CN117625175A - Core-shell structured fluorescent powder and preparation method and application thereof - Google Patents

Abstract

The invention discloses a core-shell structure fluorescent powder, a preparation method and application thereof, wherein the fluorescent powder comprises a fluorescent powder with a chemical formula (Re) _1‑x Ce _x ) ₃ Al ₅ O ₁₂ And a shell surrounding the core, wherein the shell has a chemical formula (A) _1‑y Ce _y ) ₃ (Al _1‑z B _z ) ₅ O ₁₂ . The preparation method comprises the following steps: preparing precursor solution by adopting a coprecipitation method, and forming a core-shell structure by adopting the coprecipitation methodFluorescent powder; and mixing the core-shell structure fluorescent powder with glass powder, pouring the mixture into a red copper mold, uniformly stirring the mixture, sintering the mixture in a muffle furnace, and cutting and polishing the sintered material to obtain the reflective fluorescent device, wherein the reflective fluorescent device comprises a light-emitting layer and a red copper sheet which are in an upper-lower position relationship. The method has simple preparation process, and the prepared core-shell structure fluorescent powder is micron-sized and has high purity, so that the uniformity of a luminous center can be maintained; the fluorescent material is applied to preparing a reflective fluorescent device, and the prepared fluorescent device can have high apparent finger.

Description

A core-shell structure phosphor and its preparation method and application

Technical field

The invention relates to the field of fluorescent materials for laser lighting, and in particular to a core-shell structure phosphor and its preparation method and application.

Background technique

Phosphor is a luminescent material that emits photons under high-energy excitation. Among them, inorganic phosphors play an important intermediary role in synthetic spectrum, display, LED/LD lighting, etc. In particular, white light lighting is one of the most important application fields of inorganic phosphors. Generally, white light can be achieved by two methods: the first is based on LED/LD plus phosphor. In addition to using single- and two-color phosphors, doping multiple activators in a single matrix is another method to achieve white light in phosphors. Considering the spatial distance between luminescence centers (or units), multi-activator co-doping in a single matrix can achieve the best spectral uniformity.

Among fluorescent conversion materials, YAG materials have become attractive luminescent host materials due to their excellent chemical and physical properties. YAG matrix has the advantages of physical and chemical stability and transparency, and is one of the most widely studied luminescent materials. At the same time, luminescent materials based on YAG always exhibit excellent optical properties. The urea precipitation method is an important method for preparing inorganic particles with clear morphology and composition. The thermal decomposition of urea in aqueous solution yields a stable pH value, which provides good prospects for precise composition control of ultrafine powders.

CN111087235B discloses a method for preparing YAG transparent ceramics using yttrium/agent/aluminum triple core-shell structure powder. This solution also uses a co-precipitation method to prepare a precursor solution, and then uses a co-precipitation method to form a core-shell structure. The YAG ceramics prepared have good optical quality. Although the co-precipitation method has been applied in the study of nanoparticle synthesis, it has been less used in the preparation of micron-sized particles. It is reported in the literature (Matthias Muller et al., Luminescence and energy transfer of co-doped Sr ₅ MgLa ₂ (BO ₃ ) ₆ : Ce ³⁺ ,Mn ²⁺ , RSC Advances) that the spectrum of this matrix shows that Ce ³⁺ and Mn There is an exchange interaction mechanism between ²⁺ , and its luminescence thermal quenching is mainly caused by Mn ²⁺ ions. This shows that when co-doping multiple activators in a single matrix, the activator concentration is strictly limited due to luminescence quenching. Therefore, the optimization of the concentration and luminescence efficiency of multiple activators in the matrix crystal structure is also a challenging research task.

Contents of the invention

The purpose of the present invention is to provide a core-shell structure phosphor and its preparation method and application. The method has a simple preparation process. The prepared core-shell structure phosphor is micron-level and has high purity, and can maintain the uniformity of the luminescence center; By applying it to the preparation of reflective fluorescent devices, the prepared fluorescent devices can have high rendering index.

