminescent material powder is made of europium oxide Eu2O3, barium oxide BaO, magnesium oxide MgO and aluminum oxide Al2O3, which are ground and calcined in a rare earth sintering furnace to make a precursor raw material, and then ammonium chloride NH4Cl flux is added, and secondary sintering is performed at high temperature in a nitrogen reducing atmosphere, and naturally cooled to room temperature; x=10, y=17; the mass ratio of europium oxide, barium oxide, magnesium oxide and aluminum oxide is 3.1:2.0:1.4:1; in the calcination and sintering process, the sintering temperature is 1300°C, the sintering time is 3h, the secondary sintering temperature is 1250-1450°C, and the time is 2h; the amount of ammonium chloride added is 2% of the mass ratio of the precursor raw material; the grinding time is 1h; The method for preparing the rare earth luminescent material comprises the following preparation steps in sequence: raw material preparation, grinding, calcination and sintering, adding flux for secondary sintering, and cooling to obtain the rare earth luminescent material. The sintering process is: europium oxide, barium oxide, magnesium oxide and aluminum oxide are ground, mixed and then loaded into a furnace, and after loading, sintering begins. The secondary sintering process is: sintering begins after adding flux, and after sintering, the furnace is cooled or naturally cooled to room temperature. The screened raw materials are mixed. During the mixing process, an appropriate amount of water or other solvents are generally added to fully wet and evenly mix the raw materials. After the mixing is completed, the mixture is generally made into particles with a certain particle size and strength by a granulator to prepare for subsequent furnace loading and sintering. During the sintering process, parameters such as the temperature, atmosphere and pressure in the furnace must be strictly controlled to ensure that the rare earth elements can fully react and crystallize. The rare earth products taken out may generally require subsequent processing, such as crushing, screening, magnetic separation, etc., to remove impurities and unreacted raw materials. After these processing steps, rare earth products that meet the requirements are finally obtained.

[0019] A rare earth sintering furnace is used for the sintering and secondary sintering processes. The rare earth sintering furnace includes a furnace body 1, a raw material conveying mechanism 2 connected to the furnace body 1, and a nitrogen conveying mechanism 3 connected to the furnace body 1. A plurality of loading and distributing trays 4 are arranged from top to bottom in the furnace body. A plurality of through holes 5 arranged at intervals are arranged on each loading and distributing tray 4, and the through holes 5 on adjacent loading and distributing trays are staggered.

[0020] A column 6 is arranged in the furnace body 1, and the column 6 is fixedly connected to the inner bottom wall of the furnace body and is located at the center of the furnace body. A loading and distributing plate 4 is sleeved on the column, and each loading and distributing plate is arranged obliquely with respect to the horizontal plane, and the inclination directions of adjacent loading and distributing plates are opposite; the upper end of the highest loading and distributing plate in the furnace body 1 is directly opposite to the feeding pipe 7 of the raw material conveying mechanism 2 (in this scheme, the loading and distributing plate 4 is fixedly sleeved on the column 6; an upwardly tilted curved plate 8 can also be integrally or fixedly arranged on the upper surface of the loading and distributing plate to retain more raw materials, so as to avoid the situation where a small amount of raw materials remain on the loading and distributing plate only by the friction between the raw materials and the loading and distributing plate); The raw material conveying mechanism 2 includes a raw material tank 9 and a pneumatic conveying pump connected to the raw material tank, and a feeding pipe 7 on the pneumatic conveying pump is connected to the top of the furnace body; the nitrogen conveying mechanism 3 includes a nitrogen storage tank 10, and the nitrogen storage tank is connected to the furnace body through a conveying pipe 11, and an air pump, a pressure gauge 12 and an air valve are provided on the conveying pipe 11.