In order to achieve the above object, the technical solution adopted by the present invention is: a core-shell structure phosphor. The phosphor includes a core and a shell wrapped around the core. The chemical formula of the core is (Re _1-x Ce _x ) ₃ Al ₅ O ₁₂ , in the formula, Re is Y or Lu, x is the molar percentage of Ce ³⁺ substituted by Y ³⁺ or Lu ³⁺ , 0.0005≤x≤0.005; the chemical formula of the shell is (A _1-y Ce _y ) ₃ (Al _1-z B _z ) ₅ O ₁₂ , in the formula, A is Y or Lu, B is Mn or Cr, y is the mole of Y ³⁺ or Lu ³⁺ replacing Ce ³⁺ position Percentage, 0.001≤y≤0.01, z is the molar percentage of Al ³⁺ replaced by Mn ²⁺ or Cr ³⁺ , 0.001≤z≤0.02.

Preferably, the particle size of the core body is 2-3 μm, and the thickness of the shell is 2-6 μm.

The invention also provides a method for preparing the above-mentioned core-shell structure phosphor. The specific steps are as follows:

(1) Using Y ₂ O ₃ /Lu ₂ O ₃ , Ce ₂ O ₃ and Al ₂ O ₃ as raw material powders, according to the stoichiometric ratio of the corresponding elements in the chemical formula (Re _1-x Ce _x ) ₃ Al ₅ O ₁₂ Weigh each raw material, where x is the mole percentage of Ce ³⁺ substituted by Y ³⁺ or Lu ³⁺ , 0.0005≤x≤0.005; dissolve the above raw materials in nitric acid to form (Re _1-x Ce _x ) ₃ Al ₅ O ₁₂ precursor solution;

(2) After the precursor solution of (Re _1-x Ce _x ) ₃ Al ₅ O ₁₂ is dispersed by ultrasonic waves, add the precipitant urea, stir evenly and let it stand for aging to precipitate (Re _1-x Ce _x ) ₃ Al ₅ O ₁₂ nuclear body precursor;

(3) Using Y ₂ O ₃ /Lu ₂ O ₃ , MnCO ₃ /Cr ₂ O ₃ , Ce ₂ O ₃ and Al ₂ O ₃ as raw material powders, according to the chemical formula (A _1-y Ce _y ) ₃ (Al _{1 - z} B _z ) ₅ The stoichiometric ratio of the corresponding elements in O ₁₂ Weigh each raw material, where y is the mole percentage of Y ³⁺ or Lu ³⁺ replacing Ce ³⁺ position, z is Mn ²⁺ or Cr ³⁺ replacing Al The mole percentage of the ³⁺ position, 0.001≤y≤0.01, 0.001≤z≤0.02; dissolve the above raw materials in nitric acid to form (A _1-y Ce _y ) ₃ (Al _1-z B _z ) ₅ O ₁₂ precursor body solution;

(4) Mix the (A _1-y Ce _y ) ₃ (Al _1-z B _z ) ₅ O ₁₂ precursor solution and the ammonium bicarbonate mixture as the precipitant into the solution obtained in step (2) in drop form. into the mixed solution, stir evenly, collect by filtration, wash with deionized water to remove impurities, and dry at constant temperature to obtain (Re _1-x Ce _x ) ₃ Al ₅ O ₁₂ @(A _1-y Ce _y ) ₃ (Al _1-z B _z ) ₅ O ₁₂ core-shell structure phosphor.

Preferably, in step (2), the added amount of the precipitating agent urea is 0.3-2 mol/L.

Preferably, in step (4), the ammonium bicarbonate mixed solution is prepared from ammonia water and ammonium bicarbonate solution with a molar ratio of 1: (1.4-3), in which the mass fraction of ammonia water is 25-28%, and the carbonic acid content is 25-28%. The molar concentration of the ammonium hydrogen solution is 0.5-1.5 mol/L; the temperature of the constant temperature drying is 55-75°C, and the time is 12-24 hours.

The present invention also provides the application of the above-mentioned core-shell structure phosphor in preparing reflective fluorescent devices. The specific application process is as follows: mix the above-mentioned core-shell structure phosphor with glass powder and then pour it into a copper mold, stir evenly and then place it in the muffle. The material is sintered in a furnace, and the sintered material is cut and polished to obtain a reflective fluorescent device. The reflective fluorescent device includes a luminescent layer and a copper sheet in an upper and lower position.

Preferably, the sieve mesh number of the glass powder is 300-500 mesh, and the mass ratio between the core-shell structure phosphor and the glass powder is (5-10):1.

Preferably, the sintering temperature is 400-1000°C, the sintering time is 1-3 hours, and the thickness of the luminescent layer is 0.1-0.8 mm.

Compared with existing technical solutions, the present invention has the following advantages:

(1) The present invention adopts the core-shell structure powder prepared by the precipitation method. The preparation process is simple, and the prepared core-shell structure fluorescent powder has uniform components and high powder purity; in addition, as a core-shell structure with a size of micron level powder, whose core-shell separation can maintain the uniformity of the luminescent center while avoiding the interaction of co-doped luminescent centers in similar structures;

(2) The present invention can easily realize individual adjustment of each component of the core-shell structure by changing the size, scale and concentration of the luminescent center; this method can provide a new way for phosphor synthesis and spectral integration;

(3) The present invention proposes a luminescent material sintered on a copper substrate, which is used to fix the sample by introducing a small amount of glass powder; the heat generated by the luminescent material can be dissipated through the copper, which is beneficial to improving the thermal shock resistance of the material. (Able to achieve 25W/mm ² ) and thermal conductivity (close to 20Wm ^-1 K ^-1 );

(4) The core-shell structure phosphor prepared by the present invention is used in the preparation of fluorescent devices. When excited by a 25W/ ^mm2 laser, the maximum luminous efficiency of the fluorescent device is 180~240lm/W, the color temperature is 3500~4500K, and the color rendering The index is 90~98, the yield is high, and it is suitable for mass production.

Description of drawings

Figure 1 is a schematic diagram of the structure and luminescence of the core-shell structure phosphor of the present invention;

In Figure 1: 1. Core body, 2. Shell;

Figure 2 is a schematic diagram of the structure and operation of a fluorescent device prepared by using the core-shell structure phosphor of the present invention to prepare a reflective fluorescent device;

In Figure 2: 1. Luminous layer, 2. Copper sheet;

Figure 3 is a graph showing changes in luminous efficiency and CRI of the fluorescent device prepared in Example 3 of the present invention under 450 nm laser excitation.

Detailed ways

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

Example 1

A core-shell structure phosphor. The structure is shown in Figure 1. The phosphor includes a core body and a shell wrapped around the core body. The chemical formula of the core body is (Y _0.9995 Ce _0.0005 ) ₃ Al ₅ O ₁₂ ; The chemical formula of the shell is (Y _0.999 Ce _0.001 ) ₃ (Al _0.999 Mn _0.001 ) ₅ O ₁₂ ; the particle size of the core body is 2 μm, and the thickness of the shell is 2 μm.

The specific steps for the preparation method of the above-mentioned core-shell structure phosphor are as follows:

(1) Weigh each high-purity Y ₂ O ₃ ( _5.702g ), Al ₂ O ₃ (4.294g) and CeO 2 (0.004) according to the stoichiometric ratio of the corresponding elements in _the chemical formula (Y _0.9995 Ce _0.0005 ) ₃ Al 5 O ₁₂ g) A total of 10g of raw material powder; dissolve the above raw materials in 1.801ml of nitric acid to form a (Y _0.9995 Ce _0.0005 ) ₃ Al ₅ O ₁₂ precursor solution;