[0021] Embodiment 2: The difference from Embodiment 1 is that Figures 8 to 10As shown, the loading and distributing tray 4 is sleeved on the column 6 and a through hole 13 whose size is larger than the column 6 is set in the middle part of the loading and distributing tray (after such arrangement, the loading and distributing tray 4 has almost no connection with the column 6, and the loading and distributing tray 4 can move relative to the column 6, and is connected to the connecting rod through the spring under the loading and distributing tray 4; this facilitates the tilting of the loading and distributing tray 4, and the column will not interfere with its tilting), a connecting rod 14 fixedly connected to the column is set under the loading and distributing tray, and a spring 15 is fixedly connected to each end of the connecting rod 14, and the end of the spring 15 away from the connecting rod is fixedly connected to the lower surface of the loading and distributing tray, and the free lengths of the two springs 15 are different; a spring with a longer free length is set at the lower part of the end of the feeding pipe 7 of the raw material conveying mechanism of the highest loading and distributing tray 4 in the furnace body 1. In this embodiment, the upwardly tilted curved plate integrally or fixedly arranged on the upper surface of the loading and distributing tray of the previous embodiment can still be retained to retain more raw materials, so as to avoid the situation where a small amount of raw materials remain on the loading and distributing tray due to the friction between the raw materials and the loading and distributing tray; a plurality of spaced through holes 5 are arranged on each loading and distributing tray 4, and the through holes 5 on adjacent loading and distributing trays are staggered. When the raw material conveying mechanism conveys materials into the furnace body 1 (using pneumatic conveying), since the loading and distributing disc is inclined and has through holes on it, part of the material remains on the loading and distributing disc, and part of the material falls into the loading and distributing disc of the next layer, which plays a role in distributing the material. When there is too much material on the loading and distributing disc of the uppermost layer and the spring is compressed, the loading and distributing disc is inclined, which intensifies the distribution of the material on the uppermost layer of the loading and distributing disc to the loading and distributing disc of the lower layer. The two adjacent loading and distributing discs are inclined in opposite directions, and the material that falls from the lower end of the loading and distributing disc due to the inclination can also fall into the next layer. Due to the setting of each layer of curved plates and the effect of friction, each layer can retain part of the material that falls from the through holes and the lower end of the loading and distributing disc of the upper layer. In the process of continuous feeding, the loading and distributing disc of the uppermost layer reaches a dynamic state under the impact of the falling material, the elastic force of the spring and the pressure of the retained material. Dynamic balance, when tilted, the retained material decreases, and after the reduction, it returns to the tilt angle of dynamic balance due to the spring force. The loading and distributing trays of each layer below the top layer also reach their own dynamic balance due to the combined effect of the material falling from the through holes of the upper layer, the sliding down of the lower end of the upper layer, and the material falling from the lower end after the upper layer tilts. Therefore, the design of this structure allows feeding from one place (that is, one feeding pipe is set), but also realizes the uniform distribution of the material loaded in the furnace (the only trouble is that it is necessary to simulate the feeding situation and calculate the amount of raw materials carried by the furnace body before work starts, to avoid the situation where more material falls on the bottom wall of the furnace body due to the material exceeding the carrying capacity of the furnace body); in order to prevent the material falling from the lower end of the loading and distributing tray from falling directly to the bottom wall of the furnace body, a completely inward guide plate can be set on the side wall of the furnace body, so that the material falling from the lower end of the loading and distributing tray falls on the loading and distributing tray of the next layer.

[0022] Embodiment 3: The difference from Embodiment 2 is that Figures 11 to 13 As shown (for ease of illustration, Fig.12 The through holes and through holes are not shown), the material loading and distributing plate 4 is also provided with a plurality of openings 16, the size of the openings 16 is smaller than the average particle size of the raw materials, and the conveying pipe 11 is connected to the bottom of the furnace body 1; the connecting rod 14 is provided with a plurality of evenly distributed openings 17; A more preferred solution is: the spring 15 with a longer free length is harder (i.e., has a larger stiffness coefficient or rigidity), and the spring with a shorter free length is softer, so that after being stressed, the loading and distributing disc will have a larger inclination angle with the horizontal plane, i.e., it will be further inclined toward the lower end, so that it is convenient to distribute a part of the material to the loading and distributing disc of the next layer by inclination. Alternatively, the harder spring can be replaced with a solid cylinder, so that when there is too much raw material on the loading and distributing disc, the spring will be further inclined due to compression and contraction. The spring can be a ceramic spring.

[0023] Principle and effect: This setting of the post-loading process can ensure the uniform distribution of raw materials, avoiding the situation of partial over-density or over-looseness. When there is too much raw material, the spring is compressed and the loading and distributing plate is further tilted, causing part of the raw materials in this layer to fall into the lower layer. In the prior art, during the process of charging the raw materials, attention is paid to the uniform distribution of the raw material particles to avoid the situation of local over-dense or over-loose. Even mixing can ensure the uniform mixing of the reactants, reduce the formation of large particles, and help to obtain finer powders. However, how to ensure that the raw materials in the reaction are still evenly distributed during the reaction in the sintering furnace is rarely paid attention to in the prior art. This embodiment adopts the protective gas to transport from bottom to top, so that the raw materials rise and fall between two adjacent layers; this scheme obtains a more uniform particle size distribution by adjusting the atmosphere; in addition to maintaining the uniform distribution of the raw materials when charging the furnace, the atmosphere is used during sintering to keep the moving raw material flow such as the rising raw material flow and the descending raw material flow uniformly distributed (combined with the principle of the previous embodiment, this embodiment is also evenly distributed when charging the furnace, and the nitrogen protective gas can make the materials in the reaction evenly distributed after the introduction); and optimizing the mixing uniformity to ensure the uniform mixing of the reactants can reduce the formation of large particles, help to obtain finer powders, and also solve the disadvantages of the high-temperature solid phase preparation method that the powder particle size is not small enough and agglomeration is easy to occur.