(2) After the precursor solution of (Y _0.9995 Ce _0.0005 ) ₃ Al ₅ O ₁₂ is dispersed by ultrasonic waves, add the precipitant urea, stir evenly and let it stand for aging to precipitate (Y _0.9995 Ce _0.0005 ) ₃ Al ₅ O ₁₂ Nucleosome precursor; the added amount of urea is 0.3mol/L;

(3) Weigh each high-purity Y ₂ O ₃ (5.697g), CeO ₂ ( _{0.009g), and Al according to the stoichiometric ratio of the corresponding elements in the chemical (Y 0.999 Ce 0.001 ) 3 ( Al} 0.999 _{Mn 0.001 ) 5 O} 12 ₂ O ₃ (4.288g) and MnCO ₃ (0.010g) raw material powders total 10.004g; dissolve the above raw materials in 1.778mL of nitric acid to form (Y _0.999 Ce _0.001 ) ₃ (Al _0.999 Mn _0.001 ) ₅ O ₁₂ Precursor solution;

(4) Mix the (Y _0.999 Ce _0.001 ) ₃ (Al _0.999 Mn _0.001 ) ₅ O ₁₂ precursor solution and the ammonium bicarbonate mixture as the precipitant into the mixed solution obtained in step (2) in drop form, Stir evenly, collect by filtration, wash with deionized water to remove impurities, and dry at constant temperature to obtain (Y _0.9995 Ce _0.0005 ) ₃ Al ₅ O ₁₂ @(Y _0.999 Ce _0.001 ) ₃ (Al _0.999 Mn _0.001 ) ₅ O ₁₂ core Shell structure phosphor; the ammonium bicarbonate mixture is prepared from ammonia water and ammonium bicarbonate solution with a molar ratio of 1:1.4, in which the mass fraction of ammonia water is 25% and the molar concentration of ammonium bicarbonate solution is 0.5 mol/ L; the constant temperature drying temperature is 55°C and the time is 12h.

Mix the core-shell structure phosphor prepared by the above method and the glass powder with a sieve mesh of 300 mesh and then pour it into the copper mold. The mass ratio between the core-shell structure phosphor and the glass powder is 5:1. Stir evenly before placing It is sintered in a muffle furnace at a sintering temperature of 400°C and a sintering time of 1 hour. The sintered material is cut and polished to obtain a reflective fluorescent device, as shown in Figure 2. The reflective fluorescent device includes luminescent elements in an up and down position. layer and copper sheet, the thickness of the luminescent layer is 0.8mm.

The fluorescent device prepared in this embodiment has a maximum luminous efficiency of 185lm/W, a color temperature of 4300K, and a color rendering index of 92 under laser excitation of 25W/ ^mm2 .

Example 2

A core-shell structure phosphor. The structure is shown in Figure 1. The phosphor includes a core body and a shell wrapped around the core body. The chemical formula of the core body is (Lu _0.999 Ce _0.001 ) ₃ Al ₅ O ₁₂ ; The chemical formula of the shell is (Lu _0.995 Ce _0.005 ) ₃ (Al _0.99 Cr _0.01 ) ₅ O ₁₂ ; the particle size of the core body is 2.5 μm, and the thickness of the shell is 4 μm.

The specific steps for the preparation method of the above-mentioned core-shell structure phosphor are as follows:

(1) Weigh _each high-purity Lu ₂ O ₃ (7.001g), Al ₂ O ₃ (2.993g) and CeO 2 (0.006) according to the stoichiometric ratio of the corresponding elements in _the chemical formula ₍ Lu _0.999 Ce _0.001 ) 3 Al 5 O ₁₂ g) A total of 10g of raw material powder; dissolve the above raw materials in 7.594ml of nitric acid to form a (Lu _0.999 Ce _0.001 ) ₃ Al ₅ O ₁₂ precursor solution;

(2) After the precursor solution of (Lu _0.999 Ce _0.001 ) ₃ Al ₅ O ₁₂ is dispersed by ultrasonic waves, add the precipitant urea, stir evenly and let it stand for aging to precipitate (Lu _0.999 Ce _0.001 ) ₃ Al ₅ O ₁₂ Nucleosome precursor; the added amount of urea is 1 mol/L;

(3) Weigh each high-purity Lu ₂ O ₃ (6.967g), CeO ₂ (0.030g), and Al according to the stoichiometric ratio of the corresponding elements in _the chemical (Lu _0.995 Ce _0.005 ) ₃ (Al _0.99 Cr _0.01 ) ₅ O 12 ₂ O ₃ (2.960g) and Cr ₂ O ₃ (0.045g) raw material powders total 10.002g; the above raw materials were dissolved in 7.437mL of nitric acid to form (Lu _0.995 Ce _0.005 ) ₃ (Al _0.99 Cr _0.01 ) ₅ O ₁₂ precursor solution;

(4) Mix the (Lu _0.995 Ce _0.005 ) ₃ (Al _0.99 Cr _0.01 ) ₅ O ₁₂ precursor solution and the ammonium bicarbonate mixture as the precipitant in dropwise form and add it to the mixed solution obtained in step (2), Stir evenly, collect by filtration, wash with deionized water to remove impurities, and dry at constant temperature to obtain (Lu _0.999 Ce _0.001 ) ₃ Al ₅ O ₁₂ @(Lu _0.995 Ce _0.005 ) ₃ (Al _0.99 Cr _0.01 ) ₅ O ₁₂ core Shell structure phosphor; the ammonium bicarbonate mixture is prepared from ammonia water and ammonium bicarbonate solution with a molar ratio of 1:2, in which the mass fraction of ammonia water is 26% and the molar concentration of ammonium bicarbonate solution is 1.0 mol/ L; the constant temperature drying temperature is 65°C and the time is 18h.

Mix the core-shell structure phosphor prepared by the above method with the 400-mesh glass powder and pour it into a copper mold. The mass ratio between the core-shell structure phosphor and the glass powder is 7:1 and stir evenly. It is then placed in a muffle furnace for sintering. The sintering temperature is 700°C and the sintering time is 2 hours. The sintered material is cut and polished to obtain a reflective fluorescent device. As shown in Figure 2, the reflective fluorescent device includes an up and down position. A luminescent layer and a copper sheet, the thickness of the luminescent layer is 0.5mm.

The fluorescent device prepared in this embodiment has a maximum luminous efficiency of 205lm/W, a color temperature of 3900K, and a color rendering index of 96 under laser excitation of 25W/ ^mm2 .

Example 3

A core-shell structure phosphor. The structure is shown in Figure 1. The phosphor includes a core body and a shell wrapped around the core body. The chemical formula of the core body is (Y _0.9995 Ce _0.005 ) ₃ Al ₅ O ₁₂ ; The chemical formula of the shell is (Y _0.99 Ce _0.01 ) ₃ (Al _0.98 Mn _0.02 ) ₅ O ₁₂ ; the particle size of the core is 3 μm, and the thickness of the shell is 6 μm.

The specific steps for the preparation method of the above-mentioned core-shell structure phosphor are as follows:

(1) Weigh each high-purity Y ₂ O ₃ (5.67g), Al ₂ O ₃ (4.289g) and CeO 2 (0.043) according to the stoichiometric ratio of the corresponding elements in _the chemical formula (Y _0.995 Ce _0.005 ) _{3 Al} 5 O ₁₂ g) A total of 10.002g of raw material powder; dissolve the above raw materials in 1.775ml of nitric acid to form a (Y _0.9995 Ce _0.005 ) ₃ Al ₅ O ₁₂ precursor solution;

(2) After the precursor solution of (Y _0.9995 Ce _0.005 ) ₃ Al ₅ O ₁₂ is dispersed by ultrasonic waves, add the precipitant urea, stir evenly and let it stand for aging to precipitate (Y _0.9995 Ce _0.005 ) ₃ Al ₅ O ₁₂ Nucleosome precursor; the added amount of urea is 2mol/L;