[0024] Embodiment 4: The difference from Embodiment 3 is that Figures 14 to 20 As shown (for ease of illustration, Fig.17 The disc-shaped metal mesh and the limiting plate are not shown; Figures 18 to 20The mesh holes on the disc-shaped metal mesh are not shown), the column 6 is fixedly connected to the top wall of the furnace body 1; an annular metal mesh 18 is provided in the furnace body, and a step ring 19 is fixed at the bottom of the annular metal mesh 18 or is integrally provided, and the step ring 19 is fixedly connected to the bottom wall of the furnace body by bolts, and the diameter of the annular metal mesh 18 is larger than the diameter of the loading and distributing plate 4, and the annular metal mesh 18 is equidistantly provided with disc-shaped metal meshes 20 in the same number as the loading and distributing plates in the height direction, and the disc-shaped metal mesh is hinged on the annular metal mesh, and a limit block is provided on the hinge at the hinge (so that the disc-shaped metal mesh is not moved due to its own weight or Since the raw material feed is under pressure and can only tilt downward at a certain angle, and there is a gap between the lowest end of the disc-shaped metal mesh at the extreme position and the limit plate 21), the bottom end of the annular metal mesh 18 is fixedly connected to the bottom wall of the furnace body, the bottom wall of the furnace body and the furnace body 1 are separately arranged, and the bottom wall of the furnace body is fixedly connected to the furnace body (such as a flange sealing connection), and a limit plate 21 is also arranged on the annular metal mesh to prevent the disc-shaped metal mesh from flipping upward. The sum of the length of the limit plate and the diameter of the disc-shaped metal mesh is greater than the diameter of the annular metal mesh, and the mesh size of the disc-shaped metal mesh and the annular metal mesh is smaller than the average particle size of the raw material.

[0025] During the cooling process, a certain cooling speed must be maintained to avoid crystal cracking or performance degradation caused by rapid cooling. After cooling to a safe temperature, the furnace door is opened to take out the sintered rare earth product. The prior art basically uses natural cooling or cooling by introducing cold air (such as the prior art patent with publication number CN2489287Y). This method is prone to uneven cooling (the material near the gas inlet is cooled first, and the material far from the gas inlet is cooled later). In addition, after cooling, it is necessary to wait for a while before opening the furnace door (the powder is raised when the cooling gas is introduced. In order to avoid dust formation and waste of sintered rare earth material powder when opening the furnace door, it is necessary to wait quietly for a while; if it is natural cooling, the working hours are too long), and the working hours are greatly extended. Compared with the existing method of cooling rare earth materials by exchanging heat with cooling gas, this embodiment does not generate dust after cooling, and even settles the dust during sintering (that is, this embodiment can continue to use the bottom-up input method of nitrogen protective gas in the previous embodiment, that is, this embodiment can continue to use the method of ensuring that the raw materials during sintering are also evenly distributed in the previous embodiment) while cooling and opening the furnace, which is equivalent to adding a sedimentation process to the cooling process. There is no need to wait after cooling, and the furnace door can be opened directly without generating dust, thereby avoiding the waste of sintered rare earth materials and greatly reducing the cooling time. Compared with natural cooling, the cooling working time is greatly shortened.

[0026] Ceramic torsion springs (capable of withstanding temperatures of 1400°C) may also be provided at the hinges (of the disc-shaped metal mesh and the annular metal mesh). In this way, once the feeding is completed, the disc-shaped metal mesh will flip upwards due to the action of the torsion springs, and the disc-shaped metal mesh and the annular metal mesh will form a basically "closed" space due to the action of the limiting plate (of course, since they are disc-shaped metal mesh and annular metal mesh, they are not actually closed spaces. The "closed" here refers to the raw materials. Since the mesh size of the disc-shaped metal mesh and the annular metal mesh is smaller than the average particle size of the raw materials, the raw materials are basically unable to leave the space formed by each disc-shaped metal mesh and the nearby annular metal mesh).