(3) Weigh each high-purity Y ₂ O ₃ ( _5.608g ), CeO ₂ (0.086g), and Al according to the stoichiometric ratio of the corresponding elements in the chemical (Y _0.99 Ce _0.01 ) ₃ (Al _0.98 Mn _0.02 ) ₅ O 12 ₂ O ₃ (4.178g) and MnCO ₃ (0.192g) raw material powders total 10.064g; dissolve the above raw materials in 5.333mL nitric acid to form (Y _0.99 Ce _0.01 ) ₃ (Al _0.98 Mn _0.02 ) ₅ O ₁₂ precursor body solution;

(4) Mix the (Y _0.99 Ce _0.01 ) ₃ (Al _0.98 Mn _0.02 ) ₅ O ₁₂ precursor solution and the ammonium bicarbonate mixture as the precipitant in dropwise form and add it to the mixed solution obtained in step (2), Stir evenly, collect by filtration, wash with deionized water to remove impurities, and dry at constant temperature to obtain (Y _0.9995 Ce _0.005 ) ₃ Al ₅ O ₁₂ @(Y _0.99 Ce _0.01 ) ₃ (Al _0.98 Mn _0.02 ) ₅ O ₁₂ core Shell structure phosphor; the ammonium bicarbonate mixture is prepared from ammonia water and ammonium bicarbonate solution with a molar ratio of 1:3, in which the mass fraction of ammonia water is 28% and the molar concentration of ammonium bicarbonate solution is 1.5 mol/ L; the constant temperature drying temperature is 75°C and the time is 24h.

Mix the core-shell structure phosphor prepared by the above method with the 500-mesh glass powder and pour it into a copper mold. The mass ratio between the core-shell structure phosphor and the glass powder is 10:1 and stir evenly. Afterwards, it is placed in a muffle furnace for sintering. The sintering temperature is 1000°C and the sintering time is 3 hours. The sintered material is cut and polished to obtain a reflective fluorescent device. As shown in Figure 2, the reflective fluorescent device includes an upper and lower position. The thickness of the luminescent layer and the copper sheet is 0.1mm.

See Figure 3, which shows the changes in luminous efficiency and CRI of the fluorescent device prepared in this embodiment under 450 nm laser excitation. Among them, as the laser power density increases from 5W/mm ² to 30W/mm ² , the luminous efficiency LE first increases and then reaches saturation at 240lm/W, and the color rendering index CRI has a small range of change, fluctuating around 98. , indicating that it has good color stability.

The fluorescent device prepared in this embodiment has a maximum luminous efficiency of 240lm/W, a color temperature of 3500K, and a color rendering index of 98 under laser excitation of 25W/ ^mm2 .

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person familiar with the technical field shall, within the technical scope disclosed in the present invention, be within the spirit and principles of the present invention. Any modifications, equivalent substitutions and improvements made within the above shall be included in the protection scope of the present invention.

Claims (8)