[0027] After the raw materials are fed into the furnace body through the feeding pipe 7, the pipe mouth of the feeding pipe 7 located in the furnace body 1 is directly opposite to the end of the disc-shaped metal mesh away from the hinge. In this way, although the particle size of the raw materials is larger than the mesh of the disc-shaped metal mesh, the disc-shaped metal mesh is tilted downward, so the raw materials gradually fall into the highest loading and distributing plate 4, and a part of them will fall from the loading and distributing plate to the loading and distributing plate of the lower layer (of course, they will first fall into the disc-shaped metal mesh above the loading and distributing plate of the lower layer); as for the role of the spring and other settings, it is the same as the previous embodiment and will not be repeated here. The protective gas is transported from bottom to top, so that the raw materials rise and fall between two adjacent layers, and the raw materials in the space formed by the disc-shaped metal mesh and the annular metal mesh near it are basically in this space, and less of them "escape" from this space upward through the gap between the disc-shaped metal mesh and the limit plate. At the end of sintering, first open the bottom wall of the furnace body (loosen the bolts on the sealing flange) and pull it downwards, so that the disc-shaped metal mesh is finally pressed onto the loading and distributing plate, and the raw materials in the space formed by the disc-shaped metal mesh and the annular metal mesh nearby are basically pressed onto the loading and distributing plate (because the particle size of the raw materials is larger than the mesh size of the disc-shaped metal mesh and the annular metal mesh), and then loosen the bolts to disconnect the bottom wall of the furnace body from the annular metal mesh, and then open the furnace door (the furnace door of this embodiment is different from the conventional method of setting it on the side of the furnace body. The furnace door is set at the top of this embodiment, and the furnace door can be opened upwards. The feed pipe 7 is located in the furnace body 1 after passing through the furnace door), and then pull the annular metal mesh upwards (or directly pull the top disc-shaped metal mesh) to make the annular metal mesh separate from the bottom of the furnace, and then take out the rare earth luminescent material powder formed by sintering. (In addition, the disc-shaped metal mesh can be replaced with a solid metal mesh, and only one vent is set on the metal mesh near the hinge to facilitate the protective gas to fill the entire furnace body. After this arrangement, if a very thin solid metal mesh is used, the protective gas can even blow the metal mesh hinged on the annular metal mesh upward and tilt it when it is transported from bottom to top. This makes the space formed by the disc-shaped metal mesh and the annular metal meshes nearby more "closed". During sintering, after the protective gas is introduced, a smaller amount of raw materials will "escape" from the gap between the disc-shaped metal mesh and the limiting plate to the outside of the space formed by the disc-shaped metal mesh and the annular metal meshes nearby. In addition, a more preferred solution for the limiting plate is a contoured arc plate, which can better "close" the space formed by the disc-shaped metal mesh and the annular metal meshes nearby).

[0028] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A rare earth luminescent material, characterized in that: The composition of the rare earth luminescent material is: BaMgAl x O y :Eu 2+ The rare earth luminescent material powder is prepared by grinding europium oxide, barium oxide, magnesium oxide and aluminum oxide, calcining and sintering them in a rare earth sintering furnace to make a precursor raw material, adding ammonium chloride flux, sintering at high temperature for the second time in a nitrogen reducing atmosphere, and naturally cooling to room temperature.

2. A rare earth luminescent material according to claim 1, characterized in that: x=10, y=17; the mass ratio of europium oxide, barium oxide, magnesium oxide and aluminum oxide is 3.1:2.0:1.4:

1.

3. A method for preparing the rare earth luminescent material according to claim 1 or 2, characterized in that: The method comprises the following preparation steps which are carried out in sequence: raw material preparation, grinding, calcination and sintering, adding flux for secondary sintering, and obtaining the rare earth luminescent material after cooling.

4. The method for preparing a rare earth luminescent material according to claim 3, characterized in that: The sintering process is: grind and mix europium oxide, barium oxide, magnesium oxide and aluminum oxide and load them into the furnace. After loading, start sintering. The secondary sintering process is: add flux and start sintering. After sintering, cool the furnace or cool it naturally to room temperature.

5. The method for preparing a rare earth luminescent material according to claim 4, characterized in that: A rare earth sintering furnace is used for the sintering and secondary sintering processes. The rare earth sintering furnace includes a furnace body, a raw material conveying mechanism connected to the furnace body, and a nitrogen conveying mechanism connected to the furnace body. A plurality of loading and distributing trays are arranged from top to bottom in the furnace body. A plurality of through holes are arranged at intervals on each loading and distributing tray, and the through holes on adjacent loading and distributing trays are staggered.

6. The method for preparing a rare earth luminescent material according to claim 5, characterized in that: A column is arranged in the furnace body, which is fixedly connected to the inner bottom wall or the inner top wall of the furnace body and is located at the center of the furnace body. A loading and distributing plate is sleeved on the column. Each loading and distributing plate is inclined with respect to the horizontal plane and the inclination directions of adjacent loading and distributing plates are opposite. The highest end of the highest loading and distributing plate in the furnace body is facing the feeding pipe of the raw material conveying mechanism.

7. The method for preparing a rare earth luminescent material according to claim 6, characterized in that: The raw material conveying mechanism includes a raw material tank and a pneumatic conveying pump connected to the raw material tank, and the feeding pipe on the pneumatic conveying pump is connected to the top of the furnace body; the nitrogen conveying mechanism includes a nitrogen storage tank, and the nitrogen storage tank is connected to the furnace body through a conveying pipe, and an air pump, a pressure gauge and an air valve are arranged on the conveying pipe.

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