1. A core-shell structure phosphor, characterized in that the phosphor includes a core and a shell wrapped around the core. The chemical formula of the core is (Re _1-x Ce _x ) ₃ Al ₅ O ₁₂ , in the formula, Re is Y or Lu, x is the mole percentage of Ce ³⁺ replaced by Y ³⁺ or Lu ³⁺ , 0.0005≤x≤0.005; the chemical formula of the shell is (A _1-y Ce _y ) ₃ (Al _1-z B _z ) ₅ O ₁₂ , in the formula, A is Y or Lu, B is Mn or Cr, y is the mole percentage of Ce ³⁺ replaced by Y ³⁺ or Lu ³⁺ , 0.001≤y≤0.01 , z is the molar percentage of Al ³⁺ replaced by Mn ²⁺ or Cr ³⁺ , 0.001≤z≤0.02. 2. A core-shell structure phosphor according to claim 1, characterized in that the particle size of the core body is 2-3 μm, and the thickness of the shell is 2-6 μm. 3. A method for preparing core-shell structure phosphor according to claim 1 or 2, characterized in that the specific steps are as follows: (1) Using Y ₂ O ₃ /Lu ₂ O ₃ , Ce ₂ O ₃ and Al ₂ O ₃ as raw material powders, according to the stoichiometric ratio of the corresponding elements in the chemical formula (Re _1-x Ce _x ) ₃ Al ₅ O ₁₂ Weigh each raw material, where x is the mole percentage of Ce ³⁺ substituted by Y ³⁺ or Lu ³⁺ , 0.0005≤x≤0.005; dissolve the above raw materials in nitric acid to form (Re _1-x Ce _x ) ₃ Al ₅ O ₁₂ precursor solution; (2) After the precursor solution of (Re _1-x Ce _x ) ₃ Al ₅ O ₁₂ is dispersed by ultrasonic waves, add the precipitant urea, stir evenly and let it stand for aging to precipitate (Re _1-x Ce _x ) ₃ Al ₅ O ₁₂ nuclear body precursor; (3) Using Y ₂ O ₃ /Lu ₂ O ₃ , MnCO ₃ /Cr ₂ O ₃ , Ce ₂ O ₃ and Al ₂ O ₃ as raw material powders, according to the chemical formula (A _1-y Ce _y ) ₃ (Al _{1 -z} B _z ) ₅ The stoichiometric ratio of the corresponding elements in O ₁₂ Weigh each raw material, where y is the mole percentage of Y ³⁺ or Lu ³⁺ replacing Ce ³⁺ position, z is Mn ²⁺ or Cr ³⁺ replacing Al The mole percentage of the ³⁺ position, 0.001≤y≤0.01, 0.001≤z≤0.02; dissolve the above raw materials in nitric acid to form (A _1-y Ce _y ) ₃ (Al _1-z B _z ) ₅ O ₁₂ precursor body solution; (4) Mix the (A _1-y Ce _y ) ₃ (Al _1-z B _z ) ₅ O ₁₂ precursor solution and the ammonium bicarbonate mixture as the precipitant into the solution obtained in step (2) in drop form. into the mixed solution, stir evenly, collect by filtration, wash with deionized water to remove impurities, and dry at constant temperature to obtain (Re _1-x Ce _x ) ₃ Al ₅ O ₁₂ @(A _1-y Ce _y ) ₃ (Al _1-z B _z ) ₅ O ₁₂ core-shell structure phosphor. 4. The method for preparing core-shell structure phosphor according to claim 3, characterized in that in step (2), the added amount of the precipitating agent urea is 0.3-2 mol/L. 5. The preparation method of a core-shell structure phosphor according to claim 3 or 4, characterized in that in step (4), the molar ratio of the ammonium bicarbonate mixture is 1: (1.4~3) It is prepared from ammonia water and ammonium bicarbonate solution, wherein the mass fraction of ammonia water is 25 to 28%, and the molar concentration of ammonium bicarbonate solution is 0.5 to 1.5 mol/L; the constant temperature drying temperature is 55 to 75°C, and the time It is 12~24h. 6. Application of the core-shell structure phosphor according to claim 1 in the preparation of reflective fluorescent devices. The specific application process is: mixing the core-shell structure phosphor according to claim 1 with glass powder and then pouring it into a copper mold. , stir evenly and then place it in a muffle furnace for sintering. Cut and polish the sintered material to obtain a reflective fluorescent device. The reflective fluorescent device includes a luminescent layer and a copper sheet in an upper and lower position. 7. The application of the core-shell structure phosphor according to claim 6 in the preparation of reflective fluorescent devices, characterized in that the sieving mesh number of the glass powder is 300 to 500 mesh, and the core-shell structure phosphor and glass The mass ratio between powders is (5~10):1. 8. The application of the core-shell structure phosphor according to claim 6 or 7 in the preparation of reflective fluorescent devices, characterized in that the sintering temperature is 400-1000°C, the sintering time is 1-3h; the luminescence The layer thickness is 0.1~0.8mm.